linux-kernel - [patch V3-2 11/51] posix-cpu-timers: Handle SIGEV_NONE timers correctly in timer

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Message-ID: <87wmmfyknh.ffs@tglx>
Date: Sun, 23 Jun 2024 13:16:02 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker
 <frederic@...nel.org>, John Stultz <jstultz@...gle.com>, Peter Zijlstra
 <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Stephen Boyd
 <sboyd@...nel.org>, Eric Biederman <ebiederm@...ssion.com>, Oleg Nesterov
 <oleg@...hat.com>
Subject: [patch V3-2 11/51] 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@...utronix.de>
---
V3-2: Fix the split up fallout - Frederic
V2: Split out into new patch to make review simpler - Frederic
---
 kernel/time/posix-cpu-timers.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

--- 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_itim
 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_
 				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;
 			}
 		}