From 80d136e138f59de35aafb0440e8ab2f51c40ccd5 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 19 Apr 2017 09:52:46 +0200 Subject: [PATCH] mm: make mm_percpu_wq non freezable Geert has reported a freeze during PM resume and some additional debugging has shown that the device_resume worker cannot make a forward progress because it waits for an event which is stuck waiting in drain_all_pages: INFO: task kworker/u4:0:5 blocked for more than 120 seconds. Not tainted 4.11.0-rc7-koelsch-00029-g005882e53d62f25d-dirty #3476 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:0 D 0 5 2 0x00000000 Workqueue: events_unbound async_run_entry_fn __schedule schedule schedule_timeout wait_for_common dpm_wait_for_superior device_resume async_resume async_run_entry_fn process_one_work worker_thread kthread [...] bash D 0 1703 1694 0x00000000 __schedule schedule schedule_timeout wait_for_common flush_work drain_all_pages start_isolate_page_range alloc_contig_range cma_alloc __alloc_from_contiguous cma_allocator_alloc __dma_alloc arm_dma_alloc sh_eth_ring_init sh_eth_open sh_eth_resume dpm_run_callback device_resume dpm_resume dpm_resume_end suspend_devices_and_enter pm_suspend state_store kernfs_fop_write __vfs_write vfs_write SyS_write [...] Showing busy workqueues and worker pools: [...] workqueue mm_percpu_wq: flags=0xc pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=0/0 delayed: drain_local_pages_wq, vmstat_update pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=0/0 delayed: drain_local_pages_wq BAR(1703), vmstat_update Tetsuo has properly noted that mm_percpu_wq is created as WQ_FREEZABLE so it is frozen this early during resume so we are effectively deadlocked. Fix this by dropping WQ_FREEZABLE when creating mm_percpu_wq. We really want to have it operational all the time. Fixes: ce612879ddc7 ("mm: move pcp and lru-pcp draining into single wq") Reported-and-tested-by: Geert Uytterhoeven Debugged-by: Tetsuo Handa Signed-off-by: Michal Hocko Signed-off-by: Linus Torvalds --- mm/vmstat.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index 809025e..5a4f5c5 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1768,8 +1768,7 @@ void __init init_mm_internals(void) { int ret __maybe_unused; - mm_percpu_wq = alloc_workqueue("mm_percpu_wq", - WQ_FREEZABLE|WQ_MEM_RECLAIM, 0); + mm_percpu_wq = alloc_workqueue("mm_percpu_wq", WQ_MEM_RECLAIM, 0); #ifdef CONFIG_SMP ret = cpuhp_setup_state_nocalls(CPUHP_MM_VMSTAT_DEAD, "mm/vmstat:dead", -- 2.7.4