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

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Message-ID: <20240610164026.162380808@linutronix.de>
Date: Mon, 10 Jun 2024 18:42:18 +0200 (CEST)
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 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>
---
V2: Split out into new patch to make review simpler - Frederic
---
 kernel/time/posix-cpu-timers.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -706,7 +706,16 @@ 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;
 			}
 		}