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Message-ID: <f03c1b59-e024-40d8-5fee-02d8d660a058@amd.com>
Date: Mon, 17 Oct 2022 16:50:39 +0200
From: Christian König <christian.koenig@....com>
To: Arvind Yadav <Arvind.Yadav@....com>, andrey.grodzovsky@....com,
shashank.sharma@....com, amaranath.somalapuram@....com,
Arunpravin.PaneerSelvam@....com, sumit.semwal@...aro.org,
gustavo@...ovan.org, airlied@...ux.ie, daniel@...ll.ch,
linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linaro-mm-sig@...ts.linaro.org, linux-kernel@...r.kernel.org,
steven.price@....com
Subject: Re: [PATCH v3] drm/sched: Fix kernel NULL pointer dereference error
Am 17.10.22 um 16:30 schrieb Arvind Yadav:
> -This is purely a timing issue. Here, sometimes Job free
> is happening before the job is done.
> To fix this issue moving 'dma_fence_cb' callback from
> job(struct drm_sched_job) to scheduler fence (struct drm_sched_fence).
>
> - Added drm_sched_fence_set_parent() function(and others *_parent_cb)
> in sched_fence.c. Moved parent fence intilization and callback
> installation into this (this just cleanup).
>
>
> BUG: kernel NULL pointer dereference, address: 0000000000000088
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 2 PID: 0 Comm: swapper/2 Not tainted 6.0.0-rc2-custom #1
> Arvind : [dma_fence_default_wait _START] timeout = -1
> Hardware name: AMD Dibbler/Dibbler, BIOS RDB1107CC 09/26/2018
> RIP: 0010:drm_sched_job_done.isra.0+0x11/0x140 [gpu_sched]
> Code: 8b fe ff ff be 03 00 00 00 e8 7b da b7 e3 e9 d4 fe ff ff 66 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 49 89 fc 53 <48> 8b 9f 88 00 00 00 f0 ff 8b f0 00 00 00 48 8b 83 80 01 00 00 f0
> RSP: 0018:ffffb1b1801d4d38 EFLAGS: 00010087
> RAX: ffffffffc0aa48b0 RBX: ffffb1b1801d4d70 RCX: 0000000000000018
> RDX: 000036c70afb7c1d RSI: ffff8a45ca413c60 RDI: 0000000000000000
> RBP: ffffb1b1801d4d50 R08: 00000000000000b5 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: ffffb1b1801d4d70 R14: ffff8a45c4160000 R15: ffff8a45c416a708
> FS: 0000000000000000(0000) GS:ffff8a48a0a80000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000088 CR3: 000000014ad50000 CR4: 00000000003506e0
> Call Trace:
> <IRQ>
> drm_sched_job_done_cb+0x12/0x20 [gpu_sched]
> dma_fence_signal_timestamp_locked+0x7e/0x110
> dma_fence_signal+0x31/0x60
> amdgpu_fence_process+0xc4/0x140 [amdgpu]
> gfx_v9_0_eop_irq+0x9d/0xd0 [amdgpu]
> amdgpu_irq_dispatch+0xb7/0x210 [amdgpu]
> amdgpu_ih_process+0x86/0x100 [amdgpu]
> amdgpu_irq_handler+0x24/0x60 [amdgpu]
> __handle_irq_event_percpu+0x4b/0x190
> handle_irq_event_percpu+0x15/0x50
> handle_irq_event+0x39/0x60
> handle_edge_irq+0xaf/0x210
> __common_interrupt+0x6e/0x110
> common_interrupt+0xc1/0xe0
> </IRQ>
> <TASK>
>
> Signed-off-by: Arvind Yadav <Arvind.Yadav@....com>
> ---
>
> Changes in v2: Moving 'dma_fence_cb' callback from
> job(struct drm_sched_job) to scheduler fence(struct drm_sched_fence)
> instead of adding NULL check for s_fence.
>
> Changes in v3: Added drm_sched_fence_set_parent() function(and others *_parent_cb)
> in sched_fence.c. Moved parent fence intilization and callback
> installation into this (this just cleanup).
>
> ---
> drivers/gpu/drm/scheduler/sched_fence.c | 53 +++++++++++++++++++++++++
> drivers/gpu/drm/scheduler/sched_main.c | 38 +++++-------------
> include/drm/gpu_scheduler.h | 12 +++++-
> 3 files changed, 72 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_fence.c b/drivers/gpu/drm/scheduler/sched_fence.c
> index 7fd869520ef2..f6808f363261 100644
> --- a/drivers/gpu/drm/scheduler/sched_fence.c
> +++ b/drivers/gpu/drm/scheduler/sched_fence.c
> @@ -77,6 +77,59 @@ static void drm_sched_fence_free_rcu(struct rcu_head *rcu)
> if (!WARN_ON_ONCE(!fence))
> kmem_cache_free(sched_fence_slab, fence);
> }
Please add an empty line here.
> +/**
> + * drm_sched_job_done_cb - the callback for a done job
> + * @f: fence
> + * @cb: fence callbacks
> + */
> +static void drm_sched_job_done_cb(struct dma_fence *f, struct dma_fence_cb *cb)
Probably best to rename this to something like drm_sched_fence_parent_cb().
> +{
> + struct drm_sched_fence *s_fence = container_of(cb, struct drm_sched_fence,
> + cb);
> + struct drm_gpu_scheduler *sched = s_fence->sched;
> +
> + atomic_dec(&sched->hw_rq_count);
> + atomic_dec(sched->score);
> +
> + dma_fence_get(&s_fence->finished);
We should probably make sure that this reference is taken before
installing the callback.
> + drm_sched_fence_finished(s_fence);
> + dma_fence_put(&s_fence->finished);
> + wake_up_interruptible(&sched->wake_up_worker);
> +}
> +
> +int drm_sched_fence_add_parent_cb(struct dma_fence *fence,
> + struct drm_sched_fence *s_fence)
> +{
> + return dma_fence_add_callback(fence, &s_fence->cb,
> + drm_sched_job_done_cb);
> +}
> +
> +bool drm_sched_fence_remove_parent_cb(struct drm_sched_fence *s_fence)
> +{
> + return dma_fence_remove_callback(s_fence->parent,
> + &s_fence->cb);
> +}
Do we really need separate functions for that?
> +
> +/**
> + * drm_sched_fence_set_parent - set the parent fence and add the callback
> + * fence: pointer to the hw fence
> + * @s_fence: pointer to the fence
Reverse the parameter order, s_fence is the object we work on.
> + *
> + * Set the parent fence and intall the callback for a done job.
You need to document that we take the reference of the parent fence.
> + */
> +int drm_sched_fence_set_parent(struct dma_fence *fence,
> + struct drm_sched_fence *s_fence)
> +{
> + if (s_fence->parent &&
> + dma_fence_remove_callback(s_fence->parent, &s_fence->cb))
> + dma_fence_put(s_fence->parent);
> +
> + s_fence->parent = dma_fence_get(fence);
> + /* Drop for original kref_init of the fence */
> + dma_fence_put(fence);
This leaks the reference to the old parent and the get/put dance is not
optimal either.
Better do something like this.
/* We keep the reference of the parent fence here. */
swap(s_fence->parent, fence);
dma_fence_put(fence);
> + return dma_fence_add_callback(fence, &s_fence->cb,
> + drm_sched_job_done_cb);
> +}
When installing the callback fails we usually call the callback function
instead of returning the error.
>
> /**
> * drm_sched_fence_free - free up an uninitialized fence
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 4cc59bae38dd..cfb52e15f5b0 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -253,13 +253,12 @@ drm_sched_rq_select_entity_fifo(struct drm_sched_rq *rq)
>
> /**
> * drm_sched_job_done - complete a job
> - * @s_job: pointer to the job which is done
> + * @s_fence: pointer to the fence of a done job
> *
> * Finish the job's fence and wake up the worker thread.
> */
> -static void drm_sched_job_done(struct drm_sched_job *s_job)
> +static void drm_sched_job_done(struct drm_sched_fence *s_fence)
> {
> - struct drm_sched_fence *s_fence = s_job->s_fence;
> struct drm_gpu_scheduler *sched = s_fence->sched;
>
> atomic_dec(&sched->hw_rq_count);
> @@ -273,18 +272,6 @@ static void drm_sched_job_done(struct drm_sched_job *s_job)
> wake_up_interruptible(&sched->wake_up_worker);
> }
>
> -/**
> - * drm_sched_job_done_cb - the callback for a done job
> - * @f: fence
> - * @cb: fence callbacks
> - */
> -static void drm_sched_job_done_cb(struct dma_fence *f, struct dma_fence_cb *cb)
> -{
> - struct drm_sched_job *s_job = container_of(cb, struct drm_sched_job, cb);
> -
> - drm_sched_job_done(s_job);
> -}
> -
> /**
> * drm_sched_dependency_optimized - test if the dependency can be optimized
> *
> @@ -505,8 +492,7 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
> list_for_each_entry_safe_reverse(s_job, tmp, &sched->pending_list,
> list) {
> if (s_job->s_fence->parent &&
> - dma_fence_remove_callback(s_job->s_fence->parent,
> - &s_job->cb)) {
> + drm_sched_fence_remove_parent_cb(s_job->s_fence)) {
> dma_fence_put(s_job->s_fence->parent);
> s_job->s_fence->parent = NULL;
Better just call drm_sched_fence_set_parent() with NULL here to clear
the currently installed parent.
This moves all this dance into the scheduler fence code.
> atomic_dec(&sched->hw_rq_count);
> @@ -576,15 +562,14 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
> continue;
>
> if (fence) {
> - r = dma_fence_add_callback(fence, &s_job->cb,
> - drm_sched_job_done_cb);
> + r = drm_sched_fence_add_parent_cb(fence, s_job->s_fence);
> if (r == -ENOENT)
> - drm_sched_job_done(s_job);
> + drm_sched_job_done(s_job->s_fence);
> else if (r)
> DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n",
Completely nuke that here. All of this should be done in the single
drm_sched_fence_set_parent() function.
And an error message is completely superfluous. We just need to handle
the case that the callback can't be installed because the fence is
already signaled.
Regards,
Christian.
> r);
> } else
> - drm_sched_job_done(s_job);
> + drm_sched_job_done(s_job->s_fence);
> }
>
> if (full_recovery) {
> @@ -1049,14 +1034,9 @@ static int drm_sched_main(void *param)
> drm_sched_fence_scheduled(s_fence);
>
> if (!IS_ERR_OR_NULL(fence)) {
> - s_fence->parent = dma_fence_get(fence);
> - /* Drop for original kref_init of the fence */
> - dma_fence_put(fence);
> -
> - r = dma_fence_add_callback(fence, &sched_job->cb,
> - drm_sched_job_done_cb);
> + r = drm_sched_fence_set_parent(fence, s_fence);
> if (r == -ENOENT)
> - drm_sched_job_done(sched_job);
> + drm_sched_job_done(s_fence);
> else if (r)
> DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n",
> r);
> @@ -1064,7 +1044,7 @@ static int drm_sched_main(void *param)
> if (IS_ERR(fence))
> dma_fence_set_error(&s_fence->finished, PTR_ERR(fence));
>
> - drm_sched_job_done(sched_job);
> + drm_sched_job_done(s_fence);
> }
>
> wake_up(&sched->job_scheduled);
> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
> index 1f7d9dd1a444..7258e2fa195f 100644
> --- a/include/drm/gpu_scheduler.h
> +++ b/include/drm/gpu_scheduler.h
> @@ -281,6 +281,10 @@ struct drm_sched_fence {
> * @owner: job owner for debugging
> */
> void *owner;
> + /**
> + * @cb: callback
> + */
> + struct dma_fence_cb cb;
> };
>
> struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
> @@ -300,7 +304,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
> * be scheduled further.
> * @s_priority: the priority of the job.
> * @entity: the entity to which this job belongs.
> - * @cb: the callback for the parent fence in s_fence.
> *
> * A job is created by the driver using drm_sched_job_init(), and
> * should call drm_sched_entity_push_job() once it wants the scheduler
> @@ -325,7 +328,6 @@ struct drm_sched_job {
> atomic_t karma;
> enum drm_sched_priority s_priority;
> struct drm_sched_entity *entity;
> - struct dma_fence_cb cb;
> /**
> * @dependencies:
> *
> @@ -559,6 +561,12 @@ void drm_sched_fence_free(struct drm_sched_fence *fence);
> void drm_sched_fence_scheduled(struct drm_sched_fence *fence);
> void drm_sched_fence_finished(struct drm_sched_fence *fence);
>
> +int drm_sched_fence_add_parent_cb(struct dma_fence *fence,
> + struct drm_sched_fence *s_fence);
> +bool drm_sched_fence_remove_parent_cb(struct drm_sched_fence *s_fence);
> +int drm_sched_fence_set_parent(struct dma_fence *fence,
> + struct drm_sched_fence *s_fence);
> +
> unsigned long drm_sched_suspend_timeout(struct drm_gpu_scheduler *sched);
> void drm_sched_resume_timeout(struct drm_gpu_scheduler *sched,
> unsigned long remaining);
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