On 17/09/2019 09:42, Koenig, Christian wrote:
Hi Steven,
thought about that issue a bit more and I think I came up with a solution.
What you could do is to split up drm_sched_cleanup_jobs() into two
functions.
One that checks if jobs to be cleaned up are present and one which does
the actual cleanup.
This way we could call drm_sched_cleanup_jobs() outside of the
wait_event_interruptible().
Yes that seems like a good solution - there doesn't seem to be a good
reason why the actual job cleanup needs to be done within the
wait_event_interruptible() condition. I did briefly attempt that before,
but I couldn't work out exactly what the condition is which should cause
the wake (my initial attempt caused continuous wake-ups).
I'm not back in the office until Monday, but I'll have another go then
at spitting the checking and the actual freeing of the jobs.
Thanks,
Steve
Regards,
Christian.
Am 13.09.19 um 16:50 schrieb Steven Price:
Hi,
I hit the below splat randomly with panfrost. From what I can tell this
is a more general issue which would affect other drivers.
----8<-----
[58604.913130] ------------[ cut here ]------------
[58604.918590] WARNING: CPU: 1 PID: 1758 at kernel/sched/core.c:6556 __might_sleep+0x74/0x98
[58604.927965] do not call blocking ops when !TASK_RUNNING; state=1 set at [<0c590494>] prepare_to_wait_event+0x104/0x164
[58604.940047] Modules linked in: panfrost gpu_sched
[58604.945370] CPU: 1 PID: 1758 Comm: pan_js Not tainted 5.3.0-rc1+ #13
[58604.952500] Hardware name: Rockchip (Device Tree)
[58604.957815] [<c0111150>] (unwind_backtrace) from [<c010c99c>] (show_stack+0x10/0x14)
[58604.966521] [<c010c99c>] (show_stack) from [<c07adbb4>] (dump_stack+0x9c/0xd4)
[58604.974639] [<c07adbb4>] (dump_stack) from [<c0121da8>] (__warn+0xe8/0x104)
[58604.982462] [<c0121da8>] (__warn) from [<c0121e08>] (warn_slowpath_fmt+0x44/0x6c)
[58604.990867] [<c0121e08>] (warn_slowpath_fmt) from [<c014eccc>] (__might_sleep+0x74/0x98)
[58604.999973] [<c014eccc>] (__might_sleep) from [<c07c73d8>] (__mutex_lock+0x38/0x948)
[58605.008690] [<c07c73d8>] (__mutex_lock) from [<c07c7d00>] (mutex_lock_nested+0x18/0x20)
[58605.017841] [<c07c7d00>] (mutex_lock_nested) from [<bf00b54c>] (panfrost_gem_free_object+0x60/0x10c [panfrost])
[58605.029430] [<bf00b54c>] (panfrost_gem_free_object [panfrost]) from [<bf00cecc>] (panfrost_job_put+0x138/0x150 [panfrost])
[58605.042076] [<bf00cecc>] (panfrost_job_put [panfrost]) from [<bf00121c>] (drm_sched_cleanup_jobs+0xc8/0xe0 [gpu_sched])
[58605.054417] [<bf00121c>] (drm_sched_cleanup_jobs [gpu_sched]) from [<bf001300>] (drm_sched_main+0xcc/0x26c [gpu_sched])
[58605.066620] [<bf001300>] (drm_sched_main [gpu_sched]) from [<c0146cfc>] (kthread+0x13c/0x154)
[58605.076226] [<c0146cfc>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
[58605.084346] Exception stack(0xe959bfb0 to 0xe959bff8)
[58605.090046] bfa0: 00000000 00000000 00000000 00000000
[58605.099250] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[58605.108480] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
[58605.116210] irq event stamp: 179
[58605.119955] hardirqs last enabled at (187): [<c017f7e4>] console_unlock+0x564/0x5c4
[58605.128935] hardirqs last disabled at (202): [<c017f308>] console_unlock+0x88/0x5c4
[58605.137788] softirqs last enabled at (216): [<c0102334>] __do_softirq+0x18c/0x548
[58605.146543] softirqs last disabled at (227): [<c0129528>] irq_exit+0xc4/0x10c
[58605.154618] ---[ end trace f65bdbd9ea9adfc0 ]---
----8<-----
The problem is that drm_sched_main() calls drm_sched_cleanup_jobs() as
part of the condition of wait_event_interruptible:
wait_event_interruptible(sched->wake_up_worker,
(drm_sched_cleanup_jobs(sched),
(!drm_sched_blocked(sched) &&
(entity = drm_sched_select_entity(sched))) ||
kthread_should_stop()));
When drm_sched_cleanup_jobs() is called *after* a wait (i.e. after
prepare_to_wait_event() has been called), then any might_sleep() will
moan loudly about it. This doesn't seem to happen often (I've only
triggered it once) because usually drm_sched_cleanup_jobs() either
doesn't sleep or does the sleeping during the first call that
wait_event_interruptible() makes (which is before the task state is set).
I don't really understand why drm_sched_cleanup_jobs() needs to be
called here, a simple change like below 'fixes' it. But I presume
there's some reason for the call being part of the
wait_event_interruptible condition. Can anyone shed light on this?
The code was introduced in commit 5918045c4ed4 ("drm/scheduler: rework job destruction")
Steve
----8<-----
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 9a0ee74d82dc..528f295e3a31 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -699,11 +699,12 @@ static int drm_sched_main(void *param)
struct drm_sched_job *sched_job;
struct dma_fence *fence;
+ drm_sched_cleanup_jobs(sched);
+
wait_event_interruptible(sched->wake_up_worker,
- (drm_sched_cleanup_jobs(sched),
(!drm_sched_blocked(sched) &&
(entity = drm_sched_select_entity(sched))) ||
- kthread_should_stop()));
+ kthread_should_stop());
if (!entity)
continue;
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