From: Davide Libenzi <davidel@xmailserver.org>
Date: Fri, 17 Oct 2008 23:17:40 +0000 (-0700)
Subject: epoll: avoid double-inserts in case of EFAULT
X-Git-Tag: v2.6.28-rc2~2
X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=9ce209d64d820a6d5ed6b952e2c0f917faad6031;hp=9ce209d64d820a6d5ed6b952e2c0f917faad6031;p=linux-2.6-omap-h63xx.git

epoll: avoid double-inserts in case of EFAULT

In commit f337b9c58332bdecde965b436e47ea4c94d30da0 ("epoll: drop
unnecessary test") Thomas found that there is an unnecessary (always
true) test in ep_send_events().  The callback never inserts into
->rdllink while the send loop is performed, and also does the
~EP_PRIVATE_BITS test.  Given we're holding the mutex during this time,
the conditions tested inside the loop are always true.

HOWEVER.

The test "!ep_is_linked(&epi->rdllink)" wasn't there because we insert
into ->rdllink, but because the send-events loop might terminate before
the whole list is scanned (-EFAULT).

In such cases, when the loop terminates early, and when a (leftover)
file received an event while we're performing the lockless loop, we need
such test to avoid to double insert the epoll items.  The list_splice()
done a few steps below, will correctly re-insert the ones that were left
on "txlist".

This should fix the kenrel.org bugzilla entry 11831.

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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