There is a generic function __pvclock_read_cycles to be used to get both flags and cycles. For function pvclock_read_flags, it's useless to get cycles value. To make this function be more effective, add a new wrapper function to only get variable flags.
Signed-off-by: Minfei Huang <[email protected]> --- arch/x86/include/asm/pvclock.h | 12 ++++++++++++ arch/x86/kernel/pvclock.c | 3 +-- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h index 7c1c895..3c4e5b7 100644 --- a/arch/x86/include/asm/pvclock.h +++ b/arch/x86/include/asm/pvclock.h @@ -88,6 +88,18 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src, return version; } +static __always_inline unsigned int __pvclock_read_flags( + const struct pvclock_vcpu_time_info *src, u8 *flags) +{ + unsigned int version; + + version = src->version; + /* Make the latest version visible */ + smp_rmb(); + *flags = src->flags; + return version; +} + struct pvclock_vsyscall_time_info { struct pvclock_vcpu_time_info pvti; } __attribute__((__aligned__(SMP_CACHE_BYTES))); diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 7f82fe0..138772c 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -61,11 +61,10 @@ void pvclock_resume(void) u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) { unsigned version; - cycle_t ret; u8 flags; do { - version = __pvclock_read_cycles(src, &ret, &flags); + version = __pvclock_read_flags(src, &flags); /* Make sure that the version double-check is last. */ smp_rmb(); } while ((src->version & 1) || version != src->version); -- 2.6.3
