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timer: protect timers_state's clock with seqlock

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QEMU_CLOCK_VIRTUAL may be read outside BQL. This will make its
foundation, i.e. cpu_clock_offset exposed to race condition.
Using private lock to protect it.

After this patch, reading QEMU_CLOCK_VIRTUAL is thread safe
unless use_icount is true, in which case the existing callers
still rely on the BQL.

Lock rule: private lock innermost, ie BQL->"this lock"

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Liu Ping Fan 2013-09-25 14:20:58 +08:00 • committed by Paolo Bonzini
parent ea753d81e8
commit cb365646a9
2 changed files with 46 additions and 9 deletions
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2
include/qemu/timer.h
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@ -653,7 +653,9 @@ static inline int64_t qemu_soonest_timeout(int64_t timeout1, int64_t timeout2)
void init_clocks(void);
int64_t cpu_get_ticks(void);
/* Caller must hold BQL */
void cpu_enable_ticks(void);
/* Caller must hold BQL */
void cpu_disable_ticks(void);
static inline int64_t get_ticks_per_sec(void)