diff options
| -rw-r--r-- | fs/eventpoll.c | 114 |
1 files changed, 60 insertions, 54 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 68e27d1cb5cd..b42f53d64d11 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -381,7 +381,8 @@ static void ep_nested_calls_init(struct nested_calls *ncalls) */ static inline int ep_events_available(struct eventpoll *ep) { - return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; + return !list_empty_careful(&ep->rdllist) || + READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR; } #ifdef CONFIG_NET_RX_BUSY_POLL @@ -698,7 +699,7 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep, */ spin_lock_irq(&ep->wq.lock); list_splice_init(&ep->rdllist, &txlist); - ep->ovflist = NULL; + WRITE_ONCE(ep->ovflist, NULL); spin_unlock_irq(&ep->wq.lock); /* @@ -712,7 +713,7 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep, * other events might have been queued by the poll callback. * We re-insert them inside the main ready-list here. */ - for (nepi = ep->ovflist; (epi = nepi) != NULL; + for (nepi = READ_ONCE(ep->ovflist); (epi = nepi) != NULL; nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { /* * We need to check if the item is already in the list. @@ -730,7 +731,7 @@ static __poll_t ep_scan_ready_list(struct eventpoll *ep, * releasing the lock, events will be queued in the normal way inside * ep->rdllist. */ - ep->ovflist = EP_UNACTIVE_PTR; + WRITE_ONCE(ep->ovflist, EP_UNACTIVE_PTR); /* * Quickly re-inject items left on "txlist". @@ -1153,10 +1154,10 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v * semantics). All the events that happen during that period of time are * chained in ep->ovflist and requeued later on. */ - if (ep->ovflist != EP_UNACTIVE_PTR) { + if (READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR) { if (epi->next == EP_UNACTIVE_PTR) { - epi->next = ep->ovflist; - ep->ovflist = epi; + epi->next = READ_ONCE(ep->ovflist); + WRITE_ONCE(ep->ovflist, epi); if (epi->ws) { /* * Activate ep->ws since epi->ws may get @@ -1762,10 +1763,17 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, } else if (timeout == 0) { /* * Avoid the unnecessary trip to the wait queue loop, if the - * caller specified a non blocking operation. + * caller specified a non blocking operation. We still need + * lock because we could race and not see an epi being added + * to the ready list while in irq callback. Thus incorrectly + * returning 0 back to userspace. */ timed_out = 1; + spin_lock_irq(&ep->wq.lock); + eavail = ep_events_available(ep); + spin_unlock_irq(&ep->wq.lock); + goto check_events; } @@ -1774,64 +1782,62 @@ fetch_events: if (!ep_events_available(ep)) ep_busy_loop(ep, timed_out); + eavail = ep_events_available(ep); + if (eavail) + goto check_events; + + /* + * Busy poll timed out. Drop NAPI ID for now, we can add + * it back in when we have moved a socket with a valid NAPI + * ID onto the ready list. + */ + ep_reset_busy_poll_napi_id(ep); + + /* + * We don't have any available event to return to the caller. + * We need to sleep here, and we will be wake up by + * ep_poll_callback() when events will become available. + */ + init_waitqueue_entry(&wait, current); spin_lock_irq(&ep->wq.lock); + __add_wait_queue_exclusive(&ep->wq, &wait); + spin_unlock_irq(&ep->wq.lock); - if (!ep_events_available(ep)) { + for (;;) { /* - * Busy poll timed out. Drop NAPI ID for now, we can add - * it back in when we have moved a socket with a valid NAPI - * ID onto the ready list. + * We don't want to sleep if the ep_poll_callback() sends us + * a wakeup in between. That's why we set the task state + * to TASK_INTERRUPTIBLE before doing the checks. */ - ep_reset_busy_poll_napi_id(ep); - + set_current_state(TASK_INTERRUPTIBLE); /* - * We don't have any available event to return to the caller. - * We need to sleep here, and we will be wake up by - * ep_poll_callback() when events will become available. + * Always short-circuit for fatal signals to allow + * threads to make a timely exit without the chance of + * finding more events available and fetching + * repeatedly. */ - init_waitqueue_entry(&wait, current); - __add_wait_queue_exclusive(&ep->wq, &wait); - - for (;;) { - /* - * We don't want to sleep if the ep_poll_callback() sends us - * a wakeup in between. That's why we set the task state - * to TASK_INTERRUPTIBLE before doing the checks. - */ - set_current_state(TASK_INTERRUPTIBLE); - /* - * Always short-circuit for fatal signals to allow - * threads to make a timely exit without the chance of - * finding more events available and fetching - * repeatedly. - */ - if (fatal_signal_pending(current)) { - res = -EINTR; - break; - } - if (ep_events_available(ep) || timed_out) - break; - if (signal_pending(current)) { - res = -EINTR; - break; - } - - spin_unlock_irq(&ep->wq.lock); - if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) - timed_out = 1; - - spin_lock_irq(&ep->wq.lock); + if (fatal_signal_pending(current)) { + res = -EINTR; + break; + } + if (ep_events_available(ep) || timed_out) + break; + if (signal_pending(current)) { + res = -EINTR; + break; } - __remove_wait_queue(&ep->wq, &wait); - __set_current_state(TASK_RUNNING); + if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) + timed_out = 1; } -check_events: - /* Is it worth to try to dig for events ? */ - eavail = ep_events_available(ep); + __set_current_state(TASK_RUNNING); + + spin_lock_irq(&ep->wq.lock); + __remove_wait_queue(&ep->wq, &wait); spin_unlock_irq(&ep->wq.lock); +check_events: /* * Try to transfer events to user space. In case we get 0 events and * there's still timeout left over, we go trying again in search of |