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/kernel/pvclock.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-) (limited to 'arch/x86/kernel/pvclock.c') diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 06c58ce46762..3599404e3089 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -64,14 +64,9 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) u8 flags; do { - version = src->version; - /* Make the latest version visible */ - smp_rmb(); - + version = pvclock_read_begin(src); flags = src->flags; - /* Make sure that the version double-check is last. */ - smp_rmb(); - } while ((src->version & 1) || version != src->version); + } while (pvclock_read_retry(src, version)); return flags & valid_flags; } @@ -84,10 +79,10 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) u8 flags; do { - version = __pvclock_read_cycles(src, &ret, &flags); - /* Make sure that the version double-check is last. */ - smp_rmb(); - } while ((src->version & 1) || version != src->version); + version = pvclock_read_begin(src); + ret = __pvclock_read_cycles(src); + flags = src->flags; + } while (pvclock_read_retry(src, version)); if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { src->flags &= ~PVCLOCK_GUEST_STOPPED; -- cgit v1.2.3