TTY: switch tty_flip_buffer_push

[cascardo/linux.git] / fs / eventpoll.c

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index cd96649..9fec183 100644 (file)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -38,6 +38,8 @@
 #include <asm/io.h>
 #include <asm/mman.h>
 #include <linux/atomic.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 
 /*
  * LOCKING:
@@ -783,8 +785,34 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
        return pollflags != -1 ? pollflags : 0;
 }
 
+#ifdef CONFIG_PROC_FS
+static int ep_show_fdinfo(struct seq_file *m, struct file *f)
+{
+       struct eventpoll *ep = f->private_data;
+       struct rb_node *rbp;
+       int ret = 0;
+
+       mutex_lock(&ep->mtx);
+       for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+               struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
+
+               ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n",
+                                epi->ffd.fd, epi->event.events,
+                                (long long)epi->event.data);
+               if (ret)
+                       break;
+       }
+       mutex_unlock(&ep->mtx);
+
+       return ret;
+}
+#endif
+
 /* File callbacks that implement the eventpoll file behaviour */
 static const struct file_operations eventpoll_fops = {
+#ifdef CONFIG_PROC_FS
+       .show_fdinfo    = ep_show_fdinfo,
+#endif
        .release        = ep_eventpoll_release,
        .poll           = ep_eventpoll_poll,
        .llseek         = noop_llseek,
@@ -1285,7 +1313,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
         * otherwise we might miss an event that happens between the
         * f_op->poll() call and the new event set registering.
         */
-       epi->event.events = event->events;
+       epi->event.events = event->events; /* need barrier below */
        pt._key = event->events;
        epi->event.data = event->data; /* protected by mtx */
        if (epi->event.events & EPOLLWAKEUP) {
@@ -1295,6 +1323,26 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
                ep_destroy_wakeup_source(epi);
        }
 
+       /*
+        * The following barrier has two effects:
+        *
+        * 1) Flush epi changes above to other CPUs.  This ensures
+        *    we do not miss events from ep_poll_callback if an
+        *    event occurs immediately after we call f_op->poll().
+        *    We need this because we did not take ep->lock while
+        *    changing epi above (but ep_poll_callback does take
+        *    ep->lock).
+        *
+        * 2) We also need to ensure we do not miss _past_ events
+        *    when calling f_op->poll().  This barrier also
+        *    pairs with the barrier in wq_has_sleeper (see
+        *    comments for wq_has_sleeper).
+        *
+        * This barrier will now guarantee ep_poll_callback or f_op->poll
+        * (or both) will notice the readiness of an item.
+        */
+       smp_mb();
+
        /*
         * Get current event bits. We can safely use the file* here because
         * its usage count has been increased by the caller of this function.