proc: mem_release() should check mm != NULL

[pandora-kernel.git] / fs / eventpoll.c

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index fe047d9..828e750 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -70,6 +70,15 @@
  * simultaneous inserts (A into B and B into A) from racing and
  * constructing a cycle without either insert observing that it is
  * going to.
+ * It is necessary 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.
  * It is possible to drop the "ep->mtx" and to use the global
  * mutex "epmutex" (together with "ep->lock") to have it working,
  * but having "ep->mtx" will make the interface more scalable.
@@ -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)
@@ -700,7 +711,7 @@ static const struct file_operations eventpoll_fops = {
        .llseek         = noop_llseek,
 };
 
-/* Fast test to see if the file is an evenpoll file */
+/* Fast test to see if the file is an eventpoll file */
 static inline int is_file_epoll(struct file *f)
 {
        return f->f_op == &eventpoll_fops;
@@ -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"