From 9a3062e6c8b8a2ab2f5a92db68627a6d8f611f3a Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 28 Feb 2012 18:24:07 +0100 Subject: [PATCH 018/293] x86: vdso: Use seqcount instead of seqlock The update of the vdso data happens under xtime_lock, so adding a nested lock is pointless. Just use a seqcount to sync the readers. Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/vgtod.h | 2 +- arch/x86/kernel/vsyscall_64.c | 11 +++-------- arch/x86/vdso/vclock_gettime.c | 16 ++++++++-------- 3 files changed, 12 insertions(+), 17 deletions(-) diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h index 815285b..1f00717 100644 --- a/arch/x86/include/asm/vgtod.h +++ b/arch/x86/include/asm/vgtod.h @@ -5,7 +5,7 @@ #include struct vsyscall_gtod_data { - seqlock_t lock; + seqcount_t seq; /* open coded 'struct timespec' */ time_t wall_time_sec; diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index f04adbd..50392ee 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -52,10 +52,7 @@ #include "vsyscall_trace.h" DEFINE_VVAR(int, vgetcpu_mode); -DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) = -{ - .lock = __SEQLOCK_UNLOCKED(__vsyscall_gtod_data.lock), -}; +DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data); static enum { EMULATE, NATIVE, NONE } vsyscall_mode = NATIVE; @@ -86,9 +83,7 @@ void update_vsyscall_tz(void) void update_vsyscall(struct timespec *wall_time, struct timespec *wtm, struct clocksource *clock, u32 mult) { - unsigned long flags; - - write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags); + write_seqcount_begin(&vsyscall_gtod_data.seq); /* copy vsyscall data */ vsyscall_gtod_data.clock.vclock_mode = clock->archdata.vclock_mode; @@ -101,7 +96,7 @@ void update_vsyscall(struct timespec *wall_time, struct timespec *wtm, vsyscall_gtod_data.wall_to_monotonic = *wtm; vsyscall_gtod_data.wall_time_coarse = __current_kernel_time(); - write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags); + write_seqcount_end(&vsyscall_gtod_data.seq); } static void warn_bad_vsyscall(const char *level, struct pt_regs *regs, diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index 6bc0e72..d8511fb 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -86,11 +86,11 @@ notrace static noinline int do_realtime(struct timespec *ts) { unsigned long seq, ns; do { - seq = read_seqbegin(>od->lock); + seq = read_seqcount_begin(>od->seq); ts->tv_sec = gtod->wall_time_sec; ts->tv_nsec = gtod->wall_time_nsec; ns = vgetns(); - } while (unlikely(read_seqretry(>od->lock, seq))); + } while (unlikely(read_seqcount_retry(>od->seq, seq))); timespec_add_ns(ts, ns); return 0; } @@ -99,12 +99,12 @@ notrace static noinline int do_monotonic(struct timespec *ts) { unsigned long seq, ns, secs; do { - seq = read_seqbegin(>od->lock); + seq = read_seqcount_begin(>od->seq); secs = gtod->wall_time_sec; ns = gtod->wall_time_nsec + vgetns(); secs += gtod->wall_to_monotonic.tv_sec; ns += gtod->wall_to_monotonic.tv_nsec; - } while (unlikely(read_seqretry(>od->lock, seq))); + } while (unlikely(read_seqcount_retry(>od->seq, seq))); /* wall_time_nsec, vgetns(), and wall_to_monotonic.tv_nsec * are all guaranteed to be nonnegative. @@ -123,10 +123,10 @@ notrace static noinline int do_realtime_coarse(struct timespec *ts) { unsigned long seq; do { - seq = read_seqbegin(>od->lock); + seq = read_seqcount_begin(>od->seq); ts->tv_sec = gtod->wall_time_coarse.tv_sec; ts->tv_nsec = gtod->wall_time_coarse.tv_nsec; - } while (unlikely(read_seqretry(>od->lock, seq))); + } while (unlikely(read_seqcount_retry(>od->seq, seq))); return 0; } @@ -134,12 +134,12 @@ notrace static noinline int do_monotonic_coarse(struct timespec *ts) { unsigned long seq, ns, secs; do { - seq = read_seqbegin(>od->lock); + seq = read_seqcount_begin(>od->seq); secs = gtod->wall_time_coarse.tv_sec; ns = gtod->wall_time_coarse.tv_nsec; secs += gtod->wall_to_monotonic.tv_sec; ns += gtod->wall_to_monotonic.tv_nsec; - } while (unlikely(read_seqretry(>od->lock, seq))); + } while (unlikely(read_seqcount_retry(>od->seq, seq))); /* wall_time_nsec and wall_to_monotonic.tv_nsec are * guaranteed to be between 0 and NSEC_PER_SEC.