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Will Deacon authored
commit 03110a5c upstream. Our futex implementation makes use of LDXR/STXR loops to perform atomic updates to user memory from atomic context. This can lead to latency problems if we end up spinning around the LL/SC sequence at the expense of doing something useful. Rework our futex atomic operations so that we return -EAGAIN if we fail to update the futex word after 128 attempts. The core futex code will reschedule if necessary and we'll try again later. Cc: <stable@kernel.org> Fixes: 6170a974 ("arm64: Atomic operations") Signed-off-by:
Will Deacon <will.deacon@arm.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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