diff options
Diffstat (limited to 'epoll-fix-spurious-lockdep-warnings.patch')
| -rw-r--r-- | epoll-fix-spurious-lockdep-warnings.patch | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/epoll-fix-spurious-lockdep-warnings.patch b/epoll-fix-spurious-lockdep-warnings.patch deleted file mode 100644 index 7ca77033e..000000000 --- a/epoll-fix-spurious-lockdep-warnings.patch +++ /dev/null @@ -1,119 +0,0 @@ -From: Nelson Elhage <nelhage@nelhage.com> -Subject: epoll: fix suprious lockdep warnings - -epoll can acquire multiple ep->mutex on multiple "struct eventpoll"s -at once in the case where one epoll fd is monitoring another epoll -fd. This is perfectly OK, since we're careful about the lock ordering, -but causes spurious lockdep warnings. Annotate the recursion using -mutex_lock_nested, and add a comment explaining the nesting rules for -good measure. - -Reported-by: Paul Bolle <pebolle@tiscali.nl> -Signed-off-by: Nelson Elhage <nelhage@nelhage.com> ---- - I've tested this on a synthetic epoll test case, that just adds e1 to - e2 and then does an epoll_wait(). I verified that it caused lockdep - problems on 3.0 and that this patch fixed it, but I haven't done more - extensive testing. Paul, are you able to test systemd against this? - - fs/eventpoll.c | 25 ++++++++++++++++++------- - 1 files changed, 18 insertions(+), 7 deletions(-) - -diff --git a/fs/eventpoll.c b/fs/eventpoll.c -index f9cfd16..0cb7bc6 100644 ---- a/fs/eventpoll.c -+++ b/fs/eventpoll.c -@@ -76,6 +76,15 @@ - * Events that require holding "epmutex" are very rare, while for - * normal operations the epoll private "ep->mtx" will guarantee - * a better scalability. -+ * It is possible to acquire multiple "ep->mtx"es at once in the case -+ * when one epoll fd is added to another. In this case, we always -+ * acquire the locks in the order of nesting (i.e. after epoll_ctl(e1, -+ * EPOLL_CTL_ADD, e2), e1->mtx will always be acquired before -+ * e2->mtx). Since we disallow cycles of epoll file descriptors, this -+ * ensures that the mutexes are well-ordered. In order to communicate -+ * this nesting to lockdep, when walking a tree of epoll file -+ * descriptors, we use the current recursion depth as the lockdep -+ * subkey. - */ - - /* Epoll private bits inside the event mask */ -@@ -464,13 +473,15 @@ static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) - * @ep: Pointer to the epoll private data structure. - * @sproc: Pointer to the scan callback. - * @priv: Private opaque data passed to the @sproc callback. -+ * @depth: The current depth of recursive f_op->poll calls. - * - * Returns: The same integer error code returned by the @sproc callback. - */ - static int ep_scan_ready_list(struct eventpoll *ep, - int (*sproc)(struct eventpoll *, - struct list_head *, void *), -- void *priv) -+ void *priv, -+ int depth) - { - int error, pwake = 0; - unsigned long flags; -@@ -481,7 +492,7 @@ static int ep_scan_ready_list(struct eventpoll *ep, - * We need to lock this because we could be hit by - * eventpoll_release_file() and epoll_ctl(). - */ -- mutex_lock(&ep->mtx); -+ mutex_lock_nested(&ep->mtx, depth); - - /* - * Steal the ready list, and re-init the original one to the -@@ -670,7 +681,7 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, - - static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) - { -- return ep_scan_ready_list(priv, ep_read_events_proc, NULL); -+ return ep_scan_ready_list(priv, ep_read_events_proc, NULL, call_nests + 1); - } - - static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) -@@ -737,7 +748,7 @@ void eventpoll_release_file(struct file *file) - - ep = epi->ep; - list_del_init(&epi->fllink); -- mutex_lock(&ep->mtx); -+ mutex_lock_nested(&ep->mtx, 0); - ep_remove(ep, epi); - mutex_unlock(&ep->mtx); - } -@@ -1134,7 +1145,7 @@ static int ep_send_events(struct eventpoll *ep, - esed.maxevents = maxevents; - esed.events = events; - -- return ep_scan_ready_list(ep, ep_send_events_proc, &esed); -+ return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0); - } - - static inline struct timespec ep_set_mstimeout(long ms) -@@ -1267,7 +1278,7 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) - struct rb_node *rbp; - struct epitem *epi; - -- mutex_lock(&ep->mtx); -+ mutex_lock_nested(&ep->mtx, call_nests + 1); - for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { - epi = rb_entry(rbp, struct epitem, rbn); - if (unlikely(is_file_epoll(epi->ffd.file))) { -@@ -1409,7 +1420,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, - } - - -- mutex_lock(&ep->mtx); -+ mutex_lock_nested(&ep->mtx, 0); - - /* - * Try to lookup the file inside our RB tree, Since we grabbed "mtx" --- -1.7.4.1 - --- -To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in -the body of a message to majordomo@vger.kernel.org -More majordomo info at http://vger.kernel.org/majordomo-info.html |