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| author | Paolo Bonzini <pbonzini@redhat.com> | 2016-09-30 22:30:56 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-10-04 10:00:26 +0200 |
| commit | f96a8cc3c633b25d9269337408ae2417ebbbad8e (patch) | |
| tree | 8d2f8fc029d7d988529bc0a4a2049d46b98cc045 | |
| parent | 550276ae0a88851edda2cb7fcdd64256dbb8e314 (diff) | |
| download | qemu-f96a8cc3c633b25d9269337408ae2417ebbbad8e.tar.gz | |
seqlock: use atomic writes for the sequence
There is a data race if the sequence is written concurrently to the
read. In C11 this has undefined behavior. Use atomic_set; the
read side is already using atomic_read.
Reported-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20160930213106.20186-6-alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | include/qemu/seqlock.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/qemu/seqlock.h b/include/qemu/seqlock.h index 2e2be4c4f0..8dee11d101 100644 --- a/include/qemu/seqlock.h +++ b/include/qemu/seqlock.h @@ -31,7 +31,7 @@ static inline void seqlock_init(QemuSeqLock *sl) /* Lock out other writers and update the count. */ static inline void seqlock_write_begin(QemuSeqLock *sl) { - ++sl->sequence; + atomic_set(&sl->sequence, sl->sequence + 1); /* Write sequence before updating other fields. */ smp_wmb(); @@ -42,7 +42,7 @@ static inline void seqlock_write_end(QemuSeqLock *sl) /* Write other fields before finalizing sequence. */ smp_wmb(); - ++sl->sequence; + atomic_set(&sl->sequence, sl->sequence + 1); } static inline unsigned seqlock_read_begin(QemuSeqLock *sl) |