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eventfd/kaio integration fix

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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: Davide Libenzi <davidel@xmailserver.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Jeff Roberson <jroberson@chesapeake.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davide Libenzi 2008-04-10 21:29:19 -07:00 committed by Linus Torvalds
parent d479540dba
commit 8d1c98b0b5
1 changed files with 9 additions and 8 deletions
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17
fs/aio.c
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@ -936,14 +936,6 @@ int aio_complete(struct kiocb *iocb, long res, long res2)
return 1; 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; info = &ctx->ring_info;
/* add a completion event to the ring buffer. /* 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); kunmap_atomic(ring, KM_IRQ1);
pr_debug("added to ring %p at [%lu]\n", iocb, tail); 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: put_rq:
/* everything turned out well, dispose of the aiocb. */ /* everything turned out well, dispose of the aiocb. */
ret = __aio_put_req(ctx, iocb); ret = __aio_put_req(ctx, iocb);