commit 2ab516575f2f273b19d95140d02c54612201e80a
author Thomas Gleixner <tglx@linutronix.de> Tue Feb 28 19:46:04 2012 +0000
committer John Stultz <john.stultz@linaro.org> Thu Mar 15 18:17:58 2012 -0700
tree 26db92249e65754d99759af21fd207507a81cec8
parent 6c260d586343f7f78239d90aa9e2cfed02f74ff3

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>

arch/x86/vdso/vclock_gettime.c

diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 7eeb1f6..944c5e5 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -100,12 +100,12 @@
 	int mode;
 
 	do {
-		seq = read_seqbegin(&gtod->lock);
+		seq = read_seqcount_begin(&gtod->seq);
 		mode = gtod->clock.vclock_mode;
 		ts->tv_sec = gtod->wall_time_sec;
 		ts->tv_nsec = gtod->wall_time_nsec;
 		ns = vgetns();
-	} while (unlikely(read_seqretry(&gtod->lock, seq)));
+	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
 
 	timespec_add_ns(ts, ns);
 	return mode;
@@ -117,13 +117,13 @@
 	int mode;
 
 	do {
-		seq = read_seqbegin(&gtod->lock);
+		seq = read_seqcount_begin(&gtod->seq);
 		mode = gtod->clock.vclock_mode;
 		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(&gtod->lock, seq)));
+	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
 
 	/* wall_time_nsec, vgetns(), and wall_to_monotonic.tv_nsec
 	 * are all guaranteed to be nonnegative.
@@ -142,10 +142,10 @@
 {
 	unsigned long seq;
 	do {
-		seq = read_seqbegin(&gtod->lock);
+		seq = read_seqcount_begin(&gtod->seq);
 		ts->tv_sec = gtod->wall_time_coarse.tv_sec;
 		ts->tv_nsec = gtod->wall_time_coarse.tv_nsec;
-	} while (unlikely(read_seqretry(&gtod->lock, seq)));
+	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
 	return 0;
 }
 
@@ -153,12 +153,12 @@
 {
 	unsigned long seq, ns, secs;
 	do {
-		seq = read_seqbegin(&gtod->lock);
+		seq = read_seqcount_begin(&gtod->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(&gtod->lock, seq)));
+	} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
 
 	/* wall_time_nsec and wall_to_monotonic.tv_nsec are
 	 * guaranteed to be between 0 and NSEC_PER_SEC.