From 3aed64f6d341cdb62bb2d6232589fb13448ce063 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 9 Jun 2016 13:06:08 +0200 Subject: 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 --- arch/x86/entry/vdso/vclock_gettime.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) (limited to 'arch/x86/entry') 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 + -- cgit v1.2.3