From: Andrey Grodzovsky <andrey.grodzovsky@amd.com> To: Hangyu Hua <hbh25y@gmail.com>, yuq825@gmail.com, airlied@linux.ie, daniel@ffwll.ch Cc: dri-devel@lists.freedesktop.org, lima@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] gpu: drm: remove redundant dma_fence_put() when drm_sched_job_add_dependency() fails Date: Tue, 26 Apr 2022 10:55:34 -0400 [thread overview] Message-ID: <e26e6ef8-6665-0b9d-804f-cf107f1788d4@amd.com> (raw) In-Reply-To: <79b198d0-eff2-d658-4b5e-9084a834fc93@gmail.com> On 2022-04-25 22:54, Hangyu Hua wrote: > On 2022/4/25 23:42, Andrey Grodzovsky wrote: >> On 2022-04-25 04:36, Hangyu Hua wrote: >> >>> When drm_sched_job_add_dependency() fails, dma_fence_put() will be >>> called >>> internally. Calling it again after drm_sched_job_add_dependency() >>> finishes >>> may result in a dangling pointer. >>> >>> Fix this by removing redundant dma_fence_put(). >>> >>> Signed-off-by: Hangyu Hua <hbh25y@gmail.com> >>> --- >>> drivers/gpu/drm/lima/lima_gem.c | 1 - >>> drivers/gpu/drm/scheduler/sched_main.c | 1 - >>> 2 files changed, 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/lima/lima_gem.c >>> b/drivers/gpu/drm/lima/lima_gem.c >>> index 55bb1ec3c4f7..99c8e7f6bb1c 100644 >>> --- a/drivers/gpu/drm/lima/lima_gem.c >>> +++ b/drivers/gpu/drm/lima/lima_gem.c >>> @@ -291,7 +291,6 @@ static int lima_gem_add_deps(struct drm_file >>> *file, struct lima_submit *submit) >>> err = drm_sched_job_add_dependency(&submit->task->base, >>> fence); >>> if (err) { >>> - dma_fence_put(fence); >>> return err; >> >> >> Makes sense here >> >> >>> } >>> } >>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c >>> b/drivers/gpu/drm/scheduler/sched_main.c >>> index b81fceb0b8a2..ebab9eca37a8 100644 >>> --- a/drivers/gpu/drm/scheduler/sched_main.c >>> +++ b/drivers/gpu/drm/scheduler/sched_main.c >>> @@ -708,7 +708,6 @@ int >>> drm_sched_job_add_implicit_dependencies(struct drm_sched_job *job, >>> dma_fence_get(fence); >>> ret = drm_sched_job_add_dependency(job, fence); >>> if (ret) { >>> - dma_fence_put(fence); >> >> >> >> Not sure about this one since if you look at the relevant commits - >> 'drm/scheduler: fix drm_sched_job_add_implicit_dependencies' and >> 'drm/scheduler: fix drm_sched_job_add_implicit_dependencies harder' >> You will see that the dma_fence_put here balances the extra >> dma_fence_get >> above >> >> Andrey >> > > I don't think so. I checked the call chain and found no additional > dma_fence_get(). But dma_fence_get() needs to be called before > drm_sched_job_add_dependency() to keep the counter balanced. I don't say there is an additional get, I just say that drm_sched_job_add_dependency doesn't grab an extra reference to the fences it stores so this needs to be done outside and for that drm_sched_job_add_implicit_dependencies->dma_fence_get is called and, if this addition fails you just call dma_fence_put to keep the counter balanced. > On the other hand, dma_fence_get() and dma_fence_put() are meaningless > here if threre is an extra dma_fence_get() beacause counter will not > decrease to 0 during drm_sched_job_add_dependency(). > > I check the call chain as follows: > > msm_ioctl_gem_submit() > -> submit_fence_sync() > -> drm_sched_job_add_implicit_dependencies() Can you maybe trace or print one such example of problematic refcount that you are trying to fix ? I still don't see where is the problem. Andrey > > Thanks, > Hangyu > >> >>> return ret; >>> } >>> }
WARNING: multiple messages have this Message-ID (diff)
From: Andrey Grodzovsky <andrey.grodzovsky@amd.com> To: Hangyu Hua <hbh25y@gmail.com>, yuq825@gmail.com, airlied@linux.ie, daniel@ffwll.ch Cc: lima@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] gpu: drm: remove redundant dma_fence_put() when drm_sched_job_add_dependency() fails Date: Tue, 26 Apr 2022 10:55:34 -0400 [thread overview] Message-ID: <e26e6ef8-6665-0b9d-804f-cf107f1788d4@amd.com> (raw) In-Reply-To: <79b198d0-eff2-d658-4b5e-9084a834fc93@gmail.com> On 2022-04-25 22:54, Hangyu Hua wrote: > On 2022/4/25 23:42, Andrey Grodzovsky wrote: >> On 2022-04-25 04:36, Hangyu Hua wrote: >> >>> When drm_sched_job_add_dependency() fails, dma_fence_put() will be >>> called >>> internally. Calling it again after drm_sched_job_add_dependency() >>> finishes >>> may result in a dangling pointer. >>> >>> Fix this by removing redundant dma_fence_put(). >>> >>> Signed-off-by: Hangyu Hua <hbh25y@gmail.com> >>> --- >>> drivers/gpu/drm/lima/lima_gem.c | 1 - >>> drivers/gpu/drm/scheduler/sched_main.c | 1 - >>> 2 files changed, 2 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/lima/lima_gem.c >>> b/drivers/gpu/drm/lima/lima_gem.c >>> index 55bb1ec3c4f7..99c8e7f6bb1c 100644 >>> --- a/drivers/gpu/drm/lima/lima_gem.c >>> +++ b/drivers/gpu/drm/lima/lima_gem.c >>> @@ -291,7 +291,6 @@ static int lima_gem_add_deps(struct drm_file >>> *file, struct lima_submit *submit) >>> err = drm_sched_job_add_dependency(&submit->task->base, >>> fence); >>> if (err) { >>> - dma_fence_put(fence); >>> return err; >> >> >> Makes sense here >> >> >>> } >>> } >>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c >>> b/drivers/gpu/drm/scheduler/sched_main.c >>> index b81fceb0b8a2..ebab9eca37a8 100644 >>> --- a/drivers/gpu/drm/scheduler/sched_main.c >>> +++ b/drivers/gpu/drm/scheduler/sched_main.c >>> @@ -708,7 +708,6 @@ int >>> drm_sched_job_add_implicit_dependencies(struct drm_sched_job *job, >>> dma_fence_get(fence); >>> ret = drm_sched_job_add_dependency(job, fence); >>> if (ret) { >>> - dma_fence_put(fence); >> >> >> >> Not sure about this one since if you look at the relevant commits - >> 'drm/scheduler: fix drm_sched_job_add_implicit_dependencies' and >> 'drm/scheduler: fix drm_sched_job_add_implicit_dependencies harder' >> You will see that the dma_fence_put here balances the extra >> dma_fence_get >> above >> >> Andrey >> > > I don't think so. I checked the call chain and found no additional > dma_fence_get(). But dma_fence_get() needs to be called before > drm_sched_job_add_dependency() to keep the counter balanced. I don't say there is an additional get, I just say that drm_sched_job_add_dependency doesn't grab an extra reference to the fences it stores so this needs to be done outside and for that drm_sched_job_add_implicit_dependencies->dma_fence_get is called and, if this addition fails you just call dma_fence_put to keep the counter balanced. > On the other hand, dma_fence_get() and dma_fence_put() are meaningless > here if threre is an extra dma_fence_get() beacause counter will not > decrease to 0 during drm_sched_job_add_dependency(). > > I check the call chain as follows: > > msm_ioctl_gem_submit() > -> submit_fence_sync() > -> drm_sched_job_add_implicit_dependencies() Can you maybe trace or print one such example of problematic refcount that you are trying to fix ? I still don't see where is the problem. Andrey > > Thanks, > Hangyu > >> >>> return ret; >>> } >>> }
next prev parent reply other threads:[~2022-04-26 14:56 UTC|newest] Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-25 8:36 [PATCH] gpu: drm: remove redundant dma_fence_put() when drm_sched_job_add_dependency() fails Hangyu Hua 2022-04-25 8:36 ` Hangyu Hua 2022-04-25 15:42 ` Andrey Grodzovsky 2022-04-25 15:42 ` Andrey Grodzovsky 2022-04-26 2:54 ` Hangyu Hua 2022-04-26 2:54 ` Hangyu Hua 2022-04-26 14:48 ` Andrey Grodzovsky 2022-04-26 14:48 ` Andrey Grodzovsky 2022-04-26 14:55 ` Andrey Grodzovsky [this message] 2022-04-26 14:55 ` Andrey Grodzovsky 2022-04-27 2:31 ` Hangyu Hua 2022-04-27 2:31 ` Hangyu Hua 2022-04-27 14:43 ` Andrey Grodzovsky 2022-04-28 8:56 ` Hangyu Hua 2022-04-28 8:56 ` Hangyu Hua 2022-04-28 15:27 ` Andrey Grodzovsky 2022-04-28 15:27 ` Andrey Grodzovsky 2022-04-29 3:03 ` Hangyu Hua 2022-04-29 3:03 ` Hangyu Hua 2022-04-29 16:34 ` Andrey Grodzovsky 2022-04-29 16:34 ` Andrey Grodzovsky
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