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.

Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>

1 files changed, 3 insertions, 8 deletions

diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 33385c18e5d..cdc95a707cd 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 = EMULATE;
 
@@ -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,