[tip: timers/core] posix-cpu-timers: Handle SIGEV_NONE timers correctly in timer_set()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     5f9d4a1065949a64c107f93a89dc2b62f806c833
Gitweb:        https://git.kernel.org/tip/5f9d4a1065949a64c107f93a89dc2b62f806c833
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Sun, 23 Jun 2024 13:16:02 +02:00
Committer:     Frederic Weisbecker <frederic@xxxxxxxxxx>
CommitterDate: Mon, 29 Jul 2024 21:57:34 +02:00

posix-cpu-timers: Handle SIGEV_NONE timers correctly in timer_set()

Expired SIGEV_NONE oneshot timers must return 0 nsec for the expiry time in
timer_get(), but the posix CPU timer implementation returns 1 nsec.

Add the missing conditional.

This will be cleaned up in a follow up patch.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 kernel/time/posix-cpu-timers.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index d70879d..cf89044 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -623,6 +623,7 @@ static void cpu_timer_fire(struct k_itimer *timer)
 static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 			       struct itimerspec64 *new, struct itimerspec64 *old)
 {
+	bool sigev_none = timer->it_sigev_notify == SIGEV_NONE;
 	clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
 	u64 old_expires, new_expires, old_incr, val;
 	struct cpu_timer *ctmr = &timer->it.cpu;
@@ -706,7 +707,16 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 				old_expires = exp - val;
 				old->it_value = ns_to_timespec64(old_expires);
 			} else {
-				old->it_value.tv_nsec = 1;
+				/*
+				 * A single shot SIGEV_NONE timer must return 0, when it is
+				 * expired! Timers which have a real signal delivery mode
+				 * must return a remaining time greater than 0 because the
+				 * signal has not yet been delivered.
+				 */
+				if (sigev_none)
+					old->it_value.tv_nsec = 0;
+				else
+					old->it_value.tv_nsec = 1;
 				old->it_value.tv_sec = 0;
 			}
 		}