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[Qemu-devel] [PATCH v3 05/15] seqlock: use atomic writes for the sequenc
From: |
Alex Bennée |
Subject: |
[Qemu-devel] [PATCH v3 05/15] seqlock: use atomic writes for the sequence |
Date: |
Fri, 30 Sep 2016 22:30:56 +0100 |
From: Paolo Bonzini <address@hidden>
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 <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Signed-off-by: Alex Bennée <address@hidden>
---
include/qemu/seqlock.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/qemu/seqlock.h b/include/qemu/seqlock.h
index 2e2be4c..8dee11d 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)
--
2.9.3
- [Qemu-devel] [PATCH v3 00/15] A number of fixes for ThreadSanitizer, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 01/15] atomic.h: fix __SANITIZE_THREAD__ build, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 03/15] exec-all.h: revert tb_page_addr_t to target_ulong, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 06/15] qom/object: update class cache atomically, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 02/15] atomic.h: comment on use of atomic_read/set, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 04/15] tcg/optimize: move default return out of if statement, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 10/15] linux-user/syscall: extend lock around cpu-list, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 05/15] seqlock: use atomic writes for the sequence,
Alex Bennée <=
- [Qemu-devel] [PATCH v3 08/15] cpu: atomically modify cpu->exit_request, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 07/15] qom/cpu: atomically clear the tb_jmp_cache, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 11/15] qga/command: use QEMU atomic primitives, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 12/15] .travis.yml: add gcc sanitizer build, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 13/15] tcg: ensure cpu_tb_exec/tb_gen_code use atomic_read/write, Alex Bennée, 2016/09/30
- [Qemu-devel] [PATCH v3 15/15] translate-all: mark updates to PageDesc as atomic, Alex Bennée, 2016/09/30