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authorEmilio G. Cota <cota@braap.org>2015-08-23 20:23:36 -0400
committerPaolo Bonzini <pbonzini@redhat.com>2015-09-07 18:12:39 +0200
commitd12f7309483e20d1bae9304f4b812bf53a8e6510 (patch)
treedcf0514e8f089dd8a0d610688f5e1e2435e8a6a9 /include/qemu
parent123fdbac9b8f1e394fbe92e8b5359193e94ba5bf (diff)
downloadhqemu-d12f7309483e20d1bae9304f4b812bf53a8e6510.zip
hqemu-d12f7309483e20d1bae9304f4b812bf53a8e6510.tar.gz
seqlock: read sequence number atomically
With this change we make sure that the compiler will not optimise the read of the sequence number in any way. Signed-off-by: Emilio G. Cota <cota@braap.org> Message-Id: <1440375847-17603-8-git-send-email-cota@braap.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include/qemu')
-rw-r--r--include/qemu/seqlock.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/qemu/seqlock.h b/include/qemu/seqlock.h
index f1256f5..70b01fd 100644
--- a/include/qemu/seqlock.h
+++ b/include/qemu/seqlock.h
@@ -55,18 +55,18 @@ static inline void seqlock_write_unlock(QemuSeqLock *sl)
static inline unsigned seqlock_read_begin(QemuSeqLock *sl)
{
/* Always fail if a write is in progress. */
- unsigned ret = sl->sequence & ~1;
+ unsigned ret = atomic_read(&sl->sequence);
/* Read sequence before reading other fields. */
smp_rmb();
- return ret;
+ return ret & ~1;
}
static inline int seqlock_read_retry(const QemuSeqLock *sl, unsigned start)
{
/* Read other fields before reading final sequence. */
smp_rmb();
- return unlikely(sl->sequence != start);
+ return unlikely(atomic_read(&sl->sequence) != start);
}
#endif
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