Messages in this thread Patch in this message | | | From | Gregory Haskins <> | Subject | [PATCH 1/3] eventfd: Allow waiters to be notified about the eventfd file* going away | Date | Fri, 19 Jun 2009 14:51:27 -0400 |
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From: Davide Libenzi <davidel@xmailserver.org>
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 eventfd.
Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Tested-by: Gregory Haskins <ghaskins@novell.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Gregory Haskins <ghaskins@novell.com> Signed-off-by: Avi Kivity <avi@redhat.com> ---
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 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -59,7 +59,15 @@ int eventfd_signal(struct file *file, int n) static int eventfd_release(struct inode *inode, struct file *file) { - kfree(file->private_data); + 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); + kfree(ctx); return 0; }
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