[tip:timers/core] posix-cpu-timers: Avoid timespec conversion in do_cpu_nanosleep()

[tip-bot for Thomas Gleixner <tipbot@xxxxxxxxx>]

Commit-ID:  343d8fc208e43e50525ae6e0fc4845b9966b7318
Gitweb:     http://git.kernel.org/tip/343d8fc208e43e50525ae6e0fc4845b9966b7318
Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 13 Jun 2017 23:29:14 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 14 Jun 2017 00:00:46 +0200

posix-cpu-timers: Avoid timespec conversion in do_cpu_nanosleep()

No point in converting the expiry time back and forth.

No point either to update the value in the caller supplied variable. mark
the rqtp argument const.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
 kernel/time/posix-cpu-timers.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 515148d..3adfa42 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1227,10 +1227,11 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
 }
 
 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
-			    struct timespec64 *rqtp)
+			    const struct timespec64 *rqtp)
 {
-	struct k_itimer timer;
 	struct itimerspec64 it;
+	struct k_itimer timer;
+	u64 expires;
 	int error;
 
 	/*
@@ -1279,7 +1280,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
 		/*
 		 * We were interrupted by a signal.
 		 */
-		*rqtp = ns_to_timespec64(timer.it.cpu.expires);
+		expires = timer.it.cpu.expires;
 		error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
 		if (!error) {
 			/*
@@ -1312,7 +1313,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
 		 * Report back to the user the time still remaining.
 		 */
 		restart = &current->restart_block;
-		restart->nanosleep.expires = timespec64_to_ns(rqtp);
+		restart->nanosleep.expires = expires;
 		if (restart->nanosleep.type != TT_NONE) {
 			struct timespec ts;
 
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