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authorNelson Elhage <nelhage@nelhage.com>2011-11-01 00:13:14 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2011-11-01 00:30:57 (GMT)
commitd8805e633e054c816c47cb6e727c81f156d9253d (patch)
tree8f7151e635a38593d68eae40586449627d835965 /COPYING
parent15662b3e8644905032c2e26808401a487d4e90c1 (diff)
downloadlinux-d8805e633e054c816c47cb6e727c81f156d9253d.tar.xz
epoll: fix spurious lockdep warnings
epoll can acquire recursively acquire ep->mtx on multiple "struct eventpoll"s at once in the case where one epoll fd is monitoring another epoll fd. This is perfectly OK, since we're careful about the lock ordering, but it causes spurious lockdep warnings. Annotate the recursion using mutex_lock_nested, and add a comment explaining the nesting rules for good measure. Recent versions of systemd are triggering this, and it can also be demonstrated with the following trivial test program: --------------------8<-------------------- int main(void) { int e1, e2; struct epoll_event evt = { .events = EPOLLIN }; e1 = epoll_create1(0); e2 = epoll_create1(0); epoll_ctl(e1, EPOLL_CTL_ADD, e2, &evt); return 0; } --------------------8<-------------------- Reported-by: Paul Bolle <pebolle@tiscali.nl> Tested-by: Paul Bolle <pebolle@tiscali.nl> Signed-off-by: Nelson Elhage <nelhage@nelhage.com> Acked-by: Jason Baron <jbaron@redhat.com> Cc: Dave Jones <davej@redhat.com> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: <stable@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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