When CONFIG_PREEMPT_RT enable, raw_spin_lock() will preempt_disable() -> raw_spin_lock() -> wake_up() ... -> spin_lock_irqsave() which will trigger: BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 985654, name: iou-wrk-983605 preempt_count: 1, expected: 0 RCU nest depth: 0, expected: 0 CPU: 3 PID: 985654 Comm: iou-wrk-983605 Tainted: G O 6.1.83-rt28-g19631eb82f21 stack:0 ppid:977479 flags:0x00000008 tgid:977553 prio:120 preempt:0x100000001 rcu_read_lock_nesting:0 used_cpu 3 wake_cpu 3 on_cpu 3 on_rq 1 migrate_dis 0 arrive:17423426040675 queued:0 prev_sum:33955300 sum_exec:33955300 Call trace: dump_backtrace.part.0+0xdc/0xec show_stack+0x1c/0x30 dump_stack_lvl+0xac/0xc4 dump_stack+0x14/0x30 __might_resched+0x13c/0x170 rt_spin_lock+0x34/0xc0 __wake_up_common_lock+0x68/0xd0 __wake_up+0x1c/0x24 io_worker_handle_work+0x5b0/0x600 io_wqe_worker+0xf4/0x310 ret_from_fork+0x10/0x20 Signed-off-by: Xiaochuan Li --- Changes in v2: - Defer wake_up() after releasing acct->lock, add need_wake flag - Drop wq_has_sleeper() check, bare wake_up() is safe This is v2 of the previous submission. The v1 patch didn't show up on lore.kernel.org, no archived thread available. io_uring/io-wq: fix lockdep warning by deferring hash wake up outside acct->lock The stall wake up path in io_get_next_work() holds acct->lock while calling wake_up() on the hash wait queue, which creates lock ordering acct->lock -> hash->wait.lock and triggers lockdep circular dependency warning. The previous approach of temporarily dropping and retaking acct->lock is racy and juggles the lock unnecessarily. Instead, add a need_wake output flag to io_get_next_work() and defer the wake_up() to the outer worker loop, after acct->lock has been released. This preserves the calling convention that io_get_next_work() returns with acct->lock held, removes the lock inversion, and avoids any racy sleeper checks outside of the lock. Drop the wq_has_sleeper check as bare wake_up is safe and the optimization is not worth the complexity. io_uring/io-wq.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 2ca223e47d41..dbab506dd642 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -526,7 +526,8 @@ static bool io_wait_on_hash(struct io_wq *wq, unsigned int hash) } static struct io_wq_work *io_get_next_work(struct io_wq_acct *acct, - struct io_wq *wq) + struct io_wq *wq, + bool *need_wake) __must_hold(acct->lock) { struct io_wq_work_node *node, *prev; @@ -574,9 +575,8 @@ static struct io_wq_work *io_get_next_work(struct io_wq_acct *acct, unstalled = io_wait_on_hash(wq, stall_hash); raw_spin_lock(&acct->lock); if (unstalled) { + *need_wake = true; clear_bit(IO_ACCT_STALLED_BIT, &acct->flags); - if (wq_has_sleeper(&wq->hash->wait)) - wake_up(&wq->hash->wait); } } @@ -607,6 +607,7 @@ static void io_worker_handle_work(struct io_wq_acct *acct, do { struct io_wq_work *work; + bool need_wake = false; /* * If we got some work, mark us as busy. If we didn't, but @@ -615,7 +616,7 @@ static void io_worker_handle_work(struct io_wq_acct *acct, * can't make progress, any work completion or insertion will * clear the stalled flag. */ - work = io_get_next_work(acct, wq); + work = io_get_next_work(acct, wq, &need_wake); if (work) { /* * Make sure cancelation can find this, even before @@ -631,6 +632,9 @@ static void io_worker_handle_work(struct io_wq_acct *acct, raw_spin_unlock(&acct->lock); + if (need_wake) + wake_up(&wq->hash->wait); + if (!work) break; base-commit: a8c591ed6b672915e0be57843f943a2a723aff40 -- 2.43.0