From: Davidlohr Bueso <dave@xxxxxxxxxxxx> Subject: fs/epoll: loosen irq safety in epoll_insert() and epoll_remove() Both functions are similar to the context of ep_modify(), called via epoll_ctl(2). Just like ep_modify(), saving and restoring interrupts is an overkill in these calls as it will never be called with irqs disabled. While ep_remove() can be called directly from EPOLL_CTL_DEL, it can also be called when releasing the file, but this also complies with the above. Link: http://lkml.kernel.org/r/20180720172956.2883-3-dave@xxxxxxxxxxxx Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx> Cc: Jason Baron <jbaron@xxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/eventpoll.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) --- a/fs/eventpoll.c~fs-epoll-loosen-irq-safety-in-epoll_insert-and-epoll_remove +++ a/fs/eventpoll.c @@ -762,7 +762,6 @@ static void epi_rcu_free(struct rcu_head */ static int ep_remove(struct eventpoll *ep, struct epitem *epi) { - unsigned long flags; struct file *file = epi->ffd.file; /* @@ -777,10 +776,10 @@ static int ep_remove(struct eventpoll *e rb_erase_cached(&epi->rbn, &ep->rbr); - spin_lock_irqsave(&ep->wq.lock, flags); + spin_lock_irq(&ep->wq.lock); if (ep_is_linked(&epi->rdllink)) list_del_init(&epi->rdllink); - spin_unlock_irqrestore(&ep->wq.lock, flags); + spin_unlock_irq(&ep->wq.lock); wakeup_source_unregister(ep_wakeup_source(epi)); /* @@ -1409,7 +1408,6 @@ static int ep_insert(struct eventpoll *e { int error, pwake = 0; __poll_t revents; - unsigned long flags; long user_watches; struct epitem *epi; struct ep_pqueue epq; @@ -1476,7 +1474,7 @@ static int ep_insert(struct eventpoll *e goto error_remove_epi; /* We have to drop the new item inside our item list to keep track of it */ - spin_lock_irqsave(&ep->wq.lock, flags); + spin_lock_irq(&ep->wq.lock); /* record NAPI ID of new item if present */ ep_set_busy_poll_napi_id(epi); @@ -1493,7 +1491,7 @@ static int ep_insert(struct eventpoll *e pwake++; } - spin_unlock_irqrestore(&ep->wq.lock, flags); + spin_unlock_irq(&ep->wq.lock); atomic_long_inc(&ep->user->epoll_watches); @@ -1519,10 +1517,10 @@ error_unregister: * list, since that is used/cleaned only inside a section bound by "mtx". * And ep_insert() is called with "mtx" held. */ - spin_lock_irqsave(&ep->wq.lock, flags); + spin_lock_irq(&ep->wq.lock); if (ep_is_linked(&epi->rdllink)) list_del_init(&epi->rdllink); - spin_unlock_irqrestore(&ep->wq.lock, flags); + spin_unlock_irq(&ep->wq.lock); wakeup_source_unregister(ep_wakeup_source(epi)); _
