| Message ID | 20241219093030.52080-1-tursulin@igalia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | workqueue: Do not warn when cancelling WQ_MEM_RECLAIM work from !WQ_MEM_RECLAIM worker | expand |
On Thu, Dec 19, 2024 at 09:30:30AM +0000, Tvrtko Ursulin wrote: > From: Tvrtko Ursulin <tvrtko.ursulin@igalia.com> > > After commit > 746ae46c1113 ("drm/sched: Mark scheduler work queues with WQ_MEM_RECLAIM") > amdgpu started seeing the following warning: > > [ ] workqueue: WQ_MEM_RECLAIM sdma0:drm_sched_run_job_work [gpu_sched] is flushing !WQ_MEM_RECLAIM events:amdgpu_device_delay_enable_gfx_off [amdgpu] > ... > [ ] Workqueue: sdma0 drm_sched_run_job_work [gpu_sched] > ... > [ ] Call Trace: > [ ] <TASK> > ... > [ ] ? check_flush_dependency+0xf5/0x110 > ... > [ ] cancel_delayed_work_sync+0x6e/0x80 > [ ] amdgpu_gfx_off_ctrl+0xab/0x140 [amdgpu] > [ ] amdgpu_ring_alloc+0x40/0x50 [amdgpu] > [ ] amdgpu_ib_schedule+0xf4/0x810 [amdgpu] > [ ] ? drm_sched_run_job_work+0x22c/0x430 [gpu_sched] > [ ] amdgpu_job_run+0xaa/0x1f0 [amdgpu] > [ ] drm_sched_run_job_work+0x257/0x430 [gpu_sched] > [ ] process_one_work+0x217/0x720 > ... > [ ] </TASK> > > The intent of the verifcation done in check_flush_depedency is to ensure > forward progress during memory reclaim, by flagging cases when either a > memory reclaim process, or a memory reclaim work item is flushed from a > context not marked as memory reclaim safe. > > This is correct when flushing, but when called from the > cancel(_delayed)_work_sync() paths it is a false positive because work is > either already running, or will not be running at all. Therefore > cancelling it is safe and we can relax the warning criteria by letting the > helper know of the calling context. > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com> > Fixes: fca839c00a12 ("workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue") > References: 746ae46c1113 ("drm/sched: Mark scheduler work queues with WQ_MEM_RECLAIM") > Cc: Tejun Heo <tj@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > Cc: Alex Deucher <alexander.deucher@amd.com> > Cc: Christian König <christian.koenig@amd.com > Cc: Matthew Brost <matthew.brost@intel.com> > Cc: <stable@vger.kernel.org> # v4.5+ Applied to wq/for-6.13-fixes. Thanks.
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 9949ffad8df0..7abba81296cd 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3680,23 +3680,27 @@ void workqueue_softirq_dead(unsigned int cpu) * check_flush_dependency - check for flush dependency sanity * @target_wq: workqueue being flushed * @target_work: work item being flushed (NULL for workqueue flushes) + * @from_cancel: are we called from the work cancel path * * %current is trying to flush the whole @target_wq or @target_work on it. - * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not - * reclaiming memory or running on a workqueue which doesn't have - * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to - * a deadlock. + * If this is not the cancel path (which implies work being flushed is either + * already running, or will not be at all), check if @target_wq doesn't have + * %WQ_MEM_RECLAIM and verify that %current is not reclaiming memory or running + * on a workqueue which doesn't have %WQ_MEM_RECLAIM as that can break forward- + * progress guarantee leading to a deadlock. */ static void check_flush_dependency(struct workqueue_struct *target_wq, - struct work_struct *target_work) + struct work_struct *target_work, + bool from_cancel) { - work_func_t target_func = target_work ? target_work->func : NULL; + work_func_t target_func; struct worker *worker; - if (target_wq->flags & WQ_MEM_RECLAIM) + if (from_cancel || target_wq->flags & WQ_MEM_RECLAIM) return; worker = current_wq_worker(); + target_func = target_work ? target_work->func : NULL; WARN_ONCE(current->flags & PF_MEMALLOC, "workqueue: PF_MEMALLOC task %d(%s) is flushing !WQ_MEM_RECLAIM %s:%ps", @@ -3966,7 +3970,7 @@ void __flush_workqueue(struct workqueue_struct *wq) list_add_tail(&this_flusher.list, &wq->flusher_overflow); } - check_flush_dependency(wq, NULL); + check_flush_dependency(wq, NULL, false); mutex_unlock(&wq->mutex); @@ -4141,7 +4145,7 @@ static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, } wq = pwq->wq; - check_flush_dependency(wq, work); + check_flush_dependency(wq, work, from_cancel); insert_wq_barrier(pwq, barr, work, worker); raw_spin_unlock_irq(&pool->lock);