From: Frederic Weisbecker <frederic@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Oleg Nesterov <oleg@redhat.com>
Subject: [PATCH 3/6] posix-cpu-timers: Force next expiration recalc after itimer reset
Date: Mon, 26 Jul 2021 14:55:10 +0200 [thread overview]
Message-ID: <20210726125513.271824-4-frederic@kernel.org> (raw)
In-Reply-To: <20210726125513.271824-1-frederic@kernel.org>
When an itimer deactivates a previously armed expiration, it simply
doesn't do anything. As a result the process wide cputime counter keeps
running and the tick dependency stays set until we reach the old
ghost expiration value.
This can be reproduced with the following snippet:
void trigger_process_counter(void)
{
struct itimerval n = {};
n.it_value.tv_sec = 100;
setitimer(ITIMER_VIRTUAL, &n, NULL);
n.it_value.tv_sec = 0;
setitimer(ITIMER_VIRTUAL, &n, NULL);
}
Fix this with resetting the relevant base expiration. This is similar
to disarming a timer.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
---
kernel/time/posix-cpu-timers.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 61c78b62fe6a..5c71322b45c7 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -1379,8 +1379,6 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
}
}
- if (!*newval)
- return;
*newval += now;
}
--
2.25.1
next prev parent reply other threads:[~2021-07-26 12:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-26 12:55 [GIT PULL] posix-cpu-timers leftover overhead fixes Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 1/6] posix-cpu-timers: Assert task sighand is locked while starting cputime counter Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 2/6] posix-cpu-timers: Force next_expiration recalc after timer deletion Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` Frederic Weisbecker [this message]
2021-08-10 15:13 ` [tip: timers/core] posix-cpu-timers: Force next expiration recalc after itimer reset tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 4/6] posix-cpu-timers: Remove confusing error code override Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] posix-cpu-timers: Remove confusing return value override tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 5/6] posix-cpu-timers: Consolidate timer base accessor Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
2021-07-26 12:55 ` [PATCH 6/6] posix-cpu-timers: Recalc next expiration when timer_settime() ends up not queueing Frederic Weisbecker
2021-08-10 15:13 ` [tip: timers/core] " tip-bot2 for Frederic Weisbecker
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