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[PATCH net-next v4 0/3] net: devmem: allow rx-buf-size > PAGE_SIZE per binding

by Bobby Eshleman

Every devmem dmabuf binding hands the page_pool PAGE_SIZE niovs today. On NICs that consume one descriptor per netmem, this caps a single RX descriptor at PAGE_SIZE and burns CPU on buffer churn. In this series, we add a bind-time netlink attribute, NETDEV_A_DMABUF_RX_BUF_SIZE, that lets userspace request a larger niov size (power of two >= PAGE_SIZE). Drivers must opt in via queue_mgmt_ops.QCFG_RX_PAGE_SIZE. Selftests use udmabuf, but udmabuf sgtables were previously hardcoded to PAGE_SIZE. This series modifies udmabuf to respect folio sizes in its exported sgtable. The result is that when backing udmabuf with MFD_HUGETLB 2MB pages, the sgtable is populated with 2MB entries, allowing devmem's gen_pool to carve out large (eg. 64K) niovs. Measurements ------------ Setup: kperf devmem RX/TX cuda, 4 flows, 64 MB messages, 60s, dctcp, num-rx-queues=4, dmabuf-rx/tx-size-mb=2048, 10 runs per niov size, mlx5. niov RX dev Gbps RX flow avg Gbps app sys % ----- ---------------- ----------------- ---------------- 4K 300.63 +/- 53.21 75.16 +/- 13.30 54.15 +/- 10.23 16K 321.35 +/- 28.20 80.34 +/- 7.05 41.05 +/- 8.87 32K 347.63 +/- 2.20 86.91 +/- 0.55 44.54 +/- 3.51 64K 332.11 +/- 14.26 83.03 +/- 3.56 35.47 +/- 3.11 RX app sys % drops ~19% from 4K to 64K. kperf support (not yet merged): https://github.com/facebookexperimental/kperf/commit/8837577f920876bce6986e… Signed-off-by: Bobby Eshleman <bobbyeshleman(a)meta.com> --- Changes in v4: - ncdevmem: fix the possible overflow in ncdevmem (Sashiko) - drop the udmabuf patch because the fix is now already in net-next - silenced two pylint complaints in devmem_lib.py - Link to v3: https://lore.kernel.org/r/20260612-tcpdm-large-niovs-v3-0-a3b693e76fcb@meta… Changes in v3: - fix a bunch of non-reverse christmas tree declarations (Stan) - remove extra uint32 cast for getpagesize() (Stan) - remove overzealous strtoul checking (Stan) - remove value checks that the kernel already performs on rx_buf_size (Stan) - Link to v2: https://lore.kernel.org/r/20260611-tcpdm-large-niovs-v2-0-ee2bf15e7523@meta… Changes in v2: - Use NL_SET_ERR_MSG_FMT for sg alignment failure details (Stan) - Keep -E2BIG (not a direct ask, but seemed preferred, Stan) - Update udmabuf commit message and comments explaining why "one sg ent per folio" is useful (Christian) - Set/restore nr_hugepages in py harness (Stan) - Link to v1: https://lore.kernel.org/r/20260603-tcpdm-large-niovs-v1-0-f37a4ac6726c@meta… --- Bobby Eshleman (3): net: devmem: allow rx-buf-size > PAGE_SIZE per dmabuf binding selftests/net: ncdevmem: add -b option to set rx-buf-size on bind selftests/net: devmem.py: add check_rx_large_niov Documentation/netlink/specs/netdev.yaml | 8 +++ include/uapi/linux/netdev.h | 1 + net/core/devmem.c | 55 +++++++++++--------- net/core/devmem.h | 13 +++-- net/core/netdev-genl-gen.c | 5 +- net/core/netdev-genl.c | 19 ++++++- tools/include/uapi/linux/netdev.h | 1 + tools/testing/selftests/drivers/net/hw/devmem.py | 12 ++++- .../testing/selftests/drivers/net/hw/devmem_lib.py | 59 +++++++++++++++++++++- tools/testing/selftests/drivers/net/hw/ncdevmem.c | 36 +++++++++++-- .../testing/selftests/drivers/net/hw/nk_devmem.py | 11 +++- 11 files changed, 180 insertions(+), 40 deletions(-) --- base-commit: 805185b7c7a1069e407b6f7b3bc98e44d415f484 change-id: 20260602-tcpdm-large-niovs-56523a3a1077 Best regards, -- Bobby Eshleman <bobbyeshleman(a)meta.com>

1 month, 1 week

[PATCH] dma-buf: fix stale @lock references in struct dma_buf documentation

by Xiang Gao

From: Xiang Gao <gaoxiang17(a)xiaomi.com> The kernel-doc comments for vmapping_counter and vmap_ptr in struct dma_buf reference "@lock" as the protecting lock, but struct dma_buf no longer has a "lock" member. The mutex was removed in favor of using the dma_resv lock exclusively. The implementation correctly uses dma_resv_assert_held(dmabuf->resv) in dma_buf_vmap() and dma_buf_vunmap(), so update the documentation to reference @resv instead. Signed-off-by: gaoxiang17 <gaoxiang17(a)xiaomi.com> --- include/linux/dma-buf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 133b9e637b55..ef6d93fd7a2c 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -322,13 +322,13 @@ struct dma_buf { * @vmapping_counter: * * Used internally to refcnt the vmaps returned by dma_buf_vmap(). - * Protected by @lock. + * Protected by @resv. */ unsigned vmapping_counter; /** * @vmap_ptr: - * The current vmap ptr if @vmapping_counter > 0. Protected by @lock. + * The current vmap ptr if @vmapping_counter > 0. Protected by @resv. */ struct iosys_map vmap_ptr; -- 2.34.1

1 month, 2 weeks

Drive Mad unblocked

by Williamia Hight

Exploring the World of Vehicle Engineering in Drive Mad Drive Mad changes how we think about traditional racing games. You are not just pushing a gas pedal to win. You are managing the weight and the center of gravity of your machine. Every car has a different personality in this game. Some are heavy and stable while others are light and bouncy. Choosing the right vehicle for the level is your first strategic step. The levels in Drive Mad are more like mechanical puzzles than race tracks. You have to understand the triggers that move the obstacles. A platform might drop only when you reach a certain point. You must time your approach to avoid the trap. It requires you to observe the environment before you take action. This brain work makes the game much more satisfying than simple racing titles. You will encounter many moments of frustration during your progress. This is the main appeal of the game for many players. You learn from every mistake you make on the road. Eventually you find the perfect rhythm to clear the most difficult gaps. The feeling of success after a hard level is unmatched. Keep your focus sharp and your hands ready to drive. https://drivinggames.io

1 month, 2 weeks

[PATCH] dma-buf: explicitely forbid exposing pages from get_user_pages()

by Christian König

We recently had another incident where two drivers put pages they got from get_user_pages() into a DMA-buf and cause quite a number of problems. Explicitely document that this is not something exporters can do. Signed-off-by: Christian König <christian.koenig(a)amd.com> --- drivers/dma-buf/dma-buf.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 71f37544a5c6..aa5af4f439c2 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -685,6 +685,14 @@ static struct file *dma_buf_getfile(size_t size, int flags) * * For the detailed semantics exporters are expected to implement see * &dma_buf_ops. + * + * It is explicitely forbidden for exporters to expose buffers they don't "own" + * as DMA-buf. This includes pages acquired by get_user_pages() or other import + * mechanism. Not following this rule can create numerous security problems. + * + * It is also strongly discouraged to expose the same backing store through + * multiple DMA-bufs at the same time. This eventually creates aliasing and + * cache coherency problems which are extremely hard to debug and fix. */ /** -- 2.43.0

1 month, 2 weeks

[PATCH v19 00/40] DEPT(DEPendency Tracker)

by Byungchul Park

Hi Linus and folks, DEPT(DEPendency Tracker) is a runtime deadlock detection framework that sees what lockdep cannot. I'm thrilled to share that DEPT has moved beyond theory and is now catching real deadlocks in the wild: https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SA… https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.pa… https://lore.kernel.org/all/b6e00e77-4a8c-4e05-ab79-266bf05fcc2d@igalia.com/ I've added comprehensive documentation explaining DEPT's design and usage. Getting started is as simple as enabling CONFIG_DEPT and watching dmesg. THE PROBLEM LOCKDEP CANNOT SOLVE -------------------------------- Lockdep has been our trusted deadlock detector for two decades, but it has a fundamental blind spot: it tracks lock acquisition order, not the actual waits and events that cause deadlocks. This means lockdep misses: * Deadlocks involving folio locks (not released within the context) * Cross-context synchronization like wait_for_completion()/complete() * DMA fence waits, RCU waits, and general waitqueue patterns * Any synchronization primitive outside the classic lock/unlock model Consider this real deadlock pattern that lockdep cannot detect: context X context Y context Z mutex_lock A folio_lock B folio_lock B <- DEADLOCK mutex_lock A <- DEADLOCK folio_unlock B folio_unlock B mutex_unlock A mutex_unlock A Lockdep sees lock acquisitions. DEPT sees the actual dependency: "mutex_unlock A in context Y cannot happen until folio_lock B is awakened by the owner's folio_unlock B, and vice versa in context Z." It's a circular dependency that means deadlock. THE DEPT APPROACH ----------------- DEPT asks a simpler question: "What is this context waiting for, and what event will wake it up?" Every deadlock is fundamentally about unreachable events. DEPT tracks: [S] Where an event context begins (the code path that will trigger an event) [W] Where a wait for another event apears between [S] and [E] [E] Where the event for [S] occurs By building a dependency graph of "[E] cannot occur until the event that [W] waits for occurs", DEPT detects circular dependencies regardless of the underlying synchronization primitives involved. WHAT DEPT BRINGS TO THE TABLE ----------------------------- * Universal coverage: Works with any wait/event-based synchronization, not just locks * Correct read-lock handling: No more blind spots for read-side dependencies * Continuous operation: Unlike lockdep, DEPT keeps running after reports, catching multiple deadlocks in a single session * Clean annotation API: Simple, intuitive interfaces for subsystem maintainers to refine detection * Battle-tested: Already catching real deadlocks as the links above demonstrate FALSE POSITIVES: THE HONEST CONVERSATION ---------------------------------------- Like any powerful detection tool, DEPT faces the false positive challenge. This is not unique to DEPT — lockdep spent years building its annotation infrastructure (lock classes, subclasses, lockdep_map) to separate real bugs from intentional patterns. DEPT is on the same journey. We have: * Event site recovery: Declare when an event has fallback paths * Subclass-based classification: Distinguish per-CPU, per-device, and modality-specific waits * Page usage tracking: Separate block device mappings from regular file mappings to avoid spurious reports (currently being worked on) But comprehensive annotation requires subsystem maintainer expertise. This is where I need your help. THE PATH TO MAINLINE -------------------- DEPT is marked EXPERIMENTAL in Kconfig for a reason. Like lockdep, it will mature through collaboration: 1. Core framework: Stabilized and ready for review 2. Subsystem pilots: Working with maintainers to add annotations where they matter most (mm, block, drm, networking, ...) 3. Gradual enablement: DEPT and lockdep coexist; DEPT takes over dependency checking when ready I am not proposing to replace lockdep. Lockdep's lock usage validation remains invaluable. The vision is: LOCKDEP: Validates correct lock usage | v DEPT: Performs dependency checking with full wait/event coverage WHY MERGE NOW? -------------- Some might suggest: "Fix all false positives out-of-tree first." But the affected subsystems span the entire kernel. Like lockdep's two-decade annotation journey, DEPT needs mainline visibility for: * Proper annotation placement (maintainers know their code best) * Real-world testing across configurations and workloads * Incremental improvement through community feedback CONFIG_DEPT is opt-in. It won't affect your default kernel build. But for those debugging complex synchronization issues, DEPT is ready to help today. ACKNOWLEDGMENTS --------------- This work would not be possible without: Harry Yoo <harry.yoo(a)oracle.com> Gwan-gyeong Mun <gwan-gyeong.mun(a)intel.com> Yunseong Kim <ysk(a)kzalloc.com> Yeoreum Yun <yeoreum.yun(a)arm.com> And the countless kernel developers whose lockdep annotations over two decades showed us the path forward. FAQ --- Q. Isn't this the cross-release feature that got reverted? A. Cross-release (commit b09be676e0ff2) attempted to extend lockdep with wait/event tracking. It found real bugs but introduced false positives that masked further issues. DEPT learns from that experience with a cleaner design and flexible reporting that makes false positives less disruptive. Q. Why not build DEPT into lockdep? A. Lockdep is stable, battle-tested code. I chose separation because while DEPT borrows BFS and hashing ideas, the wait/event model requires rebuilding from scratch. Lockdep was designed for lock acquisition order — retrofitting it would risk its stability. Q. Will DEPT replace lockdep? A. No. Lockdep validates correct lock usage — that's not going away. DEPT supersedes only the dependency-checking logic when mature. Q. Should we merge DEPT now or wait for more annotations out-of-tree? A. Now. The annotation journey requires mainline collaboration. Lockdep didn't become useful overnight — it grew through maintainer contributions. DEPT needs the same path. Q. What if I enable DEPT and get false positives? A. That's the point — report them. Work with us to add annotations that distinguish your intentional patterns from real deadlocks. This is how lockdep became indispensable, and it's how DEPT will too. GETTING STARTED --------------- 1. Enable CONFIG_DEPT (EXPERIMENTAL) 2. Boot your kernel 3. Check dmesg for DEPT reports 4. Read Documentation/dev-tools/dept.rst for interpretation DEPT is a tool for understanding your code's synchronization behavior. Even if you never see a deadlock report, the visibility it provides is invaluable. I look forward to your feedback, patches, and collaboration. Let's make DEPT as indispensable to kernel developers as lockdep has been. --- Changes from v18: 1. Rebase on v7.0. 2. Add 'Reviewed-by: Jeff Layton <jlayton(a)kernel.org>' on 37th patch, 'SUNRPC: relocate struct rcu_head to the first field of struct rpc_xprt'. (thanks to Jeff Layton) 3. Refine and supplement dept documents and comments, and fix typos. (feedbacked by Bagas Sanjaya and Yunseong Kim) 4. Add __rust_helper to rust_helper_wait_for_completion(). (feedbacked by Dirk Behme) 5. Remove the part supporting recover events tracking - I will keep maintaining it out of tree tho - as it unnecessarily complicates the initial DEPT patchset and significantly increases the review burden. 6. Get rid of 'extern' keyword with function declarations. (feedbacked by Petr Pavlu) Changes from v17: 1. Rebase on the mainline as of 2025 Dec 5. 2. Convert the documents' format from txt to rst. (feedbacked by Jonathan Corbet and Bagas Sanjaya) 3. Move the documents from 'Documentation/dependency' to 'Documentation/dev-tools'. (feedbakced by Jonathan Corbet) 4. Improve the documentation. (feedbacked by NeilBrown) 5. Use a common function, enter_from_user_mode(), instead of arch specific code, to notice context switch from user mode. (feedbacked by Dave Hansen, Mark Rutland, and Mark Brown) 6. Resolve the header dependency issue by using dept's internal header, instead of relocating 'struct llist_{head,node}' to another header. (feedbacked by Greg KH) 7. Improve page(or folio) usage type APIs. 8. Add rust helper for wait_for_completion(). (feedbacked by Guangbo Cui, Boqun Feng, and Danilo Krummrich) 9. Refine some commit messages. Changes from v16: 1. Rebase on v6.17. 2. Fix a false positive from rcu (by Yunseong Kim) 3. Introduce APIs to set page's usage, dept_set_page_usage() and dept_reset_page_usage() to avoid false positives. 4. Consider lock_page() as a potential wait unconditionally. 5. Consider folio_lock_killable() as a potential wait unconditionally. 6. Add support for tracking PG_writeback waits and events. 7. Fix two build errors due to the additional debug information added by dept. (by Yunseong Kim) Changes from v15: 1. Fix typo and improve comments and commit messages (feedbacked by ALOK TIWARI, Waiman Long, and kernel test robot). 2. Do not stop dept on detection of cicular dependency of recover event, allowing to keep reporting. 3. Add SK hynix to copyright. 4. Consider folio_lock() as a potential wait unconditionally. 5. Fix Kconfig dependency bug (feedbacked by kernel test rebot). 6. Do not suppress reports that involve classes even that have already involved in other reports, allowing to keep reporting. Changes from v14: 1. Rebase on the current latest, v6.15-rc6. 2. Refactor dept code. 3. With multi event sites for a single wait, even if an event forms a circular dependency, the event can be recovered by other event(or wake up) paths. Even though informing the circular dependency is worthy but it should be suppressed once informing it, if it doesn't lead an actual deadlock. So introduce APIs to annotate the relationship between event site and recover site, that are, event_site() and dept_recover_event(). 4. wait_for_completion() worked with dept map embedded in struct completion. However, it generates a few false positves since all the waits using the instance of struct completion, share the map and key. To avoid the false positves, make it not to share the map and key but each wait_for_completion() caller have its own key by default. Of course, external maps also can be used if needed. 5. Fix a bug about hardirq on/off tracing. 6. Implement basic unit test for dept. 7. Add more supports for dma fence synchronization. 8. Add emergency stop of dept e.g. on panic(). 9. Fix false positives by mmu_notifier_invalidate_*(). 10. Fix recursive call bug by DEPT_WARN_*() and DEPT_STOP(). 11. Fix trivial bugs in DEPT_WARN_*() and DEPT_STOP(). 12. Fix a bug that a spin lock, dept_pool_spin, is used in both contexts of irq disabled and enabled without irq disabled. 13. Suppress reports with classes, any of that already have been reported, even though they have different chains but being barely meaningful. 14. Print stacktrace of the wait that an event is now waking up, not only stacktrace of the event. 15. Make dept aware of lockdep_cmp_fn() that is used to avoid false positives in lockdep so that dept can also avoid them. 16. Do do_event() only if there are no ecxts have been delimited. 17. Fix a bug that was not synchronized for stage_m in struct dept_task, using a spin lock, dept_task()->stage_lock. 18. Fix a bug that dept didn't handle the case that multiple ttwus for a single waiter can be called at the same time e.i. a race issue. 19. Distinguish each kernel context from others, not only by system call but also by user oriented fault so that dept can work with more accuracy information about kernel context. That helps to avoid a few false positives. 20. Limit dept's working to x86_64 and arm64. Changes from v13: 1. Rebase on the current latest version, v6.9-rc7. 2. Add 'dept' documentation describing dept APIs. Changes from v12: 1. Refine the whole document for dept. 2. Add 'Interpret dept report' section in the document, using a deadlock report obtained in practice. Hope this version of document helps guys understand dept better. https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SA… https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.pa… Changes from v11: 1. Add 'dept' documentation describing the concept of dept. 2. Rewrite the commit messages of the following commits for using weaker lockdep annotation, for better description. fs/jbd2: Use a weaker annotation in journal handling cpu/hotplug: Use a weaker annotation in AP thread (feedbacked by Thomas Gleixner) Changes from v10: 1. Fix noinstr warning when building kernel source. 2. dept has been reporting some false positives due to the folio lock's unfairness. Reflect it and make dept work based on dept annotaions instead of just wait and wake up primitives. 3. Remove the support for PG_writeback while working on 2. I will add the support later if needed. 4. dept didn't print stacktrace for [S] if the participant of a deadlock is not lock mechanism but general wait and event. However, it made hard to interpret the report in that case. So add support to print stacktrace of the requestor who asked the event context to run - usually a waiter of the event does it just before going to wait state. 5. Give up tracking raw_local_irq_{disable,enable}() since it totally messed up dept's irq tracking. So make it work in the same way as lockdep does. I will consider it once any false positives by those are observed again. 6. Change the manual rwsem_acquire_read(->j_trans_commit_map) annotation in fs/jbd2/transaction.c to the try version so that it works as much as it exactly needs. 7. Remove unnecessary 'inline' keyword in dept.c and add '__maybe_unused' to a needed place. Changes from v9: 1. Fix a bug. SDT tracking didn't work well because of my big mistake that I should've used waiter's map to indentify its class but it had been working with waker's one. FYI, PG_locked and PG_writeback weren't affected. They still worked well. (reported by YoungJun) Changes from v8: 1. Fix build error by adding EXPORT_SYMBOL(PG_locked_map) and EXPORT_SYMBOL(PG_writeback_map) for kernel module build - appologize for that. (reported by kernel test robot) 2. Fix build error by removing header file's circular dependency that was caused by "atomic.h", "kernel.h" and "irqflags.h", which I introduced - appolgize for that. (reported by kernel test robot) Changes from v7: 1. Fix a bug that cannot track rwlock dependency properly, introduced in v7. (reported by Boqun and lockdep selftest) 2. Track wait/event of PG_{locked,writeback} more aggressively assuming that when a bit of PG_{locked,writeback} is cleared there might be waits on the bit. (reported by Linus, Hillf and syzbot) 3. Fix and clean bad style code e.i. unnecessarily introduced a randome pattern and so on. (pointed out by Linux) 4. Clean code for applying dept to wait_for_completion(). Changes from v6: 1. Tie to task scheduler code to track sleep and try_to_wake_up() assuming sleeps cause waits, try_to_wake_up()s would be the events that those are waiting for, of course with proper dept annotations, sdt_might_sleep_weak(), sdt_might_sleep_strong() and so on. For these cases, class is classified at sleep entrance rather than the synchronization initialization code. Which would extremely reduce false alarms. 2. Remove the dept associated instance in each page struct for tracking dependencies by PG_locked and PG_writeback thanks to the 1. work above. 3. Introduce CONFIG_dept_AGGRESIVE_TIMEOUT_WAIT to suppress reports that waits with timeout set are involved, for those who don't like verbose reporting. 4. Add a mechanism to refill the internal memory pools on running out so that dept could keep working as long as free memory is available in the system. 5. Re-enable tracking hashed-waitqueue wait. That's going to no longer generate false positives because class is classified at sleep entrance rather than the waitqueue initailization. 6. Refactor to make it easier to port onto each new version of the kernel. 7. Apply dept to dma fence. 8. Do trivial optimizaitions. Changes from v5: 1. Use just pr_warn_once() rather than WARN_ONCE() on the lack of internal resources because WARN_*() printing stacktrace is too much for informing the lack. (feedback from Ted, Hyeonggon) 2. Fix trivial bugs like missing initializing a struct before using it. 3. Assign a different class per task when handling onstack variables for waitqueue or the like. Which makes dept distinguish between onstack variables of different tasks so as to prevent false positives. (reported by Hyeonggon) 4. Make dept aware of even raw_local_irq_*() to prevent false positives. (reported by Hyeonggon) 5. Don't consider dependencies between the events that might be triggered within __schedule() and the waits that requires __schedule(), real ones. (reported by Hyeonggon) 6. Unstage the staged wait that has prepare_to_wait_event()'ed *and* yet to get to __schedule(), if we encounter __schedule() in-between for another sleep, which is possible if e.g. a mutex_lock() exists in 'condition' of ___wait_event(). 7. Turn on CONFIG_PROVE_LOCKING when CONFIG_DEPT is on, to rely on the hardirq and softirq entrance tracing to make dept more portable for now. Changes from v4: 1. Fix some bugs that produce false alarms. 2. Distinguish each syscall context from another *for arm64*. 3. Make it not warn it but just print it in case dept ring buffer gets exhausted. (feedback from Hyeonggon) 4. Explicitely describe "EXPERIMENTAL" and "dept might produce false positive reports" in Kconfig. (feedback from Ted) Changes from v3: 1. dept shouldn't create dependencies between different depths of a class that were indicated by *_lock_nested(). dept normally doesn't but it does once another lock class comes in. So fixed it. (feedback from Hyeonggon) 2. dept considered a wait as a real wait once getting to __schedule() even if it has been set to TASK_RUNNING by wake up sources in advance. Fixed it so that dept doesn't consider the case as a real wait. (feedback from Jan Kara) 3. Stop tracking dependencies with a map once the event associated with the map has been handled. dept will start to work with the map again, on the next sleep. Changes from v2: 1. Disable dept on bit_wait_table[] in sched/wait_bit.c reporting a lot of false positives, which is my fault. Wait/event for bit_wait_table[] should've been tagged in a higher layer for better work, which is a future work. (feedback from Jan Kara) 2. Disable dept on crypto_larval's completion to prevent a false positive. Changes from v1: 1. Fix coding style and typo. (feedback from Steven) 2. Distinguish each work context from another in workqueue. 3. Skip checking lock acquisition with nest_lock, which is about correct lock usage that should be checked by lockdep. Changes from RFC(v0): 1. Prevent adding a wait tag at prepare_to_wait() but __schedule(). (feedback from Linus and Matthew) 2. Use try version at lockdep_acquire_cpus_lock() annotation. 3. Distinguish each syscall context from another. Byungchul Park (39): dept: implement DEPT(DEPendency Tracker) dept: add single event dependency tracker APIs dept: add lock dependency tracker APIs dept: tie to lockdep and IRQ tracing dept: add proc knobs to show stats and dependency graph dept: distinguish each kernel context from another dept: distinguish each work from another dept: add a mechanism to refill the internal memory pools on running out dept: record the latest one out of consecutive waits of the same class dept: apply sdt_might_sleep_{start,end}() to wait_for_completion()/complete() dept: apply sdt_might_sleep_{start,end}() to swait dept: apply sdt_might_sleep_{start,end}() to waitqueue wait dept: apply sdt_might_sleep_{start,end}() to hashed-waitqueue wait dept: apply sdt_might_sleep_{start,end}() to dma fence dept: track timeout waits separately with a new Kconfig dept: apply timeout consideration to wait_for_completion()/complete() dept: apply timeout consideration to swait dept: apply timeout consideration to waitqueue wait dept: apply timeout consideration to hashed-waitqueue wait dept: apply timeout consideration to dma fence wait dept: make dept able to work with an external wgen dept: track PG_locked with dept dept: print staged wait's stacktrace on report locking/lockdep: prevent various lockdep assertions when lockdep_off()'ed dept: add documents for dept cpu/hotplug: use a weaker annotation in AP thread dept: assign dept map to mmu notifier invalidation synchronization dept: assign unique dept_key to each distinct dma fence caller dept: make dept aware of lockdep_set_lock_cmp_fn() annotation dept: make dept stop from working on debug_locks_off() dept: assign unique dept_key to each distinct wait_for_completion() caller completion, dept: introduce init_completion_dmap() API dept: call dept_hardirqs_off() in local_irq_*() regardless of irq state dept: introduce APIs to set page usage and use subclasses_evt for the usage dept: track PG_writeback with dept SUNRPC: relocate struct rcu_head to the first field of struct rpc_xprt mm: percpu: increase PERCPU_DYNAMIC_SIZE_SHIFT on DEPT and large PAGE_SIZE rust: completion: Add __rust_helper to rust_helper_wait_for_completion() dept: implement a basic unit test for dept Yunseong Kim (1): rcu/update: fix same dept key collision between various types of RCU Documentation/dev-tools/dept.rst | 905 ++++++++ Documentation/dev-tools/dept_api.rst | 124 + Documentation/dev-tools/index.rst | 2 + drivers/dma-buf/dma-fence.c | 23 +- include/linux/completion.h | 124 +- include/linux/dept.h | 267 +++ include/linux/dept_ldt.h | 78 + include/linux/dept_sdt.h | 68 + include/linux/dept_unit_test.h | 61 + include/linux/dma-fence.h | 74 +- include/linux/hardirq.h | 3 + include/linux/irq-entry-common.h | 4 + include/linux/irqflags.h | 21 +- include/linux/local_lock_internal.h | 1 + include/linux/lockdep.h | 105 +- include/linux/lockdep_types.h | 3 + include/linux/mm_types.h | 4 + include/linux/mmu_notifier.h | 26 + include/linux/mutex.h | 1 + include/linux/page-flags.h | 217 +- include/linux/pagemap.h | 37 +- include/linux/percpu-rwsem.h | 2 +- include/linux/percpu.h | 4 + include/linux/rcupdate_wait.h | 13 +- include/linux/rtmutex.h | 1 + include/linux/rwlock_types.h | 1 + include/linux/rwsem.h | 1 + include/linux/sched.h | 111 + include/linux/seqlock.h | 2 +- include/linux/spinlock_types_raw.h | 3 + include/linux/srcu.h | 2 +- include/linux/sunrpc/xprt.h | 9 +- include/linux/swait.h | 3 + include/linux/wait.h | 3 + include/linux/wait_bit.h | 3 + init/init_task.c | 2 + init/main.c | 2 + kernel/Makefile | 1 + kernel/cpu.c | 2 +- kernel/dependency/Makefile | 5 + kernel/dependency/dept.c | 3222 ++++++++++++++++++++++++++ kernel/dependency/dept_hash.h | 10 + kernel/dependency/dept_internal.h | 314 +++ kernel/dependency/dept_object.h | 13 + kernel/dependency/dept_proc.c | 94 + kernel/dependency/dept_unit_test.c | 149 ++ kernel/exit.c | 1 + kernel/fork.c | 2 + kernel/locking/lockdep.c | 33 + kernel/module/main.c | 2 + kernel/rcu/rcu.h | 1 + kernel/rcu/update.c | 5 +- kernel/sched/completion.c | 62 +- kernel/sched/core.c | 9 + kernel/workqueue.c | 3 + lib/Kconfig.debug | 48 + lib/debug_locks.c | 2 + lib/locking-selftest.c | 2 + mm/filemap.c | 38 + mm/mm_init.c | 3 + mm/mmu_notifier.c | 31 +- rust/helpers/completion.c | 5 + 62 files changed, 6247 insertions(+), 120 deletions(-) create mode 100644 Documentation/dev-tools/dept.rst create mode 100644 Documentation/dev-tools/dept_api.rst create mode 100644 include/linux/dept.h create mode 100644 include/linux/dept_ldt.h create mode 100644 include/linux/dept_sdt.h create mode 100644 include/linux/dept_unit_test.h create mode 100644 kernel/dependency/Makefile create mode 100644 kernel/dependency/dept.c create mode 100644 kernel/dependency/dept_hash.h create mode 100644 kernel/dependency/dept_internal.h create mode 100644 kernel/dependency/dept_object.h create mode 100644 kernel/dependency/dept_proc.c create mode 100644 kernel/dependency/dept_unit_test.c base-commit: 028ef9c96e96197026887c0f092424679298aae8 -- 2.17.1

1 month, 2 weeks

Re: Wordle Unlimited Guide for Endless Word Puzzle Fun

by sloplinda＠gmail.com

Most runs in Crossy Road don’t end in panic or chaos, they end in that quiet realization that you made a decision a little too early or a little too confidently. Try now https://crossyroad2.io

1 month, 2 weeks

[PATCH v1] i2c: qcom-geni: Add dynamic transfer timeout based on transfer length and frequency

by Aniket Randive

The driver uses a static XFER_TIMEOUT of HZ (1 second) for all transfers regardless of message length or bus frequency, causing unnecessary delays on error paths. Compute the timeout dynamically from message length and bus frequency with a 10x safety margin over the theoretical wire time and a 300ms floor. For GPI multi-descriptor transfers, use the maximum message length across all queued messages as the per-completion timeout. Signed-off-by: Aniket Randive <aniket.randive(a)oss.qualcomm.com> --- arch/arm64/configs/defconfig | 54 +++--------------------------- drivers/i2c/busses/i2c-qcom-geni.c | 37 +++++++++++++++----- 2 files changed, 33 insertions(+), 58 deletions(-) diff --git a/arch/arm64/configs/defconfig b/arch/arm64/configs/defconfig index faf146441f97..841108ae2d01 100644 --- a/arch/arm64/configs/defconfig +++ b/arch/arm64/configs/defconfig @@ -32,7 +32,6 @@ CONFIG_KALLSYMS_ALL=y CONFIG_PROFILING=y CONFIG_KEXEC=y CONFIG_KEXEC_FILE=y -CONFIG_CRASH_DUMP=y CONFIG_ARCH_ACTIONS=y CONFIG_ARCH_AIROHA=y CONFIG_ARCH_SUNXI=y @@ -123,10 +122,8 @@ CONFIG_ACPI_APEI_MEMORY_FAILURE=y CONFIG_ACPI_APEI_EINJ=y CONFIG_VIRTUALIZATION=y CONFIG_KVM=y -CONFIG_JUMP_LABEL=y CONFIG_MODULES=y CONFIG_MODULE_UNLOAD=y -CONFIG_IOSCHED_BFQ=y CONFIG_BLK_INLINE_ENCRYPTION=y # CONFIG_CORE_DUMP_DEFAULT_ELF_HEADERS is not set # CONFIG_COMPAT_BRK is not set @@ -137,19 +134,15 @@ CONFIG_MEMORY_FAILURE=y CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_NET=y CONFIG_PACKET=y -CONFIG_UNIX=y -CONFIG_INET=y CONFIG_IP_MULTICAST=y CONFIG_IP_PNP=y CONFIG_IP_PNP_DHCP=y CONFIG_IP_PNP_BOOTP=y -CONFIG_IPV6=y CONFIG_NETFILTER=y CONFIG_BRIDGE_NETFILTER=m CONFIG_NF_CONNTRACK=m CONFIG_NF_CONNTRACK_EVENTS=y CONFIG_NETFILTER_XT_MARK=m -CONFIG_NETFILTER_XT_TARGET_CHECKSUM=m CONFIG_NETFILTER_XT_TARGET_LOG=m CONFIG_NETFILTER_XT_MATCH_ADDRTYPE=m CONFIG_NETFILTER_XT_MATCH_CONNTRACK=m @@ -198,7 +191,6 @@ CONFIG_BT_QCOMSMD=m CONFIG_BT_NXPUART=m CONFIG_CFG80211=m CONFIG_MAC80211=m -CONFIG_MAC80211_LEDS=y CONFIG_RFKILL=m CONFIG_RFKILL_GPIO=m CONFIG_NET_9P=m @@ -253,8 +245,6 @@ CONFIG_PCIE_LAYERSCAPE_GEN4=y CONFIG_PCI_ENDPOINT=y CONFIG_PCI_ENDPOINT_CONFIGFS=y CONFIG_PCI_EPF_TEST=m -CONFIG_PCI_PWRCTRL_GENERIC=m -CONFIG_POWER_SEQUENCING_PCIE_M2=m CONFIG_DEVTMPFS=y CONFIG_DEVTMPFS_MOUNT=y CONFIG_FW_LOADER_USER_HELPER=y @@ -262,9 +252,7 @@ CONFIG_HISILICON_LPC=y CONFIG_IMX_AIPSTZ=m CONFIG_TEGRA_ACONNECT=m CONFIG_MHI_BUS_PCI_GENERIC=m -CONFIG_ARM_SCMI_PROTOCOL=y CONFIG_ARM_SCPI_PROTOCOL=y -CONFIG_RASPBERRYPI_FIRMWARE=y CONFIG_INTEL_STRATIX10_SERVICE=y CONFIG_INTEL_STRATIX10_RSU=m CONFIG_MTK_ADSP_IPC=m @@ -303,7 +291,6 @@ CONFIG_MTD_SPI_NOR=y CONFIG_MTD_UBI=m CONFIG_MTD_HYPERBUS=m CONFIG_HBMC_AM654=m -CONFIG_OF_OVERLAY=y CONFIG_BLK_DEV_LOOP=y CONFIG_BLK_DEV_NBD=m CONFIG_VIRTIO_BLK=y @@ -336,7 +323,6 @@ CONFIG_AHCI_XGENE=y CONFIG_AHCI_QORIQ=y CONFIG_SATA_SIL24=y CONFIG_SATA_RCAR=y -CONFIG_PATA_PLATFORM=y CONFIG_PATA_OF_PLATFORM=y CONFIG_MD=y CONFIG_BLK_DEV_MD=m @@ -423,7 +409,6 @@ CONFIG_MLX5_CORE_EN=y # CONFIG_NET_VENDOR_NETRONOME is not set # CONFIG_NET_VENDOR_NVIDIA is not set # CONFIG_NET_VENDOR_OKI is not set -# CONFIG_NET_VENDOR_PACKET_ENGINES is not set # CONFIG_NET_VENDOR_QLOGIC is not set # CONFIG_NET_VENDOR_BROCADE is not set CONFIG_QCOM_EMAC=m @@ -629,7 +614,7 @@ CONFIG_I2C_OWL=y CONFIG_I2C_APPLE=m CONFIG_I2C_PXA=y CONFIG_I2C_QCOM_CCI=m -CONFIG_I2C_QCOM_GENI=m +CONFIG_I2C_QCOM_GENI=y CONFIG_I2C_QUP=y CONFIG_I2C_RIIC=y CONFIG_I2C_RK3X=y @@ -749,6 +734,7 @@ CONFIG_POWER_RESET_SYSCON=y CONFIG_POWER_RESET_SYSCON_POWEROFF=y CONFIG_SYSCON_REBOOT_MODE=y CONFIG_NVMEM_REBOOT_MODE=m +CONFIG_POWER_SEQUENCING_PCIE_M2=m CONFIG_BATTERY_QCOM_BATTMGR=m CONFIG_BATTERY_SBS=m CONFIG_BATTERY_BQ27XXX=y @@ -787,7 +773,6 @@ CONFIG_MTK_LVTS_THERMAL=m CONFIG_BCM2711_THERMAL=m CONFIG_BCM2835_THERMAL=m CONFIG_BRCMSTB_THERMAL=m -CONFIG_EXYNOS_THERMAL=y CONFIG_RCAR_THERMAL=y CONFIG_RCAR_GEN3_THERMAL=y CONFIG_RZG2L_THERMAL=y @@ -959,7 +944,6 @@ CONFIG_DRM=m CONFIG_DRM_HDLCD=m CONFIG_DRM_MALI_DISPLAY=m CONFIG_DRM_KOMEDA=m -CONFIG_DRM_DISPLAY_CONNECTOR=m CONFIG_DRM_FSL_LDB=m CONFIG_DRM_I2C_NXP_TDA998X=m CONFIG_DRM_ITE_IT6263=m @@ -1057,15 +1041,12 @@ CONFIG_DRM_ZYNQMP_DPSUB=m CONFIG_DRM_ZYNQMP_DPSUB_AUDIO=y CONFIG_FB=y CONFIG_FB_EFI=y -CONFIG_FB_MODE_HELPERS=y CONFIG_BACKLIGHT_PWM=m CONFIG_BACKLIGHT_APPLE_DWI=m CONFIG_BACKLIGHT_QCOM_WLED=m CONFIG_BACKLIGHT_LP855X=m CONFIG_BACKLIGHT_GPIO=m CONFIG_LOGO=y -# CONFIG_LOGO_LINUX_MONO is not set -# CONFIG_LOGO_LINUX_VGA16 is not set CONFIG_SOUND=m CONFIG_SND=m CONFIG_SND_ALOOP=m @@ -1180,8 +1161,6 @@ CONFIG_SND_SOC_WSA884X=m CONFIG_SND_SOC_NAU8822=m CONFIG_SND_SOC_LPASS_WSA_MACRO=m CONFIG_SND_SOC_LPASS_VA_MACRO=m -CONFIG_SND_SOC_LPASS_RX_MACRO=m -CONFIG_SND_SOC_LPASS_TX_MACRO=m CONFIG_SND_SIMPLE_CARD=m CONFIG_SND_AUDIO_GRAPH_CARD=m CONFIG_SND_AUDIO_GRAPH_CARD2=m @@ -1209,8 +1188,8 @@ CONFIG_USB_ACM=m CONFIG_USB_STORAGE=y CONFIG_USB_CDNS_SUPPORT=m CONFIG_USB_CDNS3=m -CONFIG_USB_CDNS3_GADGET=y CONFIG_USB_CDNS3_HOST=y +CONFIG_USB_CDNS3_GADGET=y CONFIG_USB_MTU3=y CONFIG_USB_MUSB_HDRC=y CONFIG_USB_MUSB_SUNXI=y @@ -1311,7 +1290,6 @@ CONFIG_SCSI_UFS_RENESAS=m CONFIG_SCSI_UFS_TI_J721E=m CONFIG_SCSI_UFS_EXYNOS=y CONFIG_SCSI_UFS_ROCKCHIP=y -CONFIG_NEW_LEDS=y CONFIG_LEDS_CLASS=y CONFIG_LEDS_CLASS_FLASH=m CONFIG_LEDS_CLASS_MULTICOLOR=m @@ -1430,7 +1408,6 @@ CONFIG_EC_LENOVO_YOGA_C630=m CONFIG_EC_LENOVO_THINKPAD_T14S=m CONFIG_COMMON_CLK_APPLE_NCO=m CONFIG_COMMON_CLK_RK808=y -CONFIG_COMMON_CLK_SCMI=y CONFIG_COMMON_CLK_SCPI=y CONFIG_COMMON_CLK_CS2000_CP=y CONFIG_COMMON_CLK_FSL_SAI=y @@ -1450,18 +1427,6 @@ CONFIG_CLK_IMX8ULP=y CONFIG_CLK_IMX93=y CONFIG_CLK_IMX95_BLK_CTL=y CONFIG_TI_SCI_CLK=y -CONFIG_COMMON_CLK_MT8192_AUDSYS=y -CONFIG_COMMON_CLK_MT8192_CAMSYS=y -CONFIG_COMMON_CLK_MT8192_IMGSYS=y -CONFIG_COMMON_CLK_MT8192_IMP_IIC_WRAP=y -CONFIG_COMMON_CLK_MT8192_IPESYS=y -CONFIG_COMMON_CLK_MT8192_MDPSYS=y -CONFIG_COMMON_CLK_MT8192_MFGCFG=y -CONFIG_COMMON_CLK_MT8192_MMSYS=y -CONFIG_COMMON_CLK_MT8192_MSDC=y -CONFIG_COMMON_CLK_MT8192_SCP_ADSP=y -CONFIG_COMMON_CLK_MT8192_VDECSYS=y -CONFIG_COMMON_CLK_MT8192_VENCSYS=y CONFIG_COMMON_CLK_QCOM=y CONFIG_CLK_ELIZA_DISPCC=m CONFIG_CLK_ELIZA_GCC=y @@ -1670,7 +1635,6 @@ CONFIG_IMX_SCU_PD=y CONFIG_QCOM_CPR=y CONFIG_QCOM_RPMHPD=y CONFIG_QCOM_RPMPD=y -CONFIG_ROCKCHIP_PM_DOMAINS=y CONFIG_TI_SCI_PM_DOMAINS=y CONFIG_ARM_IMX_BUS_DEVFREQ=y CONFIG_ARM_IMX8M_DDRC_DEVFREQ=m @@ -1799,9 +1763,9 @@ CONFIG_PHY_SAMSUNG_UFS=y CONFIG_PHY_UNIPHIER_USB2=y CONFIG_PHY_UNIPHIER_USB3=y CONFIG_PHY_TEGRA_XUSB=y +CONFIG_OMAP_USB2=m CONFIG_PHY_AM654_SERDES=m CONFIG_PHY_J721E_WIZ=m -CONFIG_OMAP_USB2=m CONFIG_PHY_XILINX_ZYNQMP=m CONFIG_ARM_CCI_PMU=m CONFIG_ARM_CCN=m @@ -1852,10 +1816,7 @@ CONFIG_OPTEE=y CONFIG_QCOMTEE=m CONFIG_MUX_GPIO=m CONFIG_MUX_MMIO=y -CONFIG_SLIMBUS=m -CONFIG_SLIM_QCOM_CTRL=m CONFIG_SLIM_QCOM_NGD_CTRL=m -CONFIG_INTERCONNECT=y CONFIG_INTERCONNECT_IMX=y CONFIG_INTERCONNECT_IMX8MM=m CONFIG_INTERCONNECT_IMX8MN=m @@ -1914,14 +1875,12 @@ CONFIG_OVERLAY_FS=m CONFIG_VFAT_FS=y CONFIG_TMPFS_POSIX_ACL=y CONFIG_HUGETLBFS=y -CONFIG_CONFIGFS_FS=y CONFIG_EFIVAR_FS=y CONFIG_UBIFS_FS=m CONFIG_SQUASHFS=y CONFIG_PSTORE_RAM=m CONFIG_NFS_FS=y CONFIG_NFS_V4=y -CONFIG_NFS_V4_1=y CONFIG_NFS_V4_2=y CONFIG_ROOT_NFS=y CONFIG_9P_FS=m @@ -1932,11 +1891,8 @@ CONFIG_CRYPTO_USER=y CONFIG_CRYPTO_BENCHMARK=m CONFIG_CRYPTO_CHACHA20=m CONFIG_CRYPTO_ECHAINIV=y -CONFIG_CRYPTO_SHA3=m -CONFIG_CRYPTO_SM3=m CONFIG_CRYPTO_USER_API_RNG=m CONFIG_CRYPTO_GHASH_ARM64_CE=y -CONFIG_CRYPTO_AES_ARM64_CE_BLK=y CONFIG_CRYPTO_AES_ARM64_BS=m CONFIG_CRYPTO_AES_ARM64_CE_CCM=y CONFIG_CRYPTO_DEV_SUN8I_CE=m @@ -1960,8 +1916,6 @@ CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y CONFIG_DEBUG_INFO_REDUCED=y CONFIG_MAGIC_SYSRQ=y CONFIG_DEBUG_FS=y -# CONFIG_SCHED_DEBUG is not set -# CONFIG_DEBUG_PREEMPT is not set # CONFIG_FTRACE is not set CONFIG_CORESIGHT=m CONFIG_CORESIGHT_LINK_AND_SINK_TMC=m diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c index 96dbf04138be..43ae2121f01c 100644 --- a/drivers/i2c/busses/i2c-qcom-geni.c +++ b/drivers/i2c/busses/i2c-qcom-geni.c @@ -74,9 +74,12 @@ enum geni_i2c_err_code { #define PACKING_BYTES_PW 4 #define ABORT_TIMEOUT HZ -#define XFER_TIMEOUT HZ #define RST_TIMEOUT HZ +/* 9 bits per byte (8 data + 1 ACK), 10x safety margin, 300ms floor */ +#define I2C_TIMEOUT_SAFETY_COEFFICIENT 10 +#define I2C_TIMEOUT_MIN_USEC 300000 + struct geni_i2c_desc { bool no_dma_support; unsigned int tx_fifo_depth; @@ -204,6 +207,16 @@ static int geni_i2c_clk_map_idx(struct geni_i2c_dev *gi2c) return -EINVAL; } +static unsigned long geni_i2c_xfer_timeout(struct geni_i2c_dev *gi2c, size_t len) +{ + size_t bit_cnt = len * 9; + size_t bit_usec = (bit_cnt * USEC_PER_SEC) / gi2c->clk_freq_out; + size_t xfer_max_usec = (bit_usec * I2C_TIMEOUT_SAFETY_COEFFICIENT) + + I2C_TIMEOUT_MIN_USEC; + + return usecs_to_jiffies(xfer_max_usec); +} + static int qcom_geni_i2c_conf(struct geni_se *se, unsigned long freq) { struct geni_i2c_dev *gi2c = dev_get_drvdata(se->dev); @@ -471,7 +484,7 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg, } cur = gi2c->cur; - time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); + time_left = wait_for_completion_timeout(&gi2c->done, geni_i2c_xfer_timeout(gi2c, len)); if (!time_left) geni_i2c_abort_xfer(gi2c); @@ -513,7 +526,7 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg, writel_relaxed(1, se->base + SE_GENI_TX_WATERMARK_REG); cur = gi2c->cur; - time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); + time_left = wait_for_completion_timeout(&gi2c->done, geni_i2c_xfer_timeout(gi2c, len)); if (!time_left) geni_i2c_abort_xfer(gi2c); @@ -591,7 +604,7 @@ static void geni_i2c_gpi_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_ * geni_i2c_gpi_multi_xfer_timeout_handler() - Handles multi message transfer timeout * @dev: Pointer to the corresponding dev node * @multi_xfer: Pointer to the geni_i2c_gpi_multi_desc_xfer - * @transfer_timeout_msecs: Timeout value in milliseconds + * @transfer_timeout_msecs: Per-message completion timeout in jiffies * @transfer_comp: Completion object of the transfer * * This function waits for the completion of each processed transfer messages @@ -601,7 +614,7 @@ static void geni_i2c_gpi_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_ */ static int geni_i2c_gpi_multi_xfer_timeout_handler(struct device *dev, struct geni_i2c_gpi_multi_desc_xfer *multi_xfer, - u32 transfer_timeout_msecs, + unsigned long timeout_jiffies, struct completion *transfer_comp) { int i; @@ -612,7 +625,7 @@ static int geni_i2c_gpi_multi_xfer_timeout_handler(struct device *dev, if (multi_xfer->msg_idx_cnt != multi_xfer->irq_cnt) { time_left = wait_for_completion_timeout(transfer_comp, - transfer_timeout_msecs); + timeout_jiffies); if (!time_left) { dev_err(dev, "%s: Transfer timeout\n", __func__); return -ETIMEDOUT; @@ -736,8 +749,15 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], dma_async_issue_pending(gi2c->tx_c); if ((msg_idx == (gi2c->num_msgs - 1)) || flags & DMA_PREP_INTERRUPT) { + size_t max_len = 0; + int j; + + for (j = 0; j < gi2c->num_msgs; j++) + max_len = max_t(size_t, max_len, msgs[j].len); + ret = geni_i2c_gpi_multi_xfer_timeout_handler(gi2c->se.dev, gi2c_gpi_xfer, - XFER_TIMEOUT, &gi2c->done); + geni_i2c_xfer_timeout( + gi2c, max_len), &gi2c->done); if (ret) { dev_err(gi2c->se.dev, "I2C multi write msg transfer timeout: %d\n", @@ -852,7 +872,8 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i if (!gi2c->is_tx_multi_desc_xfer) { dma_async_issue_pending(gi2c->tx_c); - time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT); + time_left = wait_for_completion_timeout(&gi2c->done, geni_i2c_xfer_timeout( + gi2c, msgs[i].len)); if (!time_left) { dev_err(gi2c->se.dev, "%s:I2C timeout\n", __func__); gi2c->err = -ETIMEDOUT; -- 2.34.1

1 month, 2 weeks

What's Wave Rider game?

by Leo Enda

Wave Rider surprised me more than I expected. The game looks simple at first, but once the speed increases and the waves become unstable, every run starts feeling intense. Unlike many endless runner games that rely only on fast movement, Wave Rider creates pressure through unpredictable water physics and constantly changing obstacle patterns. Play Wave Rider online at https://wave-rider.io The gameplay is built around survival. Your board moves forward automatically while you focus on steering through dangerous sections of water. Floating barriers, underwater mines, sharp turns, and narrow lanes appear quickly, forcing players to react within seconds. What I liked most is how the game balances smooth surfing movement with sudden moments of chaos. Sometimes the water feels calm, then everything changes when multiple obstacles appear together. Wave Rider also rewards risky decisions. Pearls are often hidden near dangerous routes, making players choose between safe movement and higher scores. I found myself taking bigger risks after every run just to see how far I could push the distance counter. The durability system adds even more tension because repeated small crashes slowly reduce your chance of surviving longer sessions. Game Controls Left Arrow / A: Move left Right Arrow / D: Move right Spacebar or Up Arrow: Jump or glide over obstacles The controls are easy to learn, but mastering the timing takes practice. Quick reactions help, but smooth movement and patience usually lead to better runs. Players who panic and change direction too aggressively often crash faster than expected. Overall, Wave Rider feels like a solid arcade experience for anyone who enjoys reaction-based gameplay. The combination of flowing water, rising speed, and nonstop danger makes every session feel fresh and competitive.

1 month, 2 weeks

[PATCH v18 00/42] DEPT(DEPendency Tracker)

by Byungchul Park

I'm happy to see that DEPT reported real problems in practice: https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SA… https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.pa… https://lore.kernel.org/all/b6e00e77-4a8c-4e05-ab79-266bf05fcc2d@igalia.com/ I’ve added documentation describing DEPT — this should help you understand what DEPT is and how it works. You can use DEPT simply by enabling CONFIG_DEPT and checking dmesg at runtime. --- Hi Linus and folks, I’ve been developing a tool to detect deadlock possibilities by tracking waits/events — rather than lock acquisition order — to cover all the synchronization mechanisms. To summarize the design rationale, starting from the problem statement, through analysis, to the solution: CURRENT STATUS -------------- Lockdep tracks lock acquisition order to identify deadlock conditions. Additionally, it tracks IRQ state changes — via {en,dis}able — to detect cases where locks are acquired unintentionally during interrupt handling. PROBLEM ------- Waits and their associated events that are never reachable can eventually lead to deadlocks. However, since Lockdep focuses solely on lock acquisition order, it has inherent limitations when handling waits and events. Moreover, by tracking only lock acquisition order, Lockdep cannot properly handle read locks or cross-event scenarios — such as wait_for_completion() and complete() — making it increasingly inadequate as a general-purpose deadlock detection tool. SOLUTION -------- Once again, waits and their associated events that are never reachable can eventually lead to deadlocks. The new solution, DEPT, focuses directly on waits and events. DEPT monitors waits and events, and reports them when any become unreachable. DEPT provides: * Correct handling of read locks. * Support for general waits and events. * Continuous operation, even after multiple reports. * Simple, intuitive annotation APIs. There are still false positives, and some are already being worked on for suppression. Especially splitting the folio class into several appropriate classes e.g. block device mapping class and regular file mapping class, is currently under active development by me and Yeoreum Yun. Anyway, these efforts will need to continue for a while, as we’ve seen with lockdep over two decades. DEPT is tagged as EXPERIMENTAL in Kconfig — meaning it’s not yet suitable for use as an automation tool. However, for those who are interested in using DEPT to analyze complex synchronization patterns and extract dependency insights, DEPT would be a great tool for the purpose. Thanks for your support and contributions to: Harry Yoo <harry.yoo(a)oracle.com> Gwan-gyeong Mun <gwan-gyeong.mun(a)intel.com> Yunseong Kim <ysk(a)kzalloc.com> Yeoreum Yun <yeoreum.yun(a)arm.com> FAQ --- Q. Is this the first attempt to solve this problem? A. No. The cross-release feature (commit b09be676e0ff2) attempted to address it — as a Lockdep extension. It was merged, but quickly reverted, because: While it uncovered valuable hidden issues, it also introduced false positives. Since these false positives mask further real problems with Lockdep — and developers strongly dislike them — the feature was rolled back. Q. Why wasn’t DEPT built as a Lockdep extension? A. Lockdep is the result of years of work by kernel developers — and is now very stable. But I chose to build DEPT separately, because: While reusing BFS(Breadth First Search) and Lockdep’s hashing is beneficial, the rest of the system must be rebuilt from scratch to align with DEPT’s wait-event model — since Lockdep was originally designed for tracking lock acquisition orders, not wait-event dependencies. Q. Do you plan to replace Lockdep entirely? A. Not at all — Lockdep still plays a vital role in validating correct lock usage. While its dependency-checking logic should eventually be superseded by DEPT, the rest of its functionality should stay. Q. Should we replace the dependency check immediately? A. Absolutely not. Lockdep’s stability is the result of years of hard work by kernel developers. Lockdep and DEPT should run side by side until DEPT matures. Q. Stronger detection often leads to more false positives — which was a major pain point when cross-release was added. Is DEPT designed to handle this? A. Yes. DEPT’s simple, generalized design enables flexible reporting — so while false positives still need fixing, they’re far less disruptive than they were under the Lockdep extension, cross-release. Q. Why not fix all false positives out-of-tree before merging? A. Since the affected subsystems span the entire kernel, like Lockdep, which has relied on annotations to avoid false positives over the last two decades, DEPT too will require the annotation efforts. Performing annotation work within the mainline will help us add annotations more appropriately and will also make DEPT a useful tool for a wider range of users more quickly. CONFIG_DEPT is marked EXPERIMENTAL, so it’s opt-in. Some users are already interested in using DEPT to analyze complex synchronization patterns and extract dependency insights. Byungchul --- Changes from v17: 1. Rebase on the mainline as of 2025 Dec 5. 2. Convert the documents' format from txt to rst. (feedbacked by Jonathan Corbet and Bagas Sanjaya) 3. Move the documents from 'Documentation/dependency' to 'Documentation/dev-tools'. (feedbakced by Jonathan Corbet) 4. Improve the documentation. (feedbacked by NeilBrown) 5. Use a common function, enter_from_user_mode(), instead of arch specific code, to notice context switch from user mode. (feedbacked by Dave Hansen, Mark Rutland, and Mark Brown) 6. Resolve the header dependency issue by using dept's internal header, instead of relocating 'struct llist_{head,node}' to another header. (feedbacked by Greg KH) 7. Improve page(or folio) usage type APIs. 8. Add rust helper for wait_for_completion(). (feedbacked by Guangbo Cui, Boqun Feng, and Danilo Krummrich) 9. Refine some commit messages. Changes from v16: 1. Rebase on v6.17. 2. Fix a false positive from rcu (by Yunseong Kim) 3. Introduce APIs to set page's usage, dept_set_page_usage() and dept_reset_page_usage() to avoid false positives. 4. Consider lock_page() as a potential wait unconditionally. 5. Consider folio_lock_killable() as a potential wait unconditionally. 6. Add support for tracking PG_writeback waits and events. 7. Fix two build errors due to the additional debug information added by dept. (by Yunseong Kim) Changes from v15: 1. Fix typo and improve comments and commit messages (feedbacked by ALOK TIWARI, Waiman Long, and kernel test robot). 2. Do not stop dept on detection of cicular dependency of recover event, allowing to keep reporting. 3. Add SK hynix to copyright. 4. Consider folio_lock() as a potential wait unconditionally. 5. Fix Kconfig dependency bug (feedbacked by kernel test rebot). 6. Do not suppress reports that involve classes even that have already involved in other reports, allowing to keep reporting. Changes from v14: 1. Rebase on the current latest, v6.15-rc6. 2. Refactor dept code. 3. With multi event sites for a single wait, even if an event forms a circular dependency, the event can be recovered by other event(or wake up) paths. Even though informing the circular dependency is worthy but it should be suppressed once informing it, if it doesn't lead an actual deadlock. So introduce APIs to annotate the relationship between event site and recover site, that are, event_site() and dept_recover_event(). 4. wait_for_completion() worked with dept map embedded in struct completion. However, it generates a few false positves since all the waits using the instance of struct completion, share the map and key. To avoid the false positves, make it not to share the map and key but each wait_for_completion() caller have its own key by default. Of course, external maps also can be used if needed. 5. Fix a bug about hardirq on/off tracing. 6. Implement basic unit test for dept. 7. Add more supports for dma fence synchronization. 8. Add emergency stop of dept e.g. on panic(). 9. Fix false positives by mmu_notifier_invalidate_*(). 10. Fix recursive call bug by DEPT_WARN_*() and DEPT_STOP(). 11. Fix trivial bugs in DEPT_WARN_*() and DEPT_STOP(). 12. Fix a bug that a spin lock, dept_pool_spin, is used in both contexts of irq disabled and enabled without irq disabled. 13. Suppress reports with classes, any of that already have been reported, even though they have different chains but being barely meaningful. 14. Print stacktrace of the wait that an event is now waking up, not only stacktrace of the event. 15. Make dept aware of lockdep_cmp_fn() that is used to avoid false positives in lockdep so that dept can also avoid them. 16. Do do_event() only if there are no ecxts have been delimited. 17. Fix a bug that was not synchronized for stage_m in struct dept_task, using a spin lock, dept_task()->stage_lock. 18. Fix a bug that dept didn't handle the case that multiple ttwus for a single waiter can be called at the same time e.i. a race issue. 19. Distinguish each kernel context from others, not only by system call but also by user oriented fault so that dept can work with more accuracy information about kernel context. That helps to avoid a few false positives. 20. Limit dept's working to x86_64 and arm64. Changes from v13: 1. Rebase on the current latest version, v6.9-rc7. 2. Add 'dept' documentation describing dept APIs. Changes from v12: 1. Refine the whole document for dept. 2. Add 'Interpret dept report' section in the document, using a deadlock report obtained in practice. Hope this version of document helps guys understand dept better. https://lore.kernel.org/lkml/6383cde5-cf4b-facf-6e07-1378a485657d@I-love.SA… https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.pa… Changes from v11: 1. Add 'dept' documentation describing the concept of dept. 2. Rewrite the commit messages of the following commits for using weaker lockdep annotation, for better description. fs/jbd2: Use a weaker annotation in journal handling cpu/hotplug: Use a weaker annotation in AP thread (feedbacked by Thomas Gleixner) Changes from v10: 1. Fix noinstr warning when building kernel source. 2. dept has been reporting some false positives due to the folio lock's unfairness. Reflect it and make dept work based on dept annotaions instead of just wait and wake up primitives. 3. Remove the support for PG_writeback while working on 2. I will add the support later if needed. 4. dept didn't print stacktrace for [S] if the participant of a deadlock is not lock mechanism but general wait and event. However, it made hard to interpret the report in that case. So add support to print stacktrace of the requestor who asked the event context to run - usually a waiter of the event does it just before going to wait state. 5. Give up tracking raw_local_irq_{disable,enable}() since it totally messed up dept's irq tracking. So make it work in the same way as lockdep does. I will consider it once any false positives by those are observed again. 6. Change the manual rwsem_acquire_read(->j_trans_commit_map) annotation in fs/jbd2/transaction.c to the try version so that it works as much as it exactly needs. 7. Remove unnecessary 'inline' keyword in dept.c and add '__maybe_unused' to a needed place. Changes from v9: 1. Fix a bug. SDT tracking didn't work well because of my big mistake that I should've used waiter's map to indentify its class but it had been working with waker's one. FYI, PG_locked and PG_writeback weren't affected. They still worked well. (reported by YoungJun) Changes from v8: 1. Fix build error by adding EXPORT_SYMBOL(PG_locked_map) and EXPORT_SYMBOL(PG_writeback_map) for kernel module build - appologize for that. (reported by kernel test robot) 2. Fix build error by removing header file's circular dependency that was caused by "atomic.h", "kernel.h" and "irqflags.h", which I introduced - appolgize for that. (reported by kernel test robot) Changes from v7: 1. Fix a bug that cannot track rwlock dependency properly, introduced in v7. (reported by Boqun and lockdep selftest) 2. Track wait/event of PG_{locked,writeback} more aggressively assuming that when a bit of PG_{locked,writeback} is cleared there might be waits on the bit. (reported by Linus, Hillf and syzbot) 3. Fix and clean bad style code e.i. unnecessarily introduced a randome pattern and so on. (pointed out by Linux) 4. Clean code for applying dept to wait_for_completion(). Changes from v6: 1. Tie to task scheduler code to track sleep and try_to_wake_up() assuming sleeps cause waits, try_to_wake_up()s would be the events that those are waiting for, of course with proper dept annotations, sdt_might_sleep_weak(), sdt_might_sleep_strong() and so on. For these cases, class is classified at sleep entrance rather than the synchronization initialization code. Which would extremely reduce false alarms. 2. Remove the dept associated instance in each page struct for tracking dependencies by PG_locked and PG_writeback thanks to the 1. work above. 3. Introduce CONFIG_dept_AGGRESIVE_TIMEOUT_WAIT to suppress reports that waits with timeout set are involved, for those who don't like verbose reporting. 4. Add a mechanism to refill the internal memory pools on running out so that dept could keep working as long as free memory is available in the system. 5. Re-enable tracking hashed-waitqueue wait. That's going to no longer generate false positives because class is classified at sleep entrance rather than the waitqueue initailization. 6. Refactor to make it easier to port onto each new version of the kernel. 7. Apply dept to dma fence. 8. Do trivial optimizaitions. Changes from v5: 1. Use just pr_warn_once() rather than WARN_ONCE() on the lack of internal resources because WARN_*() printing stacktrace is too much for informing the lack. (feedback from Ted, Hyeonggon) 2. Fix trivial bugs like missing initializing a struct before using it. 3. Assign a different class per task when handling onstack variables for waitqueue or the like. Which makes dept distinguish between onstack variables of different tasks so as to prevent false positives. (reported by Hyeonggon) 4. Make dept aware of even raw_local_irq_*() to prevent false positives. (reported by Hyeonggon) 5. Don't consider dependencies between the events that might be triggered within __schedule() and the waits that requires __schedule(), real ones. (reported by Hyeonggon) 6. Unstage the staged wait that has prepare_to_wait_event()'ed *and* yet to get to __schedule(), if we encounter __schedule() in-between for another sleep, which is possible if e.g. a mutex_lock() exists in 'condition' of ___wait_event(). 7. Turn on CONFIG_PROVE_LOCKING when CONFIG_DEPT is on, to rely on the hardirq and softirq entrance tracing to make dept more portable for now. Changes from v4: 1. Fix some bugs that produce false alarms. 2. Distinguish each syscall context from another *for arm64*. 3. Make it not warn it but just print it in case dept ring buffer gets exhausted. (feedback from Hyeonggon) 4. Explicitely describe "EXPERIMENTAL" and "dept might produce false positive reports" in Kconfig. (feedback from Ted) Changes from v3: 1. dept shouldn't create dependencies between different depths of a class that were indicated by *_lock_nested(). dept normally doesn't but it does once another lock class comes in. So fixed it. (feedback from Hyeonggon) 2. dept considered a wait as a real wait once getting to __schedule() even if it has been set to TASK_RUNNING by wake up sources in advance. Fixed it so that dept doesn't consider the case as a real wait. (feedback from Jan Kara) 3. Stop tracking dependencies with a map once the event associated with the map has been handled. dept will start to work with the map again, on the next sleep. Changes from v2: 1. Disable dept on bit_wait_table[] in sched/wait_bit.c reporting a lot of false positives, which is my fault. Wait/event for bit_wait_table[] should've been tagged in a higher layer for better work, which is a future work. (feedback from Jan Kara) 2. Disable dept on crypto_larval's completion to prevent a false positive. Changes from v1: 1. Fix coding style and typo. (feedback from Steven) 2. Distinguish each work context from another in workqueue. 3. Skip checking lock acquisition with nest_lock, which is about correct lock usage that should be checked by lockdep. Changes from RFC(v0): 1. Prevent adding a wait tag at prepare_to_wait() but __schedule(). (feedback from Linus and Matthew) 2. Use try version at lockdep_acquire_cpus_lock() annotation. 3. Distinguish each syscall context from another. Byungchul Park (41): dept: implement DEPT(DEPendency Tracker) dept: add single event dependency tracker APIs dept: add lock dependency tracker APIs dept: tie to lockdep and IRQ tracing dept: add proc knobs to show stats and dependency graph dept: distinguish each kernel context from another dept: distinguish each work from another dept: add a mechanism to refill the internal memory pools on running out dept: record the latest one out of consecutive waits of the same class dept: apply sdt_might_sleep_{start,end}() to wait_for_completion()/complete() dept: apply sdt_might_sleep_{start,end}() to swait dept: apply sdt_might_sleep_{start,end}() to waitqueue wait dept: apply sdt_might_sleep_{start,end}() to hashed-waitqueue wait dept: apply sdt_might_sleep_{start,end}() to dma fence dept: track timeout waits separately with a new Kconfig dept: apply timeout consideration to wait_for_completion()/complete() dept: apply timeout consideration to swait dept: apply timeout consideration to waitqueue wait dept: apply timeout consideration to hashed-waitqueue wait dept: apply timeout consideration to dma fence wait dept: make dept able to work with an external wgen dept: track PG_locked with dept dept: print staged wait's stacktrace on report locking/lockdep: prevent various lockdep assertions when lockdep_off()'ed dept: add documents for dept cpu/hotplug: use a weaker annotation in AP thread dept: assign dept map to mmu notifier invalidation synchronization dept: assign unique dept_key to each distinct dma fence caller dept: make dept aware of lockdep_set_lock_cmp_fn() annotation dept: make dept stop from working on debug_locks_off() dept: assign unique dept_key to each distinct wait_for_completion() caller completion, dept: introduce init_completion_dmap() API dept: introduce a new type of dependency tracking between multi event sites dept: add module support for struct dept_event_site and dept_event_site_dep dept: introduce event_site() to disable event tracking if it's recoverable dept: implement a basic unit test for dept dept: call dept_hardirqs_off() in local_irq_*() regardless of irq state dept: introduce APIs to set page usage and use subclasses_evt for the usage dept: track PG_writeback with dept SUNRPC: relocate struct rcu_head to the first field of struct rpc_xprt mm: percpu: increase PERCPU_DYNAMIC_SIZE_SHIFT on DEPT and large PAGE_SIZE Yunseong Kim (1): rcu/update: fix same dept key collision between various types of RCU Documentation/dev-tools/dept.rst | 778 ++++++ Documentation/dev-tools/dept_api.rst | 125 + drivers/dma-buf/dma-fence.c | 23 +- include/asm-generic/vmlinux.lds.h | 13 +- include/linux/completion.h | 124 +- include/linux/dept.h | 402 +++ include/linux/dept_ldt.h | 78 + include/linux/dept_sdt.h | 68 + include/linux/dept_unit_test.h | 67 + include/linux/dma-fence.h | 74 +- include/linux/hardirq.h | 3 + include/linux/irq-entry-common.h | 4 + include/linux/irqflags.h | 21 +- include/linux/local_lock_internal.h | 1 + include/linux/lockdep.h | 105 +- include/linux/lockdep_types.h | 3 + include/linux/mm_types.h | 4 + include/linux/mmu_notifier.h | 26 + include/linux/module.h | 5 + include/linux/mutex.h | 1 + include/linux/page-flags.h | 217 +- include/linux/pagemap.h | 37 +- include/linux/percpu-rwsem.h | 2 +- include/linux/percpu.h | 4 + include/linux/rcupdate_wait.h | 13 +- include/linux/rtmutex.h | 1 + include/linux/rwlock_types.h | 1 + include/linux/rwsem.h | 1 + include/linux/sched.h | 118 + include/linux/seqlock.h | 2 +- include/linux/spinlock_types_raw.h | 3 + include/linux/srcu.h | 2 +- include/linux/sunrpc/xprt.h | 9 +- include/linux/swait.h | 3 + include/linux/wait.h | 3 + include/linux/wait_bit.h | 3 + init/init_task.c | 2 + init/main.c | 2 + kernel/Makefile | 1 + kernel/cpu.c | 2 +- kernel/dependency/Makefile | 5 + kernel/dependency/dept.c | 3499 ++++++++++++++++++++++++++ kernel/dependency/dept_hash.h | 10 + kernel/dependency/dept_internal.h | 314 +++ kernel/dependency/dept_object.h | 13 + kernel/dependency/dept_proc.c | 94 + kernel/dependency/dept_unit_test.c | 173 ++ kernel/exit.c | 1 + kernel/fork.c | 2 + kernel/locking/lockdep.c | 33 + kernel/module/main.c | 19 + kernel/rcu/rcu.h | 1 + kernel/rcu/update.c | 5 +- kernel/sched/completion.c | 62 +- kernel/sched/core.c | 9 + kernel/workqueue.c | 3 + lib/Kconfig.debug | 48 + lib/debug_locks.c | 2 + lib/locking-selftest.c | 2 + mm/filemap.c | 38 + mm/mm_init.c | 3 + mm/mmu_notifier.c | 31 +- rust/helpers/completion.c | 5 + 63 files changed, 6602 insertions(+), 121 deletions(-) create mode 100644 Documentation/dev-tools/dept.rst create mode 100644 Documentation/dev-tools/dept_api.rst create mode 100644 include/linux/dept.h create mode 100644 include/linux/dept_ldt.h create mode 100644 include/linux/dept_sdt.h create mode 100644 include/linux/dept_unit_test.h create mode 100644 kernel/dependency/Makefile create mode 100644 kernel/dependency/dept.c create mode 100644 kernel/dependency/dept_hash.h create mode 100644 kernel/dependency/dept_internal.h create mode 100644 kernel/dependency/dept_object.h create mode 100644 kernel/dependency/dept_proc.c create mode 100644 kernel/dependency/dept_unit_test.c base-commit: 43dfc13ca972988e620a6edb72956981b75ab6b0 -- 2.17.1

1 month, 2 weeks

Re: Unlocking Wordplay: A Guide to the Connections Game

by one slopalice

You only plan to cross one more road. Then another train appears, a river blocks your path, and somehow twenty minutes disappear. Crossy Road has a habit of turning tiny victories into "just one more try" moments because every run feels close enough to beat your previous score. What Makes This Game Different Unlike many endless runners that focus on pure speed, Crossy Road is built around timing and quick decisions. Every step changes the situation. Cars follow different patterns, trains arrive with almost no warning, and rivers force you to think ahead instead of simply reacting. The randomly generated maps keep familiar mechanics feeling fresh, while dozens of unlockable characters add personality without changing the core challenge. After enough runs, you stop chasing distance alone and start reading traffic patterns, planning safe routes, and knowing when waiting for a second is smarter than rushing forward. Check out https://crossyroad2.io now.

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