[PATCH 1/3] eventfd: Allow waiters to be notified about the eventfdfile* going away
From: Gregory Haskins
Date: Fri Jun 19 2009 - 14:52:04 EST
From: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
And give them a change to unregister from the wait queue.
This is turn allows eventfd users to use the eventfd file* w/out holding a
live reference to it.
After the eventfd user callbacks returns, any usage of the eventfd file*
should be dropped. The eventfd user callback can acquire sleepy locks
since it is invoked lockless.
This is a feature, needed by KVM to avoid an awkward workaround when using
Signed-off-by: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Tested-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
fs/eventfd.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/fs/eventfd.c b/fs/eventfd.c
index 2a701d5..c71f51d 100644
@@ -59,7 +59,15 @@ int eventfd_signal(struct file *file, int n)
static int eventfd_release(struct inode *inode, struct file *file)
+ struct eventfd_ctx *ctx = file->private_data;
+ * No need to hold the lock here, since we are on the file cleanup
+ * path and the ones still attached to the wait queue will be
+ * serialized by wake_up_locked_poll().
+ wake_up_locked_poll(&ctx->wqh, POLLHUP);
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