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2661 discussions

Re: [PATCH] coresight: syscfg: fix deadlock on device registration failure

by Leo Yan

On Tue, Aug 25, 2026 at 09:47:17AM +0800, yingchao wrote: > diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c > index 2bfdd7b45e49..d0e7e4720e46 100644 > --- a/drivers/hwtracing/coresight/coresight-syscfg.c > +++ b/drivers/hwtracing/coresight/coresight-syscfg.c > @@ -1210,8 +1210,14 @@ static int cscfg_create_device(void) > dev->init_name = "cs_system_cfg"; > > err = device_register(dev); > - if (err) > + if (err) { > + /* put_device() triggers cscfg_dev_release() which takes > + * cscfg_mutex, so drop the lock first to avoid deadlocking. > + */ > + mutex_unlock(&cscfg_mutex); > put_device(dev); > + return err; > + } As module init and exit are serialized by the kernel, I don't think we need the mutex to protect the allocation and freeing of cscfg_mgr. The mutex should only be used for exclusively access cscfg_mgr. So how about the change below? ---8<--- diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index 2bfdd7b45e49..2dd0b29f44e4 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -1173,27 +1173,21 @@ struct device *cscfg_device(void) /* Must have a release function or the kernel will complain on module unload */ static void cscfg_dev_release(struct device *dev) { - mutex_lock(&cscfg_mutex); kfree(cscfg_mgr); cscfg_mgr = NULL; - mutex_unlock(&cscfg_mutex); } /* a device is needed to "own" some kernel elements such as sysfs entries. */ static int cscfg_create_device(void) { struct device *dev; - int err = -ENOMEM; - - mutex_lock(&cscfg_mutex); - if (cscfg_mgr) { - err = -EINVAL; - goto create_dev_exit_unlock; - } + int err; cscfg_mgr = kzalloc_obj(struct cscfg_manager); if (!cscfg_mgr) - goto create_dev_exit_unlock; + return -ENOMEM; + + mutex_lock(&cscfg_mutex); /* initialise the cscfg_mgr structure */ INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list); @@ -1204,6 +1198,8 @@ static int cscfg_create_device(void) cscfg_mgr->load_state = CSCFG_NONE; raw_spin_lock_init(&cscfg_mgr->sysfs_store_lock); + mutex_unlock(&cscfg_mutex); + /* setup the device */ dev = cscfg_device(); dev->release = cscfg_dev_release; @@ -1213,8 +1209,6 @@ static int cscfg_create_device(void) if (err) put_device(dev); -create_dev_exit_unlock: - mutex_unlock(&cscfg_mutex); return err; }

4 weeks

Re: [PATCH] coresight: fix typos in comments

by Leo Yan

On Fri, Sep 04, 2026 at 04:40:51PM +0530, Hemanth Selam wrote: > Fix typos in comments, reported by scripts/checkpatch.pl using the > misspelling list in scripts/spelling.txt. Only touches comments, no code > changes. > > Assisted-by: Cursor:claude-opus-5 > Signed-off-by: Hemanth Selam <hemanth.selam(a)gmail.com> Reviewed-by: Leo Yan <leo.yan(a)arm.com>

1 month

Re: [PATCH] docs: fix typos in Documentation/ABI/testing/sysfs-bus-coresight-devices-etm3x

by Leo Yan

On Fri, Sep 04, 2026 at 09:49:42AM +0530, tspamiitesh(a)gmail.com wrote: [...] > -Description: (RW) Enable/disable tracing on this specific trace entiry. > +Description: (RW) Enable/disable tracing on this specific trace entry. > Enabling a source implies the source has been configured > - properly and a sink has been identidifed for it. The path > + properly and a sink has been indentified for it. The path s/indentified/identified ?

1 month

Re: [PATCH v2] coresight: tnoc: fix trace ID path assignment failure on non-AMBA tnoc

by Leo Yan

On Wed, Sep 02, 2026 at 05:41:43PM +0800, Jie Gan wrote: > For a tnoc device not on the AMBA bus, atid was set to -EOPNOTSUPP. > trace_noc_id() returns this value directly to > coresight_path_assign_trace_id(), which only treats a literal 0 > return as "this device has no ID, keep searching the path" - > any other value is checked against IS_VALID_CS_TRACE_ID() and > rejected. A negative atid therefore made path assignment fail with > -EINVAL instead of falling through to the next device in the path > that could supply a valid trace ID. > > Use 0, the same sentinel coresight_path_assign_trace_id() already > recognizes as "not allocated", instead of -EOPNOTSUPP. > > Fixes: 5799dee92dc2 ("coresight-tnoc: add platform driver to support Interconnect TNOC") > Signed-off-by: Jie Gan <jie.gan(a)oss.qualcomm.com> Reviewed-by: Leo Yan <leo.yan(a)arm.com>

1 month

Re: [PATCH] coresight: fix trace ID search skipping pass-through NoC devices

by Leo Yan

On Wed, Sep 02, 2026 at 04:35:11PM +0800, Jie Gan wrote: [...] > Hi Leo, > > Thanks for the suggestion. You're welcome! > I will fix this in the TNOC driver. I agree that there is no need to use > additional error codes to report the failure. > > I will post the new fix patch after below patch[1] to be applied to avoid > conflict. The patch in the link has no fix tag, but current patch is a simple fix. I'd suggest to give priority this patch - this is friendly for porting to stable kernels. If there have dependency (based on your local test), you could explictly mention the dependency in cover letter and resend the tnoc probe series. Thanks, Leo > [1] https://lore.kernel.org/all/20260710-fix-tracenoc-probe-issue-v6-2-41eb36fe…

1 month

Re: [PATCH] coresight: fix trace ID search skipping pass-through NoC devices

by Leo Yan

Hi Jie, On Mon, Aug 17, 2026 at 04:50:15PM +0800, Jie Gan wrote: [...] > @@ -953,8 +953,12 @@ int coresight_path_assign_trace_id(struct coresight_path *path, > /* Assign a trace ID to the path for the first device that wants to do it */ > trace_id = coresight_get_trace_id(nd->csdev, mode, sink); > > - /* 0 means the device has no ID assignment, so keep searching */ > - if (trace_id == 0) > + /* > + * 0 means the device has no ID assignment, and -EOPNOTSUPP > + * means the device explicitly declines to assign one (e.g. a > + * pass-through NoC) - in both cases keep searching downstream. > + */ > + if (trace_id == 0 || trace_id == -EOPNOTSUPP) > continue; Based on IS_VALID_CS_TRACE_ID(), I see 0 is for no ID assignment, could you improve a bit tnoc.c instead? If so, We don't need to add a new error for the same purpose. ---8<--- diff --git a/drivers/hwtracing/coresight/coresight-tnoc.c b/drivers/hwtracing/coresight/coresight-tnoc.c index 9e8de4323d28..bf221c1e5c48 100644 --- a/drivers/hwtracing/coresight/coresight-tnoc.c +++ b/drivers/hwtracing/coresight/coresight-tnoc.c @@ -51,8 +51,8 @@ static void trace_noc_enable_hw(struct trace_noc_drvdata *drvdata) { u32 val; - /* No valid ATID, simply enable the unit */ - if (drvdata->atid == -EOPNOTSUPP) { + /* 0 means no ID assignment, simply enable the unit */ + if (!drvdata->atid) { writel(TRACE_NOC_CTRL_PORTEN, drvdata->base + TRACE_NOC_CTRL); return; } @@ -130,10 +130,8 @@ static int trace_noc_init_default_data(struct trace_noc_drvdata *drvdata) { int atid; - if (!dev_is_amba(drvdata->dev)) { - drvdata->atid = -EOPNOTSUPP; + if (!dev_is_amba(drvdata->dev)) return 0; - } atid = coresight_trace_id_get_system_id(); if (atid < 0)

1 month

Re: [PATCH 2/2] perf: arm_spe: Prefer large AUX mappings

by Leo Yan

On Mon, Aug 10, 2026 at 04:10:48PM +0100, Will Deacon wrote: > On Mon, Aug 10, 2026 at 03:44:42PM +0100, Leo Yan wrote: > > Commit 18049c8cff9c ("perf/aux: Allocate non-contiguous AUX pages by > > default") made the AUX allocator use order-0 pages by default unless a > > PMU explicitly asks for contiguous allocations. > > But that commit specifically calls out SPE as benefitting from > non-contiguous pages: > > "For instance, ARM SPE and TRBE operate with virtual pages, and > Coresight ETR allocates a separate buffer. For these PMUs, > allocating contiguous AUX pages unnecessarily exacerbates memory > fragmentation. This fragmentation can prevent their use on > long-running devices." > > so why doesn't passing PERF_PMU_CAP_AUX_PREFER_LARGE reintroduce the > problems that 18049c8cff9c was trying to solve? The question is how "allocating contiguous AUX pages unnecessarily exacerbates memory fragmentation." The relevant information I could find is [1]: "On Android, we collect ETM data periodically on internal user devices for AutoFDO optimization (for both userspace libraries and the kernel). Allocating a large chunk of contiguous AUX pages (4M for each CPU) periodically is almost unbearable. The kernel may need to kill many processes to fulfill the request. It affects user experience even after using PMU." We might have missed chance to clarify how the fragmentation issue occurs in the first place. Let's say, a phone with 8 CPUs, allocating 4MB per CPU requires 32MB in total, which is a relatively small portion of 4GiB or 8GiB of RAM commonly found in phones. Moreover, once contiguous pages are freed, the buddy allocator can coalesce them again into buddy list. It is not obvious to me that PREFER_LARGE directly causes fragmentation. One case where AUX allocation could exacerbate fragmentation is when the system is already fragmented. If a high-order allocation fails and the allocator falls back to smaller-order blocks, those allocations may consume free blocks scattered across different buddy regions and make subsequent high-order allocations more difficult. If this is the main concern, I'd suggest using a smaller AUX buffer (e.g. 1MB or even 512KB) for TRBE/SPE to reduce memory pressure. Snapshot mode '-S' could also be considered, as it allows the buffer to be allocated once and reused for subsequent recordings by signals. OTOH, using only order-0 pages can significantly increase TTW overhead on the trace path and lead to overflows, we observe this causes huge trace discontinuity. In the end, we need to trace-off the fragmentation concern against the trace discontinuity. Thanks, Leo [1] https://lore.kernel.org/lkml/CALJ9ZPNLgEBxOmDim-vztUknEETwdL-Z2gJ8K9s44TiPg…

1 month

Re: [PATCH v4] coresight: coresight.h: add '*' to kernel-doc lines

by Leo Yan

On Sun, Aug 30, 2026 at 08:09:12PM -0700, Randy Dunlap wrote: > kernel-doc reports 2 (kernel-doc) lines in coresight.h that don't have > a beginning '*' in them, so fix these lines. > > Also convert struct coresight_trace_id_map to kernel-doc format to > remove another warning. > > Warning: include/linux/coresight.h:173 bad line: > connected to @src_port. NULL until the device is created > Warning: include/linux/coresight.h:177 bad line: > needs to be filtered. > Warning: include/linux/coresight.h:236 This comment starts with '/**', > but isn't a kernel-doc comment. > > Fixes: ec9903d6cc34 ("coresight: Add support for trace filtering by source") > Fixes: d49c9cf15f89 ("coresight: Rename connection members to make the direction explicit") > Signed-off-by: Randy Dunlap <rdunlap(a)infradead.org> Reviewed-by: Leo Yan <leo.yan(a)arm.com>

1 month

[PATCH v2 00/14] perf cs-etm: Per-thread mode fixes and snapshot wrap support

by James Clark

Fix a few issues with per-thread mode: - With TRBE, thread migrations hit a queue without a decoder assert - On nVHE, everything looks like guest trace instead of host - Tracing multiple threads didn't really work After adding a tests for those, it turns out there were some snapshot bugs not picked up by the other snapshot tests. That showed that the different snapshot searches for Intel BTS and Arm SPE were inconsistent and I think all tracers can benefit from using the same pointer fixup logic, so that gets refactored into the common auxtrace.c. Then SPE can just share the Intel BTS search as it was obviously copied from it originally. IntelPT keeps the more advanced duplicate data search, but in the future that could probably be made the common one and all tracers would benefit from using it (except maybe BTS if it always has a very small buffer, but I doubt the overhead of the duplicate search would be an issue). For now this is more of a refactor rather than behavioral change so don't do that yet. Signed-off-by: James Clark <james.clark(a)linaro.org> --- Changes in v2: - Remove stale "may be reset to -1 in per-thread mode" comment - Set CPU when queueing auxtrace fragments otherwise auxtrace_queues__add_event() overwrites the queue's CPU - Link to v1: https://patch.msgid.link/20260811-james-cs-unformatted-per-thread-fix-v1-0-… --- James Clark (14): perf cs-etm: Fix nVHE per-thread decoding perf cs-etm: Warn for invalid timestamp option perf cs-etm: Turn on context packet timestamps in per-thread mode perf cs-etm: Use per-CPU queues for per-thread mode perf cs-etm: Increase default timestamp generation period perf auxtrace: Turn Intel BTS snapshot search into a generic one perf arm-spe: Use generic snapshot search perf auxtrace: intel-pt: Use new snapshot_has_wrapped callback perf cs-etm: Queue partial AUX records perf cs-etm: Don't print missing buffers in snapshot mode perf auxtrace: cs-etm: Capture wrapped snapshots perf test: Allow infinite named_thread loops perf test: Add test for per-thread mode perf cs-etm: Test multiple per-thread threads Documentation/userspace-api/perf_ring_buffer.rst | 6 +- tools/perf/Documentation/perf-test.txt | 2 +- tools/perf/arch/arm/util/cs-etm.c | 30 ++++- tools/perf/arch/arm64/util/arm-spe.c | 147 +-------------------- tools/perf/arch/x86/util/intel-bts.c | 115 +--------------- tools/perf/arch/x86/util/intel-pt.c | 58 +++----- .../perf/tests/shell/coresight/per-thread-multi.sh | 78 +++++++++++ tools/perf/tests/shell/coresight/per-thread.sh | 48 +++++++ .../perf/tests/shell/coresight/raw_dump_stress.sh | 5 - tools/perf/tests/workloads/named_threads.c | 7 +- tools/perf/util/auxtrace.c | 136 +++++++++++++++++-- tools/perf/util/auxtrace.h | 20 ++- tools/perf/util/cs-etm.c | 101 ++++++++++---- 13 files changed, 384 insertions(+), 369 deletions(-) --- base-commit: 9453bc6a69ef43755f1c28d5688cacdd69fa16bd change-id: 20260605-james-cs-unformatted-per-thread-fix-50e723aa7f0e Best regards, -- James Clark <james.clark(a)linaro.org>

1 month, 1 week

[PATCH v9 00/13] fix several inconsistencies with sysfs configuration in etmX

by Yeoreum Yun

The current ETMx configuration via sysfs can lead to the following inconsistencies: - If a configuration is modified via sysfs while a perf session is active, the running configuration may differ between before a sched-out and after a subsequent sched-in. - If a perf session and sysfs session tries to enable concurrently, configuration from configfs could be corrupted (etm4). - There is chance to corrupt drvdata->config if perf session tries to enabled among handling cscfg_csdev_disable_active_config() in etm4_disable_sysfs() (etm4). To resolve these inconsistencies, the configuration should be separated into: - active_config, which is applied configuration for the current session - config, which stores the settings configured via sysfs. and apply configuration from configfs after taking a mode. Also, This patch set includes some small fixes: - missing trace id release in etm4x. - underflow issue for nrseqstate. - wrong check in etm4x_sspcicrn_present(). - missing call of cscfg_csdev_disable_active_config() This patch based on coresight tree's next Patch History ============= from v8 to v9: - add feat_csdev_lock guard interface. - set feat_csdev->drv_spinlock as NULL for etmv4_drvdata. - https://lore.kernel.org/all/20260629090007.1718746-1-yeoreum.yun@arm.com/ from v7 to v8: - accept @Leo Yan' suggestion to handle error. - small minor fixes following @Suzuki' suggestion. - https://lore.kernel.org/all/20260519154812.254884-1-yeoreum.yun@arm.com/ from v6 to v7: - rebase on coresight/next - add ETM_MAX_SEQ_TRANSITIONS define - remove redundant patch relavent cpu-hotplug as coresight-pm patch merged. - https://lore.kernel.org/all/20260422132203.977549-1-yeoreum.yun@arm.com/ from v5 to v6: - fix missing of calling cscfg_csdev_disable_active_config() - add rb & fixes tags. - add ss_status field in etm4x_drvdata to expose STATUS and PENDING bits. - https://lore.kernel.org/all/20260415165528.3369607-1-yeoreum.yun@arm.com/ from v4 to v5: - add rb-tag. - fix underflow issue for nrseqstate. - fix wrong check in etm4_sspcicrn_present(). - remove redundant fields on etmv4_save_state. - rename caps->ss_status to ss_cmp. - fix wrong location of etm4_release_trace_id. - https://lore.kernel.org/all/20260413142003.3549310-1-yeoreum.yun@arm.com/ from v3 to v4: - change etm_drvdata->spinlock type to raw_spin_lock_t - remove redundant call etmX_enable_hw() with starting_cpu() callsback. - fix missing trace id release. - add missing docs. - https://lore.kernel.org/all/20260412175506.412301-1-yeoreum.yun@arm.com/ from v2 to v3: - fix build error for etm3x. - fix checkpatch warning. - https://lore.kernel.org/all/20260410074310.2693385-1-yeoreum.yun@arm.com/ from v1 to v2 - rebased to v7.0-rc7. - introduce etmX_caps structure to save etmX's capabilities. - remove ss_status from etmv4_config. - modify active_config after taking a mode (perf/sysfs). - https://lore.kernel.org/all/20260317181705.2456271-1-yeoreum.yun@arm.com/ Yeoreum Yun (13): coresight: etm4x: fix wrong check of etm4x_sspcicrn_present() coresight: etm4x: fix underflow for usage of (nrseqstate - 1) coresight: etm4x: fix leaked trace id coresight: etm4x: fix inconsistencies with sysfs configuration coresight: etm4x: missing cscfg_csdev_disable_active_config() in perf enable coresight: etm3x: fix inconsistencies with sysfs configuration coresight: etm3x: change drvdata->spinlock type to raw_spin_lock_t coresight: etm3x: remove redundant cpu online check on etm_enable_sysfs() coresight: etm4x: introduce struct etm4_caps coresight: etm4x: exclude ss_status from drvdata->config coresight: etm4x: remove s_ex_level from config coresight: etm4x: remove redundant fields in etmv4_save_state coresight: etm3x: introduce struct etm_caps .../hwtracing/coresight/coresight-config.c | 18 +- .../hwtracing/coresight/coresight-config.h | 26 + drivers/hwtracing/coresight/coresight-etm.h | 48 +- .../coresight/coresight-etm3x-core.c | 96 ++-- .../coresight/coresight-etm3x-sysfs.c | 159 +++--- .../hwtracing/coresight/coresight-etm4x-cfg.c | 16 +- .../coresight/coresight-etm4x-core.c | 454 ++++++++++-------- .../coresight/coresight-etm4x-sysfs.c | 204 ++++---- drivers/hwtracing/coresight/coresight-etm4x.h | 204 ++++---- 9 files changed, 682 insertions(+), 543 deletions(-) base-commit: 98495b5a4d77dd22e106f462b76e1093a55b29a7 -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}

1 month, 1 week

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