[PATCH v4] drm/scheduler: Avoid accessing freed bad job.

Andrey Grodzovsky Andrey.Grodzovsky at amd.com
Tue Dec 3 20:32:43 UTC 2019 

Turns out Steven's patch was already in so i just cherry-picked the 
change from drm-next-misc


Emily - it's in.


Andrey


On 12/3/19 2:59 PM, Deucher, Alexander wrote:
>
> [AMD Official Use Only - Internal Distribution Only]
>
>
> Cherry pick whatever dependencies you need or pick the older version 
> of the patch.  Either way works.
>
> Alex
> ------------------------------------------------------------------------
> *From:* Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com>
> *Sent:* Tuesday, December 3, 2019 2:57 PM
> *To:* Deucher, Alexander <Alexander.Deucher at amd.com>; Deng, Emily 
> <Emily.Deng at amd.com>
> *Cc:* dri-devel at lists.freedesktop.org 
> <dri-devel at lists.freedesktop.org>; amd-gfx at lists.freedesktop.org 
> <amd-gfx at lists.freedesktop.org>; Koenig, Christian 
> <Christian.Koenig at amd.com>; steven.price at arm.com <steven.price at arm.com>
> *Subject:* Re: [PATCH v4] drm/scheduler: Avoid accessing freed bad job.
>
> I don't think i can apply this patch 'as is' as this has dependency on 
> patch by Steven which also wasn't applied yet - 588b982 Steven 
> Price        6 weeks ago    drm: Don't free jobs in 
> wait_event_interruptible()
>
>
> Andrey
>
>
> On 12/3/19 2:44 PM, Deucher, Alexander wrote:
>>
>> [AMD Official Use Only - Internal Distribution Only]
>>
>>
>> Please go ahead an apply whatever version is necessary for 
>> amd-staging-drm-next.
>>
>> Alex
>>
>> ------------------------------------------------------------------------
>> *From:* Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com> 
>> <mailto:Andrey.Grodzovsky at amd.com>
>> *Sent:* Tuesday, December 3, 2019 2:10 PM
>> *To:* Deng, Emily <Emily.Deng at amd.com> <mailto:Emily.Deng at amd.com>; 
>> Deucher, Alexander <Alexander.Deucher at amd.com> 
>> <mailto:Alexander.Deucher at amd.com>
>> *Cc:* dri-devel at lists.freedesktop.org 
>> <mailto:dri-devel at lists.freedesktop.org> 
>> <dri-devel at lists.freedesktop.org> 
>> <mailto:dri-devel at lists.freedesktop.org>; 
>> amd-gfx at lists.freedesktop.org <mailto:amd-gfx at lists.freedesktop.org> 
>> <amd-gfx at lists.freedesktop.org> 
>> <mailto:amd-gfx at lists.freedesktop.org>; Koenig, Christian 
>> <Christian.Koenig at amd.com> <mailto:Christian.Koenig at amd.com>; 
>> steven.price at arm.com <mailto:steven.price at arm.com> 
>> <steven.price at arm.com> <mailto:steven.price at arm.com>
>> *Subject:* Re: [PATCH v4] drm/scheduler: Avoid accessing freed bad job.
>> Yes - Christian just pushed it to drm-next-misc - I guess Alex/Christian
>> didn't pull to amd-staging-drm-next yet.
>>
>> Andrey
>>
>> On 12/2/19 2:24 PM, Deng, Emily wrote:
>> > [AMD Official Use Only - Internal Distribution Only]
>> >
>> > Hi Andrey,
>> >      Seems this patch is still not in amd-staging-drm-next?
>> >
>> > Best wishes
>> > Emily Deng
>> >
>> >
>> >
>> >> -----Original Message-----
>> >> From: Deng, Emily
>> >> Sent: Tuesday, November 26, 2019 4:41 PM
>> >> To: Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com> 
>> <mailto:Andrey.Grodzovsky at amd.com>
>> >> Cc: dri-devel at lists.freedesktop.org 
>> <mailto:dri-devel at lists.freedesktop.org>; 
>> amd-gfx at lists.freedesktop.org <mailto:amd-gfx at lists.freedesktop.org>; 
>> Koenig,
>> >> Christian <Christian.Koenig at amd.com> 
>> <mailto:Christian.Koenig at amd.com>; steven.price at arm.com 
>> <mailto:steven.price at arm.com>
>> >> Subject: RE: [PATCH v4] drm/scheduler: Avoid accessing freed bad job.
>> >>
>> >> [AMD Official Use Only - Internal Distribution Only]
>> >>
>> >> Reviewed-by: Emily Deng <Emily.Deng at amd.com> 
>> <mailto:Emily.Deng at amd.com>
>> >>
>> >>> -----Original Message-----
>> >>> From: Grodzovsky, Andrey <Andrey.Grodzovsky at amd.com> 
>> <mailto:Andrey.Grodzovsky at amd.com>
>> >>> Sent: Tuesday, November 26, 2019 7:37 AM
>> >>> Cc: dri-devel at lists.freedesktop.org 
>> <mailto:dri-devel at lists.freedesktop.org>; 
>> amd-gfx at lists.freedesktop.org <mailto:amd-gfx at lists.freedesktop.org>;
>> >>> Koenig, Christian <Christian.Koenig at amd.com> 
>> <mailto:Christian.Koenig at amd.com>; Deng, Emily
>> >>> <Emily.Deng at amd.com> <mailto:Emily.Deng at amd.com>; 
>> steven.price at arm.com <mailto:steven.price at arm.com>
>> >>> Subject: Re: [PATCH v4] drm/scheduler: Avoid accessing freed bad job.
>> >>>
>> >>> Ping
>> >>>
>> >>> Andrey
>> >>>
>> >>> On 11/25/19 3:51 PM, Andrey Grodzovsky wrote:
>> >>>> Problem:
>> >>>> Due to a race between drm_sched_cleanup_jobs in sched thread and
>> >>>> drm_sched_job_timedout in timeout work there is a possiblity 
>> that bad
>> >>>> job was already freed while still being accessed from the timeout
>> >>>> thread.
>> >>>>
>> >>>> Fix:
>> >>>> Instead of just peeking at the bad job in the mirror list remove it
>> >>>> from the list under lock and then put it back later when we are
>> >>>> garanteed no race with main sched thread is possible which is after
>> >>>> the thread is parked.
>> >>>>
>> >>>> v2: Lock around processing ring_mirror_list in 
>> drm_sched_cleanup_jobs.
>> >>>>
>> >>>> v3: Rebase on top of drm-misc-next. v2 is not needed anymore as
>> >>>> drm_sched_get_cleanup_job already has a lock there.
>> >>>>
>> >>>> v4: Fix comments to relfect latest code in drm-misc.
>> >>>>
>> >>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky at amd.com> 
>> <mailto:andrey.grodzovsky at amd.com>
>> >>>> Reviewed-by: Christian König <christian.koenig at amd.com> 
>> <mailto:christian.koenig at amd.com>
>> >>>> Tested-by: Emily Deng <Emily.Deng at amd.com> 
>> <mailto:Emily.Deng at amd.com>
>> >>>> ---
>> >>>> drivers/gpu/drm/scheduler/sched_main.c | 27
>> >>> +++++++++++++++++++++++++++
>> >>>>    1 file changed, 27 insertions(+)
>> >>>>
>> >>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c
>> >>>> b/drivers/gpu/drm/scheduler/sched_main.c
>> >>>> index 6774955..1bf9c40 100644
>> >>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>> >>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>> >>>> @@ -284,10 +284,21 @@ static void drm_sched_job_timedout(struct
>> >>> work_struct *work)
>> >>>>     unsigned long flags;
>> >>>>
>> >>>>     sched = container_of(work, struct drm_gpu_scheduler,
>> >>>> work_tdr.work);
>> >>>> +
>> >>>> +  /* Protects against concurrent deletion in
>> >>> drm_sched_get_cleanup_job */
>> >>>> + spin_lock_irqsave(&sched->job_list_lock, flags);
>> >>>>     job = list_first_entry_or_null(&sched->ring_mirror_list,
>> >>>>                                    struct drm_sched_job, node);
>> >>>>
>> >>>>     if (job) {
>> >>>> +          /*
>> >>>> +           * Remove the bad job so it cannot be freed by concurrent
>> >>>> +           * drm_sched_cleanup_jobs. It will be reinserted back 
>> after
>> >>> sched->thread
>> >>>> +           * is parked at which point it's safe.
>> >>>> +           */
>> >>>> + list_del_init(&job->node);
>> >>>> + spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> >>>> +
>> >>>> job->sched->ops->timedout_job(job);
>> >>>>
>> >>>>             /*
>> >>>> @@ -298,6 +309,8 @@ static void drm_sched_job_timedout(struct
>> >>> work_struct *work)
>> >>>> job->sched->ops->free_job(job);
>> >>>> sched->free_guilty = false;
>> >>>>             }
>> >>>> +  } else {
>> >>>> + spin_unlock_irqrestore(&sched->job_list_lock, flags);
>> >>>>     }
>> >>>>
>> >>>> spin_lock_irqsave(&sched->job_list_lock, flags); @@ -370,6 +383,20
>> >>>> @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct
>> >>> drm_sched_job *bad)
>> >>>> kthread_park(sched->thread);
>> >>>>
>> >>>>     /*
>> >>>> +   * Reinsert back the bad job here - now it's safe as
>> >>>> +   * drm_sched_get_cleanup_job cannot race against us and 
>> release the
>> >>>> +   * bad job at this point - we parked (waited for) any in progress
>> >>>> +   * (earlier) cleanups and drm_sched_get_cleanup_job will not be
>> >>> called
>> >>>> +   * now until the scheduler thread is unparked.
>> >>>> +   */
>> >>>> +  if (bad && bad->sched == sched)
>> >>>> +          /*
>> >>>> +           * Add at the head of the queue to reflect it was the 
>> earliest
>> >>>> +           * job extracted.
>> >>>> +           */
>> >>>> + list_add(&bad->node, &sched->ring_mirror_list);
>> >>>> +
>> >>>> +  /*
>> >>>>      * Iterate the job list from later to  earlier one and 
>> either deactive
>> >>>>      * their HW callbacks or remove them from mirror list if 
>> they already
>> >>>>      * signaled.
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