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Commit 8d1c98b0b5c0148b519c6416e689ef6a89ffcea3

Authored by Davide Libenzi
Committed by Linus Torvalds
1 parent d479540dba
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

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: 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>

Showing 1 changed file with 9 additions and 8 deletions Side-by-side Diff

... ... @@ -936,14 +936,6 @@
936 936 return 1;
937 937 }
938 938  
939   - /*
940   - * Check if the user asked us to deliver the result through an
941   - * eventfd. The eventfd_signal() function is safe to be called
942   - * from IRQ context.
943   - */
944   - if (!IS_ERR(iocb->ki_eventfd))
945   - eventfd_signal(iocb->ki_eventfd, 1);
946   -
947 939 info = &ctx->ring_info;
948 940  
949 941 /* add a completion event to the ring buffer.
... ... @@ -992,6 +984,15 @@
992 984 kunmap_atomic(ring, KM_IRQ1);
993 985  
994 986 pr_debug("added to ring %p at [%lu]\n", iocb, tail);
  987 +
  988 + /*
  989 + * Check if the user asked us to deliver the result through an
  990 + * eventfd. The eventfd_signal() function is safe to be called
  991 + * from IRQ context.
  992 + */
  993 + if (!IS_ERR(iocb->ki_eventfd))
  994 + eventfd_signal(iocb->ki_eventfd, 1);
  995 +
995 996 put_rq:
996 997 /* everything turned out well, dispose of the aiocb. */
997 998 ret = __aio_put_req(ctx, iocb);