Re: [RFC PATCH] drm: gpu: msm: forbid mem reclaim from reset

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (26/03/27 09:08), Rob Clark wrote:
> On Thu, Mar 26, 2026 at 5:18 PM Akhil P Oommen <akhilpo@oss.qualcomm.com> wrote:
> >
> > On 3/26/2026 7:24 AM, Sergey Senozhatsky wrote:
> > > On (26/01/27 16:33), Sergey Senozhatsky wrote:
> > >> We sometimes get into a situtation where GPU hangcheck fails to
> > >> recover GPU:
> > >>
> > >> [..]
> > >> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): hangcheck detected gpu lockup rb 0!
> > >> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): completed fence: 7840161
> > >> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): submitted fence: 7840162
> > >> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): hangcheck detected gpu lockup rb 0!
> > >> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): completed fence: 7840162
> > >> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): submitted fence: 7840163
> > >> [..]
> > >>
> > >> The problem is that msm_job worker is blocked on gpu->lock
> > >>
> > >> INFO: task ring0:155 blocked for more than 122 seconds.
> > >> Not tainted 6.6.99-08727-gaac38b365d2c #1
> > >> task:ring0 state:D stack:0 pid:155 ppid:2 flags:0x00000008
> > >> Call trace:
> > >> __switch_to+0x108/0x208
> > >> schedule+0x544/0x11f0
> > >> schedule_preempt_disabled+0x30/0x50
> > >> __mutex_lock_common+0x410/0x850
> > >> __mutex_lock_slowpath+0x28/0x40
> > >> mutex_lock+0x5c/0x90
> > >> msm_job_run+0x9c/0x140
> > >> drm_sched_main+0x514/0x938
> > >> kthread+0x114/0x138
> > >> ret_from_fork+0x10/0x20
> > >>
> > >> which is owned by recover worker, which is waiting for DMA fences
> > >> from a memory reclaim path, under the very same gpu->lock
> >
> > I am still thinking if there is a better way to handle this. Btw, Rob
> > had a few fixes related to this area recently. Do you think those would
> > help in this scenario?
> 
> For some reason I was thinking we used GFP_ATOMIC or similar in the
> gpu snapshot path.. but we don't :-(
> 
> It does look like we handle allocation failures.  So this is probably
> a better option than fixing up GFP flags everywhere.
> 
> Reviewed-by: Rob Clark <rob.clark@oss.qualcomm.com>

Thanks!

> 
> (and apologies for overlooking this patch earlier)

No worries.