cgroup_event_wake() is called with hardirq-safe wqh->lock held, so the nested cgrp->event_list_lock should also be hardirq-safe.
Fortunately I don't think the deadlock can happen in real life. Lockdep never complained, maybe because it never found wqh->lock was held in irq context? Signed-off-by: Li Zefan <[email protected]> --- kernel/cgroup.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7a6c4c7..e72c44e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -3845,9 +3845,10 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode, struct cgroup_event *event = container_of(wait, struct cgroup_event, wait); struct cgroup *cgrp = event->cgrp; - unsigned long flags = (unsigned long)key; + unsigned long poll_flags = (unsigned long)key; + unsigned long flags; - if (flags & POLLHUP) { + if (poll_flags & POLLHUP) { /* * If the event has been detached at cgroup removal, we * can simply return knowing the other side will cleanup @@ -3857,7 +3858,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode, * side will require wqh->lock via remove_wait_queue(), * which we hold. */ - spin_lock(&cgrp->event_list_lock); + spin_lock_irqsave(&cgrp->event_list_lock, flags); if (!list_empty(&event->list)) { list_del_init(&event->list); /* @@ -3866,7 +3867,7 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode, */ schedule_work(&event->remove); } - spin_unlock(&cgrp->event_list_lock); + spin_unlock_irqrestore(&cgrp->event_list_lock, flags); } return 0; @@ -3981,9 +3982,9 @@ static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft, */ dget(cgrp->dentry); - spin_lock(&cgrp->event_list_lock); + spin_lock_irq(&cgrp->event_list_lock); list_add(&event->list, &cgrp->event_list); - spin_unlock(&cgrp->event_list_lock); + spin_unlock_irq(&cgrp->event_list_lock); fput(cfile); fput(efile); @@ -4406,12 +4407,12 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) * Notify userspace about cgroup removing only after rmdir of cgroup * directory to avoid race between userspace and kernelspace. */ - spin_lock(&cgrp->event_list_lock); + spin_lock_irq(&cgrp->event_list_lock); list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) { list_del_init(&event->list); schedule_work(&event->remove); } - spin_unlock(&cgrp->event_list_lock); + spin_unlock_irq(&cgrp->event_list_lock); return 0; } -- 1.8.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
