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由 Eric Dumazet 提交于
Several crashes in cleanup_once() were reported in recent kernels. Commit d6cc1d64 (inetpeer: various changes) added a race in unlink_from_unused(). One way to avoid taking unused_peers.lock before doing the list_empty() test is to catch 0->1 refcnt transitions, using full barrier atomic operations variants (atomic_cmpxchg() and atomic_inc_return()) instead of previous atomic_inc() and atomic_add_unless() variants. We then call unlink_from_unused() only for the owner of the 0->1 transition. Add a new atomic_add_unless_return() static helper With help from Arun Sharma. Refs: https://bugzilla.kernel.org/show_bug.cgi?id=32772Reported-by: NArun Sharma <asharma@fb.com> Reported-by: NMaximilian Engelhardt <maxi@daemonizer.de> Reported-by: NYann Dupont <Yann.Dupont@univ-nantes.fr> Reported-by: NDenys Fedoryshchenko <denys@visp.net.lb> Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com> Signed-off-by: NDavid S. Miller <davem@davemloft.net>
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