Linaro-mm-sig

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14 participants
3706 discussions

[PATCH] dma-buf: Wait on the reservation object when sync'ing before CPU access

by Chris Wilson

Rendering operations to the dma-buf are tracked implicitly via the reservation_object (dmabuf->resv). This is used to allow poll() to wait upon outstanding rendering (or just query the current status of rendering). The dma-buf sync ioctl allows userspace to prepare the dma-buf for CPU access, which should include waiting upon rendering. (Some drivers may need to do more work to ensure that the dma-buf mmap is coherent as well as complete.) Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: Daniel Vetter <daniel.vetter(a)ffwll.ch> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org Cc: linux-kernel(a)vger.kernel.org --- I'm wondering whether it makes sense just to always do the wait first. It is one of the first operations every driver has to make. A driver that wants to implement it differently (e.g. they can special case native waits) will still require a wait on the reservation object to finish external rendering. -Chris --- drivers/dma-buf/dma-buf.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index ddaee60ae52a..123f14b8e882 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -586,6 +586,22 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, } EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); +static int __dma_buf_begin_cpu_access(struct dma_buf *dmabuf, + enum dma_data_direction direction) +{ + bool write = (direction == DMA_BIDIRECTIONAL || + direction == DMA_TO_DEVICE); + struct reservation_object *resv = dma_buf->resv; + long ret; + + /* Wait on any implicit rendering fences */ + ret = reservation_object_wait_timeout_rcu(resv, write, true, + MAX_SCHEDULE_TIMEOUT); + if (ret < 0) + return ret; + + return 0; +} /** * dma_buf_begin_cpu_access - Must be called before accessing a dma_buf from the @@ -607,6 +623,8 @@ int dma_buf_begin_cpu_access(struct dma_buf *dmabuf, if (dmabuf->ops->begin_cpu_access) ret = dmabuf->ops->begin_cpu_access(dmabuf, direction); + else + ret = __dma_buf_begin_cpu_access(dmabuf, direction); return ret; } -- 2.8.1

9 years, 10 months

[RFC PATCH 0/4] Ion caching (yet again) proof of concept

by Laura Abbott

Hi, I've been (once again) looking at alternate caching models for Ion. Part of this work is also to make Ion fit better in to the dma_buf model. Ion is a bit unusual for dma_buf. Most drivers that support dma_buf have two parts: exporting buffers that a driver allocates and importing buffers allocated elsewhere for use by the driver. Ion is basically designed to export only and not import buffers from other drivers (the need for import is also on my TODO list) Even more unusual, there is no actual 'driver' to map into. Ion currently does nothing except pass back the same sg_table each time without calling dma_map. The description of the .map_dma_buf function in dma_buf_ops * @map_dma_buf: returns list of scatter pages allocated, increases usecount * of the buffer. Requires atleast one attach to be called * before. Returned sg list should already be mapped into * _device_ address space. This call may sleep. May also return * -EINTR. Should return -EINVAL if attach hasn't been called yet. So Ion is definitely not doing this correctly. This ties back into correcting the caching model. If we call dma_map_sg/dma_unmap_sg with begin_cpu_access, this should be enough to allow the caches to always be properly synchronized and means we can drop the various dma_sync calls floating around. This is going to violate one of the big fat comments in ion_buffer_create /* * this will set up dma addresses for the sglist -- it is not * technically correct as per the dma api -- a specific * device isn't really taking ownership here. However, in practice on * our systems the only dma_address space is physical addresses. * Additionally, we can't afford the overhead of invalidating every * allocation via dma_map_sg. The implicit contract here is that * memory coming from the heaps is ready for dma, ie if it has a * cached mapping that mapping has been invalidated */ for_each_sg(buffer->sg_table->sgl, sg, buffer->sg_table->nents, i) { sg_dma_address(sg) = sg_phys(sg); sg_dma_len(sg) = sg->length; } The overhead of invalidating is a valid concern. I'm hoping that the architecture has either evolved such that this won't be a problem or we can figure out some clever use of DMA_ATTR_SKIP_CPU_SYNC. As part of this, I'm considering dropping the fault synchronization. If we have explicit use begin_cpu_access and use of the dma_buf sync ioctls, I don't think it should be necessary. I have a 'pre-RFC' tree at https://pagure.io/kernel-ion/branch/ion_cache_proof_dec14 Yes, the patches are not bisectable and there is more to be done. These have been compile tested only and haven't been hooked up to anything to actually run (another actually big TODO). I'm mostly looking for feedback if this looks like the right direction and if there are going to be major problems with this approach. I don't actually anticipate this getting merged into drivers/staging/android/ion but this is the easiest way to continue discussion. Thanks, Laura Laura Abbott (4): staging: android: ion: Some cleanup staging: android: ion: Duplicate sg_table staging: android: ion: Remove page faulting support staging: android: ion: Call dma_map_sg for syncing and mapping drivers/staging/android/ion/ion-ioctl.c | 6 - drivers/staging/android/ion/ion.c | 251 ++++++++---------------- drivers/staging/android/ion/ion.h | 5 +- drivers/staging/android/ion/ion_carveout_heap.c | 16 +- drivers/staging/android/ion/ion_chunk_heap.c | 15 +- drivers/staging/android/ion/ion_cma_heap.c | 5 +- drivers/staging/android/ion/ion_page_pool.c | 3 - drivers/staging/android/ion/ion_priv.h | 4 +- drivers/staging/android/ion/ion_system_heap.c | 14 +- 9 files changed, 90 insertions(+), 229 deletions(-) -- 2.7.4

9 years, 11 months

Follow up on Ion from LPC

by Laura Abbott

Hi, At LPC, I proposed a moratorium on new Ion features because of issues preventing Ion ever moving out of staging. Among other problems, the Ion caching model hasn't made much progress to a solution that is widely accepted and there are still problems with devicetree support. There were no strong objections to this proposal so I propose continuing with a moratorium for at least the next 6 months to a year to actually work on a new architecture. If this hasn't made much progress by then I plan to hand off Ion to someone else to try other approaches. There's been some discussion about a Unix Device Memory Allocator https://github.com/cubanismo/allocator . Ideally, this would be a complete replacement for Ion. This means capturing Ion or Ion-like requirements. The current proposal mostly focuses on userspace requirements and assumes Ion is just acting as an enumerator of various memory to allocate. This is a good direction. Ideally some of the Ion kernel code could be leveraged for a 'generic device memory allocator'. This device allocator should also be support use cases such as the SMAF (secure memory allocation framework) which has also been a work in progress. One of the big open problems, as mentioned above, is the caching model. Specifying an uncached buffer at allocation time requires doing cache operations outside of the DMA framework which makes a bunch of maintainers unhappy. None of the arguments I've given for justification have really stuck which is a good sign that Ion should probably not be doing cache operations. If we ignore the Ion page pooling feature, this could be fixed by requiring that drivers call dma_buf_map and calling dma_map there. This gets tricker when drivers want to call mmap from userspace before passing the buffer down to ensure coherency. This model will need some more thought and possibly integration with Android. I'd like to keep using linaro-mm-sig as a mailing list for Ion discussion as well as drivers-devel. If it would help to have another place for tracking/discussion I can see about setting that up as well. Thanks, Laura

9 years, 11 months

[PATCH -next] dma-buf/sw_sync: fix non static symbol warning

by Wei Yongjun

From: Wei Yongjun <weiyongjun1(a)huawei.com> Fixes the following sparse warning: drivers/dma-buf/sw_sync.c:87:22: warning: symbol 'sync_timeline_create' was not declared. Should it be static? Signed-off-by: Wei Yongjun <weiyongjun1(a)huawei.com> --- drivers/dma-buf/sw_sync.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c index 82e0ca4..7aa4d7b 100644 --- a/drivers/dma-buf/sw_sync.c +++ b/drivers/dma-buf/sw_sync.c @@ -84,7 +84,7 @@ static inline struct sync_pt *dma_fence_to_sync_pt(struct dma_fence *fence) * Creates a new sync_timeline. Returns the sync_timeline object or NULL in * case of error. */ -struct sync_timeline *sync_timeline_create(const char *name) +static struct sync_timeline *sync_timeline_create(const char *name) { struct sync_timeline *obj;

10 years

[RFC 0/6] Module for tracking/accounting shared memory buffers

by Ruchi Kandoi

This patchstack introduces a new "memtrack" module for tracking and accounting memory exported to userspace as shared buffers, like dma-buf fds or GEM handles. Any process holding a reference to these buffers will keep the kernel from reclaiming its backing pages. mm counters don't provide a complete picture of these allocations, since they only account for pages that are mapped into a process's address space. This problem is especially bad for systems like Android that use dma-buf fds to share graphics and multimedia buffers between processes: these allocations are often large, have complex sharing patterns, and are rarely mapped into every process that holds a reference to them. memtrack maintains a per-process list of shared buffer references, which is exported to userspace as /proc/[pid]/memtrack. Buffers can be optionally "tagged" with a short string: for example, Android userspace would use this tag to identify whether buffers were allocated on behalf of the camera stack, GL, etc. memtrack also exports the VMAs associated with these buffers so that pages already included in the process's mm counters aren't double-counted. Shared-buffer allocators can hook into memtrack by embedding struct memtrack_buffer in their buffer metadata, calling memtrack_buffer_{init,remove} at buffer allocation and free time, and memtrack_buffer_{install,uninstall} when a userspace process takes or drops a reference to the buffer. For fd-backed buffers like dma-bufs, hooks in fdtable.c and fork.c automatically notify memtrack when references are added or removed from a process's fd table. This patchstack adds memtrack hooks into dma-buf and ion. If there's upstream interest in memtrack, it can be extended to other memory allocators as well, such as GEM implementations. Greg Hackmann (1): drivers: staging: ion: add ION_IOC_TAG ioctl Ruchi Kandoi (5): fs: add installed and uninstalled file_operations drivers: misc: add memtrack dma-buf: add memtrack support memtrack: Adds the accounting to keep track of all mmaped/unmapped pages. memtrack: Add memtrack accounting for forked processes. drivers/android/binder.c | 4 +- drivers/dma-buf/dma-buf.c | 37 +++ drivers/misc/Kconfig | 16 + drivers/misc/Makefile | 1 + drivers/misc/memtrack.c | 516 ++++++++++++++++++++++++++++++++ drivers/staging/android/ion/ion-ioctl.c | 17 ++ drivers/staging/android/ion/ion.c | 60 +++- drivers/staging/android/ion/ion_priv.h | 2 + drivers/staging/android/uapi/ion.h | 25 ++ fs/file.c | 38 ++- fs/open.c | 2 +- fs/proc/base.c | 4 + include/linux/dma-buf.h | 5 + include/linux/fdtable.h | 4 +- include/linux/fs.h | 2 + include/linux/memtrack.h | 130 ++++++++ include/linux/mm.h | 3 + include/linux/sched.h | 3 + kernel/fork.c | 23 +- 19 files changed, 875 insertions(+), 17 deletions(-) create mode 100644 drivers/misc/memtrack.c create mode 100644 include/linux/memtrack.h -- 2.8.0.rc3.226.g39d4020

10 years

[PATCH v10 0/3] Secure Memory Allocation Framework

by Benjamin Gaignard

version 10 changes: - rebased on kernel 4.8 tag - minor typo fix version 9 changes: - rebased on 4.8-rc5 - struct dma_attrs doesn't exist anymore so update CMA allocator to compile with new dma_*_attr functions - add example SMAF use case in cover letter version 8 changes: - rework of the structures used within ioctl by adding a version field and padding to be futur proof - rename fake secure moduel to test secure module - fix the various remarks done on the previous patcheset version 7 changes: - rebased on kernel 4.6-rc7 - simplify secure module API - add vma ops to be able to detect mmap/munmap calls - add ioctl to get number and allocator names - update libsmaf with adding tests https://git.linaro.org/people/benjamin.gaignard/libsmaf.git - add debug log in fake secure module version 6 changes: - rebased on kernel 4.5-rc4 - fix mmapping bug while requested allocation size isn't a a multiple of PAGE_SIZE (add a test for this in libsmaf) version 5 changes: - rebased on kernel 4.3-rc6 - rework locking schema and make handle status use an atomic_t - add a fake secure module to allow performing tests without trusted environment version 4 changes: - rebased on kernel 4.3-rc3 - fix missing EXPORT_SYMBOL for smaf_create_handle() version 3 changes: - Remove ioctl for allocator selection instead provide the name of the targeted allocator with allocation request. Selecting allocator from userland isn't the prefered way of working but is needed when the first user of the buffer is a software component. - Fix issues in case of error while creating smaf handle. - Fix module license. - Update libsmaf and tests to care of the SMAF API evolution https://git.linaro.org/people/benjamin.gaignard/libsmaf.git version 2 changes: - Add one ioctl to allow allocator selection from userspace. This is required for the uses case where the first user of the buffer is a software IP which can't perform dma_buf attachement. - Add name and ranking to allocator structure to be able to sort them. - Create a tiny library to test SMAF: https://git.linaro.org/people/benjamin.gaignard/libsmaf.git - Fix one issue when try to secure buffer without secure module registered SMAF aim to solve two problems: allocating memory that fit with hardware IPs constraints and secure those data from bus point of view. One example of SMAF usage is camera preview: on SoC you may use either an USB webcam or the built-in camera interface and the frames could be send directly to the dipslay Ip or handle by GPU. Most of USB interfaces and GPU have mmu but almost all built-in camera interace and display Ips don't have mmu so when selecting how allocate buffer you need to be aware of each devices constraints (contiguous memroy, stride, boundary, alignment ...). ION has solve this problem by let userland decide which allocator (heap) to use but this require to adapt userland for each platform and sometime for each use case. To be sure to select the best allocation method for devices SMAF implement deferred allocation mechanism: memory allocation is only done when the first device effectively required it. Allocator modules have to implement a match() to let SMAF know if they are compatibles with devices needs. This patch set provide an example of allocator module which use dma_{alloc/free/mmap}_attrs() and check if at least one device have coherent_dma_mask set to DMA_BIT_MASK(32) in match function. In the same camera preview use case, SMAF allow to protect the data from being read by unauthorized IPs (i.e. a malware to dump camera stream). Until now I have only see access rights protection at process/thread level (PKeys/MPK) or on file (SELinux) but nothing allow to drive data bus firewalls. SMAF propose an interface to control and implement those firewalls. Like IOMMU, firewalls IPs can help to protect memory from malicious/faulty devices that are attempting DMA attacks. Secure modules are responsibles of granting and revoking devices access rights on the memory. Secure module is also called to check if CPU map memory into kernel and user address spaces. An example of secure module implementation can be found here: http://git.linaro.org/people/benjamin.gaignard/optee-sdp.git This code isn't yet part of the patch set because it depends on generic TEE which is still under discussion (https://lwn.net/Articles/644646/) For allocation part of SMAF code I get inspirated by Sumit Semwal work about constraint aware allocator. Benjamin Gaignard (3): create SMAF module SMAF: add CMA allocator SMAF: add test secure module drivers/Kconfig | 2 + drivers/Makefile | 1 + drivers/smaf/Kconfig | 17 + drivers/smaf/Makefile | 3 + drivers/smaf/smaf-cma.c | 186 ++++++++++ drivers/smaf/smaf-core.c | 818 +++++++++++++++++++++++++++++++++++++++++ drivers/smaf/smaf-testsecure.c | 90 +++++ include/linux/smaf-allocator.h | 45 +++ include/linux/smaf-secure.h | 65 ++++ include/uapi/linux/smaf.h | 85 +++++ 10 files changed, 1312 insertions(+) create mode 100644 drivers/smaf/Kconfig create mode 100644 drivers/smaf/Makefile create mode 100644 drivers/smaf/smaf-cma.c create mode 100644 drivers/smaf/smaf-core.c create mode 100644 drivers/smaf/smaf-testsecure.c create mode 100644 include/linux/smaf-allocator.h create mode 100644 include/linux/smaf-secure.h create mode 100644 include/uapi/linux/smaf.h -- 1.9.1

10 years, 1 month

[PATCH 00/15] improve function-level documentation

by Julia Lawall

These patches fix cases where the documentation above a function definition is not consistent with the function header. Issues are detected using the semantic patch below (http://coccinelle.lip6.fr/). Basically, the semantic patch parses a file to find comments, then matches each function header, and checks that the name and parameter list in the function header are compatible with the comment that preceeds it most closely. // <smpl> @initialize:ocaml@ @@ let tbl = ref [] let fnstart = ref [] let success = Hashtbl.create 101 let thefile = ref "" let parsed = ref [] let nea = ref [] let parse file = thefile := List.nth (Str.split (Str.regexp "linux-next/") file) 1; let i = open_in file in let startline = ref 0 in let fn = ref "" in let ids = ref [] in let rec inside n = let l = input_line i in let n = n + 1 in match Str.split_delim (Str.regexp_string "*/") l with before::after::_ -> (if not (!fn = "") then tbl := (!startline,n,!fn,List.rev !ids)::!tbl); startline := 0; fn := ""; ids := []; outside n | _ -> (match Str.split (Str.regexp "[ \t]+") l with "*"::name::rest -> let len = String.length name in (if !fn = "" && len > 2 && String.sub name (len-2) 2 = "()" then fn := String.sub name 0 (len-2) else if !fn = "" && (not (rest = [])) && List.hd rest = "-" then if String.get name (len-1) = ':' then fn := String.sub name 0 (len-1) else fn := name else if not(!fn = "") && len > 2 && String.get name 0 = '@' && String.get name (len-1) = ':' then ids := (String.sub name 1 (len-2)) :: !ids); | _ -> ()); inside n and outside n = let l = input_line i in let n = n + 1 in if String.length l > 2 && String.sub l 0 3 = "/**" then begin startline := n; inside n end else outside n in try outside 0 with End_of_file -> () let hashadd tbl k v = let cell = try Hashtbl.find tbl k with Not_found -> let cell = ref [] in Hashtbl.add tbl k cell; cell in cell := v :: !cell @script:ocaml@ @@ tbl := []; fnstart := []; Hashtbl.clear success; parsed := []; nea := []; parse (List.hd (Coccilib.files())) @r@ identifier f; position p; @@ f@p(...) { ... } @script:ocaml@ p << r.p; f << r.f; @@ parsed := f :: !parsed; fnstart := (List.hd p).line :: !fnstart @param@ identifier f; type T; identifier i; parameter list[n] ps; parameter list[n1] ps1; position p; @@ f@p(ps,T i,ps1) { ... } @script:ocaml@ @@ tbl := List.rev (List.sort compare !tbl) @script:ocaml@ p << param.p; f << param.f; @@ let myline = (List.hd p).line in let prevline = List.fold_left (fun prev x -> if x < myline then max x prev else prev) 0 !fnstart in let _ = List.exists (function (st,fn,nm,ids) -> if prevline < st && myline > st && prevline < fn && myline > fn then begin (if not (String.lowercase f = String.lowercase nm) then Printf.printf "%s:%d %s doesn't match preceding comment: %s\n" !thefile myline f nm); true end else false) !tbl in () @script:ocaml@ p << param.p; n << param.n; n1 << param.n1; i << param.i; f << param.f; @@ let myline = (List.hd p).line in let prevline = List.fold_left (fun prev x -> if x < myline then max x prev else prev) 0 !fnstart in let _ = List.exists (function (st,fn,nm,ids) -> if prevline < st && myline > st && prevline < fn && myline > fn then begin (if List.mem i ids then hashadd success (st,fn,nm) i); (if ids = [] (* arg list seems not obligatory *) then () else if not (List.mem i ids) then Printf.printf "%s:%d %s doesn't appear in ids: %s\n" !thefile myline i (String.concat " " ids) else if List.length ids <= n || List.length ids <= n1 then (if not (List.mem f !nea) then begin nea := f :: !nea; Printf.printf "%s:%d %s not enough args\n" !thefile myline f; end) else let foundid = List.nth ids n in let efoundid = List.nth (List.rev ids) n1 in if not(foundid = i || efoundid = i) then Printf.printf "%s:%d %s wrong arg in position %d: %s\n" !thefile myline i n foundid); true end else false) !tbl in () @script:ocaml@ @@ List.iter (function (st,fn,nm,ids) -> if List.mem nm !parsed then let entry = try !(Hashtbl.find success (st,fn,nm)) with Not_found -> [] in List.iter (fun id -> if not (List.mem id entry) && not (id = "...") then Printf.printf "%s:%d %s not used\n" !thefile st id) ids) !tbl // </smpl> --- drivers/clk/keystone/pll.c | 4 ++-- drivers/clk/sunxi/clk-mod0.c | 2 +- drivers/clk/tegra/cvb.c | 10 +++++----- drivers/dma-buf/sw_sync.c | 6 +++--- drivers/gpu/drm/gma500/intel_i2c.c | 3 +-- drivers/gpu/drm/omapdrm/omap_drv.c | 4 ++-- drivers/irqchip/irq-metag-ext.c | 1 - drivers/irqchip/irq-vic.c | 1 - drivers/mfd/tc3589x.c | 4 ++-- drivers/power/supply/ab8500_fg.c | 8 ++++---- drivers/power/supply/abx500_chargalg.c | 1 + drivers/power/supply/intel_mid_battery.c | 2 +- drivers/power/supply/power_supply_core.c | 4 ++-- fs/crypto/crypto.c | 4 ++-- fs/crypto/fname.c | 4 ++-- fs/ubifs/file.c | 2 +- fs/ubifs/gc.c | 2 +- fs/ubifs/lprops.c | 2 +- fs/ubifs/lpt_commit.c | 4 +--- fs/ubifs/replay.c | 2 +- lib/kobject_uevent.c | 6 +++--- lib/lru_cache.c | 4 ++-- lib/nlattr.c | 2 +- 23 files changed, 39 insertions(+), 43 deletions(-)

10 years, 1 month

Re: [Linaro-mm-sig] [PATCH 00/15] improve function-level documentation

by Julia Lawall

On Sat, 1 Oct 2016, Joe Perches wrote: > On Sat, 2016-10-01 at 21:46 +0200, Julia Lawall wrote: > > These patches fix cases where the documentation above a function definition > > is not consistent with the function header. Issues are detected using the > > semantic patch below (http://coccinelle.lip6.fr/). Basically, the semantic > > patch parses a file to find comments, then matches each function header, > > and checks that the name and parameter list in the function header are > > compatible with the comment that preceeds it most closely. > > Hi Julia. > > Would it be possible for a semantic patch to scan for > function definitions where the types do not have > identifiers and update the definitions to match the > declarations? > > For instance, given: > > <some.h> > int foo(int); > > <some.c> > int foo(int bar) > { > return baz; > } > > Could coccinelle output: > > diff a/some.h b/some.h > [] > -int foo(int); > +int foo(int bar); The following seems to work: @r@ identifier f; position p; type T, t; parameter list[n] ps; @@ T f@p(ps,t,...); @s@ identifier r.f,x; type r.T, r.t; parameter list[r.n] ps; @@ T f(ps,t x,...) { ... } @@ identifier r.f, s.x; position r.p; type r.T, r.t; parameter list[r.n] ps; @@ T f@p(ps,t + x ,...); After letting it run for a few minutes without making any effort to include .h files, I get over 2700 changed lines. julia

10 years, 1 month

Re: [Linaro-mm-sig] [Intel-gfx] [PATCH 11/11] dma-buf: Do a fast lockless check for poll with timeout=0

by Daniel Vetter

On Fri, Sep 23, 2016 at 07:59:44PM +0200, Christian König wrote: > Am 23.09.2016 um 17:20 schrieb Chris Wilson: > > On Fri, Sep 23, 2016 at 03:50:44PM +0200, Daniel Vetter wrote: > > > On Mon, Aug 29, 2016 at 08:08:34AM +0100, Chris Wilson wrote: > > > > Currently we install a callback for performing poll on a dma-buf, > > > > irrespective of the timeout. This involves taking a spinlock, as well as > > > > unnecessary work, and greatly reduces scaling of poll(.timeout=0) across > > > > multiple threads. > > > > > > > > We can query whether the poll will block prior to installing the > > > > callback to make the busy-query fast. > > > > > > > > Single thread: 60% faster > > > > 8 threads on 4 (+4 HT) cores: 600% faster > > > > > > > > Still not quite the perfect scaling we get with a native busy ioctl, but > > > > poll(dmabuf) is faster due to the quicker lookup of the object and > > > > avoiding drm_ioctl(). > > > > > > > > Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> > > > > Cc: Sumit Semwal <sumit.semwal(a)linaro.org> > > > > Cc: linux-media(a)vger.kernel.org > > > > Cc: dri-devel(a)lists.freedesktop.org > > > > Cc: linaro-mm-sig(a)lists.linaro.org > > > > Reviewed-by: Daniel Vetter <daniel.vetter(a)ffwll.ch> > > > Need to strike the r-b here, since Christian König pointed out that > > > objects won't magically switch signalling on. > > Oh, it also means that > > > > commit fb8b7d2b9d80e1e71f379e57355936bd2b024be9 > > Author: Jammy Zhou <Jammy.Zhou(a)amd.com> > > Date: Wed Jan 21 18:35:47 2015 +0800 > > > > reservation: wait only with non-zero timeout specified (v3) > > When the timeout value passed to reservation_object_wait_timeout_rcu > > is zero, no wait should be done if the fences are not signaled. > > Return '1' for idle and '0' for busy if the specified timeout is '0' > > to keep consistent with the case of non-zero timeout. > > v2: call fence_put if not signaled in the case of timeout==0 > > v3: switch to reservation_object_test_signaled_rcu > > Signed-off-by: Jammy Zhou <Jammy.Zhou(a)amd.com> > > Reviewed-by: Christian König <christian.koenig(a)amd.com> > > Reviewed-by: Alex Deucher <alexander.deucher(a)amd.com> > > Reviewed-By: Maarten Lankhorst <maarten.lankhorst(a)canonical.com> > > Signed-off-by: Sumit Semwal <sumit.semwal(a)linaro.org> > > > > is wrong. And reservation_object_test_signaled_rcu() is unreliable. > > Ups indeed, that patch is wrong as well. > > I suggest that we just enable the signaling in this case as well. Will you/Zhou take care of this corner case? Just so I can't forget about it ;-) Thanks, Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

10 years, 1 month

[PATCH 10/11] dma-buf: Use seqlock to close RCU race in test_signaled_single

by Chris Wilson

With the seqlock now extended to cover the lookup of the fence and its testing, we can perform that testing solely under the seqlock guard and avoid the effective locking and serialisation of acquiring a reference to the request. As the fence is RCU protected we know it cannot disappear as we test it, the same guarantee that made it safe to acquire the reference previously. The seqlock tests whether the fence was replaced as we are testing it telling us whether or not we can trust the result (if not, we just repeat the test until stable). Signed-off-by: Chris Wilson <chris(a)chris-wilson.co.uk> Cc: Sumit Semwal <sumit.semwal(a)linaro.org> Cc: linux-media(a)vger.kernel.org Cc: dri-devel(a)lists.freedesktop.org Cc: linaro-mm-sig(a)lists.linaro.org --- drivers/dma-buf/reservation.c | 32 ++++---------------------------- 1 file changed, 4 insertions(+), 28 deletions(-) diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index e74493e7332b..1ddffa5adb5a 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -442,24 +442,6 @@ unlock_retry: } EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu); - -static inline int -reservation_object_test_signaled_single(struct fence *passed_fence) -{ - struct fence *fence, *lfence = passed_fence; - int ret = 1; - - if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) { - fence = fence_get_rcu(lfence); - if (!fence) - return -1; - - ret = !!fence_is_signaled(fence); - fence_put(fence); - } - return ret; -} - /** * reservation_object_test_signaled_rcu - Test if a reservation object's * fences have been signaled. @@ -474,7 +456,7 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, bool test_all) { unsigned seq, shared_count; - int ret; + bool ret; rcu_read_lock(); retry: @@ -494,10 +476,8 @@ retry: for (i = 0; i < shared_count; ++i) { struct fence *fence = rcu_dereference(fobj->shared[i]); - ret = reservation_object_test_signaled_single(fence); - if (ret < 0) - goto retry; - else if (!ret) + ret = fence_is_signaled(fence); + if (!ret) break; } @@ -509,11 +489,7 @@ retry: struct fence *fence_excl = rcu_dereference(obj->fence_excl); if (fence_excl) { - ret = reservation_object_test_signaled_single( - fence_excl); - if (ret < 0) - goto retry; - + ret = fence_is_signaled(fence_excl); if (read_seqcount_retry(&obj->seq, seq)) goto retry; } -- 2.9.3

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