We observed the following hung task during our test: [ 3987.095999] INFO: task "kworker/u32:7":239 blocked for more than 188 seconds. [ 3987.096017] task:kworker/u32:7 state:D stack:0 pid:239 tgid:239 ppid:2 flags:0x00000408 [ 3987.096042] Workqueue: writeback wb_workfn (flush-254:59) [ 3987.096069] Call trace: [ 3987.096073] __switch_to+0x1a0/0x318 [ 3987.096089] __schedule+0xa38/0xf9c [ 3987.096104] schedule+0x74/0x10c [ 3987.096118] __bio_queue_enter+0xb8/0x178 [ 3987.096132] blk_mq_submit_bio+0x104/0x728 [ 3987.096145] __submit_bio+0xa0/0x23c [ 3987.096159] submit_bio_noacct_nocheck+0x164/0x330 [ 3987.096173] submit_bio_noacct+0x348/0x468 [ 3987.096186] submit_bio+0x17c/0x198 [ 3987.096199] f2fs_submit_write_bio+0x44/0xe8 [ 3987.096211] __submit_merged_bio+0x40/0x11c [ 3987.096222] __submit_merged_write_cond+0xcc/0x1f8 [ 3987.096233] f2fs_write_data_pages+0xbb8/0xd0c [ 3987.096246] do_writepages+0xe0/0x2f4 [ 3987.096255] __writeback_single_inode+0x44/0x4ac [ 3987.096272] writeback_sb_inodes+0x30c/0x538 [ 3987.096289] __writeback_inodes_wb+0x9c/0xec [ 3987.096305] wb_writeback+0x158/0x440 [ 3987.096321] wb_workfn+0x388/0x5d4 [ 3987.096335] process_scheduled_works+0x1c4/0x45c [ 3987.096346] worker_thread+0x32c/0x3e8 [ 3987.096356] kthread+0x11c/0x1b0 [ 3987.096372] ret_from_fork+0x10/0x20 T1: T2: blk_queue_enter blk_pm_resume_queue pm_request_resume __pm_runtime_resume(dev, RPM_ASYNC) rpm_resume __pm_runtime_disable dev->power.request_pending = true dev->power.disable_depth++ queue_work(pm_wq, &dev->power.work) __pm_runtime_barrier wait_event cancel_work_sync(&dev->power.work) T1 queues the work item, which is then cancelled by T2 before it starts execution. As a result, q->dev cannot be resumed, and T1 waits here for a long time. Signed-off-by: Yang Yang --- drivers/base/power/runtime.c | 3 ++- include/linux/pm.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 1b11a3cd4acc..fc9bf3fb3bb7 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -1533,7 +1533,8 @@ void __pm_runtime_disable(struct device *dev, bool check_resume) * means there probably is some I/O to process and disabling runtime PM * shouldn't prevent the device from processing the I/O. */ - if (check_resume && dev->power.request_pending && + if ((check_resume || dev->power.force_check_resume) && + dev->power.request_pending && dev->power.request == RPM_REQ_RESUME) { /* * Prevent suspends and idle notifications from being carried diff --git a/include/linux/pm.h b/include/linux/pm.h index cc7b2dc28574..4eb20569cdbc 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -708,6 +708,7 @@ struct dev_pm_info { bool use_autosuspend:1; bool timer_autosuspends:1; bool memalloc_noio:1; + bool force_check_resume:1; unsigned int links_count; enum rpm_request request; enum rpm_status runtime_status; -- 2.34.1