X-Git-Url: http://git.samba.org/samba.git/?a=blobdiff_plain;f=fs%2Feventpoll.c;h=a5d219d920e755aa7761253c87a1da6470f26782;hb=0fe4e2d5cd931ad2ff99d61cfdd5c6dc0c3ec60b;hp=8a5a1010886bad1f5c2918565807b5b3aaa988e1;hpb=115502a6f31d84d8172a71283aaea266302a8ad5;p=sfrench%2Fcifs-2.6.git diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 8a5a1010886b..a5d219d920e7 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 @@ -471,7 +472,6 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) * no re-entered. * * @ncalls: Pointer to the nested_calls structure to be used for this call. - * @max_nests: Maximum number of allowed nesting calls. * @nproc: Nested call core function pointer. * @priv: Opaque data to be passed to the @nproc callback. * @cookie: Cookie to be used to identify this nested call. @@ -480,7 +480,7 @@ static inline void ep_set_busy_poll_napi_id(struct epitem *epi) * Returns: Returns the code returned by the @nproc callback, or -1 if * the maximum recursion limit has been exceeded. */ -static int ep_call_nested(struct nested_calls *ncalls, int max_nests, +static int ep_call_nested(struct nested_calls *ncalls, int (*nproc)(void *, void *, int), void *priv, void *cookie, void *ctx) { @@ -499,7 +499,7 @@ static int ep_call_nested(struct nested_calls *ncalls, int max_nests, */ list_for_each_entry(tncur, lsthead, llink) { if (tncur->ctx == ctx && - (tncur->cookie == cookie || ++call_nests > max_nests)) { + (tncur->cookie == cookie || ++call_nests > EP_MAX_NESTS)) { /* * Ops ... loop detected or maximum nest level reached. * We abort this wake by breaking the cycle itself. @@ -573,7 +573,7 @@ static void ep_poll_safewake(wait_queue_head_t *wq) { int this_cpu = get_cpu(); - ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, + ep_call_nested(&poll_safewake_ncalls, ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); put_cpu(); @@ -699,7 +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); /* @@ -713,7 +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. @@ -731,7 +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". @@ -1154,10 +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 (unlikely(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 @@ -1333,7 +1333,6 @@ static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) } } else { error = ep_call_nested(&poll_loop_ncalls, - EP_MAX_NESTS, reverse_path_check_proc, child_file, child_file, current); @@ -1367,7 +1366,7 @@ static int reverse_path_check(void) /* let's call this for all tfiles */ list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { path_count_init(); - error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + error = ep_call_nested(&poll_loop_ncalls, reverse_path_check_proc, current_file, current_file, current); if (error) @@ -1626,21 +1625,24 @@ static __poll_t ep_send_events_proc(struct eventpoll *ep, struct list_head *head { struct ep_send_events_data *esed = priv; __poll_t revents; - struct epitem *epi; - struct epoll_event __user *uevent; + struct epitem *epi, *tmp; + struct epoll_event __user *uevent = esed->events; struct wakeup_source *ws; poll_table pt; init_poll_funcptr(&pt, NULL); + esed->res = 0; /* * We can loop without lock because we are passed a task private list. * Items cannot vanish during the loop because ep_scan_ready_list() is * holding "mtx" during this call. */ - for (esed->res = 0, uevent = esed->events; - !list_empty(head) && esed->res < esed->maxevents;) { - epi = list_first_entry(head, struct epitem, rdllink); + lockdep_assert_held(&ep->mtx); + + list_for_each_entry_safe(epi, tmp, head, rdllink) { + if (esed->res >= esed->maxevents) + break; /* * Activate ep->ws before deactivating epi->ws to prevent @@ -1660,42 +1662,42 @@ static __poll_t ep_send_events_proc(struct eventpoll *ep, struct list_head *head list_del_init(&epi->rdllink); - revents = ep_item_poll(epi, &pt, 1); - /* * If the event mask intersect the caller-requested one, * deliver the event to userspace. Again, ep_scan_ready_list() - * is holding "mtx", so no operations coming from userspace + * is holding ep->mtx, so no operations coming from userspace * can change the item. */ - if (revents) { - if (__put_user(revents, &uevent->events) || - __put_user(epi->event.data, &uevent->data)) { - list_add(&epi->rdllink, head); - ep_pm_stay_awake(epi); - if (!esed->res) - esed->res = -EFAULT; - return 0; - } - esed->res++; - uevent++; - if (epi->event.events & EPOLLONESHOT) - epi->event.events &= EP_PRIVATE_BITS; - else if (!(epi->event.events & EPOLLET)) { - /* - * If this file has been added with Level - * Trigger mode, we need to insert back inside - * the ready list, so that the next call to - * epoll_wait() will check again the events - * availability. At this point, no one can insert - * into ep->rdllist besides us. The epoll_ctl() - * callers are locked out by - * ep_scan_ready_list() holding "mtx" and the - * poll callback will queue them in ep->ovflist. - */ - list_add_tail(&epi->rdllink, &ep->rdllist); - ep_pm_stay_awake(epi); - } + revents = ep_item_poll(epi, &pt, 1); + if (!revents) + continue; + + if (__put_user(revents, &uevent->events) || + __put_user(epi->event.data, &uevent->data)) { + list_add(&epi->rdllink, head); + ep_pm_stay_awake(epi); + if (!esed->res) + esed->res = -EFAULT; + return 0; + } + esed->res++; + uevent++; + if (epi->event.events & EPOLLONESHOT) + epi->event.events &= EP_PRIVATE_BITS; + else if (!(epi->event.events & EPOLLET)) { + /* + * If this file has been added with Level + * Trigger mode, we need to insert back inside + * the ready list, so that the next call to + * epoll_wait() will check again the events + * availability. At this point, no one can insert + * into ep->rdllist besides us. The epoll_ctl() + * callers are locked out by + * ep_scan_ready_list() holding "mtx" and the + * poll callback will queue them in ep->ovflist. + */ + list_add_tail(&epi->rdllink, &ep->rdllist); + ep_pm_stay_awake(epi); } } @@ -1747,6 +1749,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, { int res = 0, eavail, timed_out = 0; u64 slack = 0; + bool waiter = false; wait_queue_entry_t wait; ktime_t expires, *to = NULL; @@ -1761,11 +1764,18 @@ 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); - goto check_events; + eavail = ep_events_available(ep); + spin_unlock_irq(&ep->wq.lock); + + goto send_events; } fetch_events: @@ -1773,64 +1783,66 @@ fetch_events: if (!ep_events_available(ep)) ep_busy_loop(ep, timed_out); - spin_lock_irq(&ep->wq.lock); + eavail = ep_events_available(ep); + if (eavail) + goto send_events; - if (!ep_events_available(ep)) { - /* - * 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); + /* + * 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. - */ + /* + * We don't have any available event to return to the caller. We need + * to sleep here, and we will be woken by ep_poll_callback() when events + * become available. + */ + if (!waiter) { + waiter = true; 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_lock_irq(&ep->wq.lock); + __add_wait_queue_exclusive(&ep->wq, &wait); + spin_unlock_irq(&ep->wq.lock); + } - spin_unlock_irq(&ep->wq.lock); - if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) - timed_out = 1; + 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; + } - spin_lock_irq(&ep->wq.lock); + eavail = ep_events_available(ep); + if (eavail) + 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; + break; + } } -check_events: - /* Is it worth to try to dig for events ? */ - eavail = ep_events_available(ep); - spin_unlock_irq(&ep->wq.lock); + __set_current_state(TASK_RUNNING); +send_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 @@ -1840,6 +1852,12 @@ check_events: !(res = ep_send_events(ep, events, maxevents)) && !timed_out) goto fetch_events; + if (waiter) { + spin_lock_irq(&ep->wq.lock); + __remove_wait_queue(&ep->wq, &wait); + spin_unlock_irq(&ep->wq.lock); + } + return res; } @@ -1876,7 +1894,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) ep_tovisit = epi->ffd.file->private_data; if (ep_tovisit->visited) continue; - error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + error = ep_call_nested(&poll_loop_ncalls, ep_loop_check_proc, epi->ffd.file, ep_tovisit, current); if (error != 0) @@ -1916,7 +1934,7 @@ static int ep_loop_check(struct eventpoll *ep, struct file *file) int ret; struct eventpoll *ep_cur, *ep_next; - ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, + ret = ep_call_nested(&poll_loop_ncalls, ep_loop_check_proc, file, ep, current); /* clear visited list */ list_for_each_entry_safe(ep_cur, ep_next, &visited_list, @@ -2172,7 +2190,7 @@ static int do_epoll_wait(int epfd, struct epoll_event __user *events, return -EINVAL; /* Verify that the area passed by the user is writeable */ - if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) + if (!access_ok(events, maxevents * sizeof(struct epoll_event))) return -EFAULT; /* Get the "struct file *" for the eventpoll file */