<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style> </head> <body dir="ltr"> <div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> I recently updated amd-staging-drm-next. Apply whatever makes sense for now and it'll naturally fall out in the next rebase.</div> <div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> </div> <div style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> Alex </div> <div id="appendonsend"></div> <hr style="display:inline-block;width:98%" tabindex="-1"> <div id="divRplyFwdMsg" dir="ltr">From: Grodzovsky, Andrey <Andrey.Grodzovsky@amd.com> Sent: Monday, November 25, 2019 7:09 PM To: Deng, Emily <Emily.Deng@amd.com> Cc: dri-devel@lists.freedesktop.org <dri-devel@lists.freedesktop.org>; amd-gfx@lists.freedesktop.org <amd-gfx@lists.freedesktop.org>; Koenig, Christian <Christian.Koenig@amd.com>; steven.price@arm.com <steven.price@arm.com>; Deucher, Alexander <Alexander.Deucher@amd.com> Subject: Re: [PATCH v4] drm/scheduler: Avoid accessing freed bad job. <div> </div> </div> <div class="BodyFragment"> <div class="PlainText">Christian asked to submit it to drm-misc instead of our drm-next to avoid later conflicts with Steven's patch which he mentioned in this thread which is not in drm-next yet. Christian, Alex, once this merged to drm-misc I guess we need to pull all latest changes from there to drm-next so the issue Emily reported can be avoided. Andrey ________________________________________ From: Deng, Emily <Emily.Deng@amd.com> Sent: 25 November 2019 16:44:36 To: Grodzovsky, Andrey Cc: dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org; Koenig, Christian; steven.price@arm.com; Grodzovsky, Andrey Subject: RE: [PATCH v4] drm/scheduler: Avoid accessing freed bad job. [AMD Official Use Only - Internal Distribution Only] Hi Andrey, Seems you didn't submit this patch? Best wishes Emily Deng >-----Original Message----- >From: Andrey Grodzovsky <andrey.grodzovsky@amd.com> >Sent: Monday, November 25, 2019 12:51 PM >Cc: dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org; Koenig, >Christian <Christian.Koenig@amd.com>; Deng, Emily ><Emily.Deng@amd.com>; steven.price@arm.com; Grodzovsky, Andrey ><Andrey.Grodzovsky@amd.com> >Subject: [PATCH v4] drm/scheduler: Avoid accessing freed bad job. > >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@amd.com> >Reviewed-by: Christian König <christian.koenig@amd.com> >Tested-by: Emily Deng <Emily.Deng@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. >-- >2.7.4 </div> </div> </body> </html>