Commit 8d1c98b0 authored by Davide Libenzi's avatar Davide Libenzi Committed by Linus Torvalds
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eventfd/kaio integration fix



Jeff Roberson discovered a race when using kaio eventfd based notifications.
When it occurs it can lead tomissed wakeups and hung userspace.

This patch fixes the race by moving the notification inside the spinlocked
section of kaio.  The operation is safe since eventfd spinlock and kaio one
are unrelated.
Signed-off-by: default avatarDavide Libenzi <davidel@xmailserver.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Jeff Roberson <jroberson@chesapeake.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d479540d
......@@ -936,14 +936,6 @@ int aio_complete(struct kiocb *iocb, long res, long res2)
return 1;
}
/*
* Check if the user asked us to deliver the result through an
* eventfd. The eventfd_signal() function is safe to be called
* from IRQ context.
*/
if (!IS_ERR(iocb->ki_eventfd))
eventfd_signal(iocb->ki_eventfd, 1);
info = &ctx->ring_info;
/* add a completion event to the ring buffer.
......@@ -992,6 +984,15 @@ int aio_complete(struct kiocb *iocb, long res, long res2)
kunmap_atomic(ring, KM_IRQ1);
pr_debug("added to ring %p at [%lu]\n", iocb, tail);
/*
* Check if the user asked us to deliver the result through an
* eventfd. The eventfd_signal() function is safe to be called
* from IRQ context.
*/
if (!IS_ERR(iocb->ki_eventfd))
eventfd_signal(iocb->ki_eventfd, 1);
put_rq:
/* everything turned out well, dispose of the aiocb. */
ret = __aio_put_req(ctx, iocb);
......
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