tree 1c032ed0e7f61274484dcd13b7d73684649d3331
parent ea753d81e8b085d679f13e4a6023e003e9854d51
author Liu Ping Fan <qemulist@gmail.com> 1380090058 +0800
committer Paolo Bonzini <pbonzini@redhat.com> 1382023852 +0200

timer: protect timers_state's clock with seqlock

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>