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| author | Paolo Bonzini <pbonzini@redhat.com> | 2016-06-09 13:06:08 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-08-04 13:52:21 +0200 |
| commit | 3aed64f6d341cdb62bb2d6232589fb13448ce063 (patch) | |
| tree | 33c7906993c84a861d4575a19a667bb5d8749046 /arch/x86/entry/vdso | |
| parent | 96b585267f552d4b6a28ea8bd75e5ed03deb6e71 (diff) | |
| download | linux-3aed64f6d341cdb62bb2d6232589fb13448ce063.tar.bz2 | |
pvclock: introduce seqcount-like API
The version field in struct pvclock_vcpu_time_info basically implements
a seqcount. Wrap it with the usual read_begin and read_retry functions,
and use these APIs instead of peppering the code with smp_rmb()s.
While at it, change it to the more pedantically correct virt_rmb().
With this change, __pvclock_read_cycles can be simplified noticeably.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/entry/vdso')
| -rw-r--r-- | arch/x86/entry/vdso/vclock_gettime.c | 9 |
1 files changed, 2 insertions, 7 deletions
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c index 2f02d23a05ef..db1e3b4c3693 100644 --- a/arch/x86/entry/vdso/vclock_gettime.c +++ b/arch/x86/entry/vdso/vclock_gettime.c @@ -123,9 +123,7 @@ static notrace cycle_t vread_pvclock(int *mode) */ do { - version = pvti->version; - - smp_rmb(); + version = pvclock_read_begin(pvti); if (unlikely(!(pvti->flags & PVCLOCK_TSC_STABLE_BIT))) { *mode = VCLOCK_NONE; @@ -137,10 +135,7 @@ static notrace cycle_t vread_pvclock(int *mode) pvti_tsc_shift = pvti->tsc_shift; pvti_system_time = pvti->system_time; pvti_tsc = pvti->tsc_timestamp; - - /* Make sure that the version double-check is last. */ - smp_rmb(); - } while (unlikely((version & 1) || version != pvti->version)); + } while (pvclock_read_retry(pvti, version)); delta = tsc - pvti_tsc; ret = pvti_system_time + |