Re: [PATCH] Revert "drm/sched: Use parent fence instead of finished"

[Rob Clark]

On Fri, Dec 2, 2022 at 9:24 AM Arvind Yadav <Arvind.Yadav@xxxxxxx> wrote:
>
> This reverts commit e4dc45b1848bc6bcac31eb1b4ccdd7f6718b3c86.
>
>     This is causing instability on Linus' desktop, and Observed System
>     hung  when running MesaGL benchmark or VK CTS runs.
>
>     netconsole got me the following oops:
>     [ 1234.778760] BUG: kernel NULL pointer dereference, address: 0000000000000088
>     [ 1234.778782] #PF: supervisor read access in kernel mode
>     [ 1234.778787] #PF: error_code(0x0000) - not-present page
>     [ 1234.778791] PGD 0 P4D 0
>     [ 1234.778798] Oops: 0000 [#1] PREEMPT SMP NOPTI
>     [ 1234.778803] CPU: 7 PID: 805 Comm: systemd-journal Not tainted 6.0.0+ #2
>     [ 1234.778809] Hardware name: System manufacturer System Product
>     Name/PRIME X370-PRO, BIOS 5603 07/28/2020
>     [ 1234.778813] RIP: 0010:drm_sched_job_done.isra.0+0xc/0x140 [gpu_sched]
>     [ 1234.778828] Code: aa 0f 1d ce e9 57 ff ff ff 48 89 d7 e8 9d 8f 3f
>     ce e9 4a ff ff ff 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 41 54 55 53
>     48 89 fb <48> 8b af 88 00 00 00 f0 ff 8d f0 00 00 00 48 8b 85 80 01 00
>     00 f0
>     [ 1234.778834] RSP: 0000:ffffabe680380de0 EFLAGS: 00010087
>     [ 1234.778839] RAX: ffffffffc04e9230 RBX: 0000000000000000 RCX: 0000000000000018
>     [ 1234.778897] RDX: 00000ba278e8977a RSI: ffff953fb288b460 RDI: 0000000000000000
>     [ 1234.778901] RBP: ffff953fb288b598 R08: 00000000000000e0 R09: ffff953fbd98b808
>     [ 1234.778905] R10: 0000000000000000 R11: ffffabe680380ff8 R12: ffffabe680380e00
>     [ 1234.778908] R13: 0000000000000001 R14: 00000000ffffffff R15: ffff953fbd9ec458
>     [ 1234.778912] FS:  00007f35e7008580(0000) GS:ffff95428ebc0000(0000)
>     knlGS:0000000000000000
>     [ 1234.778916] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>     [ 1234.778919] CR2: 0000000000000088 CR3: 000000010147c000 CR4: 00000000003506e0
>     [ 1234.778924] Call Trace:
>     [ 1234.778981]  <IRQ>
>     [ 1234.778989]  dma_fence_signal_timestamp_locked+0x6a/0xe0
>     [ 1234.778999]  dma_fence_signal+0x2c/0x50
>     [ 1234.779005]  amdgpu_fence_process+0xc8/0x140 [amdgpu]
>     [ 1234.779234]  sdma_v3_0_process_trap_irq+0x70/0x80 [amdgpu]
>     [ 1234.779395]  amdgpu_irq_dispatch+0xa9/0x1d0 [amdgpu]
>     [ 1234.779609]  amdgpu_ih_process+0x80/0x100 [amdgpu]
>     [ 1234.779783]  amdgpu_irq_handler+0x1f/0x60 [amdgpu]
>     [ 1234.779940]  __handle_irq_event_percpu+0x46/0x190
>     [ 1234.779946]  handle_irq_event+0x34/0x70
>     [ 1234.779949]  handle_edge_irq+0x9f/0x240
>     [ 1234.779954]  __common_interrupt+0x66/0x100
>     [ 1234.779960]  common_interrupt+0xa0/0xc0
>     [ 1234.779965]  </IRQ>
>     [ 1234.779968]  <TASK>
>     [ 1234.779971]  asm_common_interrupt+0x22/0x40
>     [ 1234.779976] RIP: 0010:finish_mkwrite_fault+0x22/0x110
>     [ 1234.779981] Code: 1f 84 00 00 00 00 00 90 0f 1f 44 00 00 41 55 41
>     54 55 48 89 fd 53 48 8b 07 f6 40 50 08 0f 84 eb 00 00 00 48 8b 45 30
>     48 8b 18 <48> 89 df e8 66 bd ff ff 48 85 c0 74 0d 48 89 c2 83 e2 01 48
>     83 ea
>     [ 1234.779985] RSP: 0000:ffffabe680bcfd78 EFLAGS: 00000202
>
>     Revert it for now and figure it out later.

Just fwiw, the issue here is a race against sched_main observing that
the hw fence is signaled and doing job_cleanup and the driver retiring
the job.  I don't think there is a sane way to use the parent fence
without having this race condition so the "figure it out later" is
"don't do that" ;-)

BR,
-R

> Signed-off-by: Arvind Yadav <Arvind.Yadav@xxxxxxx>
> ---
>  drivers/gpu/drm/scheduler/sched_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 820c0c5544e1..ea7bfa99d6c9 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -790,7 +790,7 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
>         job = list_first_entry_or_null(&sched->pending_list,
>                                        struct drm_sched_job, list);
>
> -       if (job && dma_fence_is_signaled(job->s_fence->parent)) {
> +       if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
>                 /* remove job from pending_list */
>                 list_del_init(&job->list);
>
> @@ -802,7 +802,7 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
>
>                 if (next) {
>                         next->s_fence->scheduled.timestamp =
> -                               job->s_fence->parent->timestamp;
> +                               job->s_fence->finished.timestamp;
>                         /* start TO timer for next job */
>                         drm_sched_start_timeout(sched);
>                 }
> --
> 2.25.1
>