]> git.baikalelectronics.ru Git - kernel.git/commit
timer: Prevent base->clk from moving backward
authorFrederic Weisbecker <frederic@kernel.org>
Fri, 3 Jul 2020 01:06:57 +0000 (03:06 +0200)
committerThomas Gleixner <tglx@linutronix.de>
Thu, 9 Jul 2020 09:56:57 +0000 (11:56 +0200)
commit936f83c21296f74d6afcb88c74e69eb2c77dcc1c
tree1fc8c5174e08d76f9f7d7533c80face852479bb0
parent7952384771d28acf3a2e59e7e19595e6dca1c650
timer: Prevent base->clk from moving backward

When a timer is enqueued with a negative delta (ie: expiry is below
base->clk), it gets added to the wheel as expiring now (base->clk).

Yet the value that gets stored in base->next_expiry, while calling
trigger_dyntick_cpu(), is the initial timer->expires value. The
resulting state becomes:

base->next_expiry < base->clk

On the next timer enqueue, forward_timer_base() may accidentally
rewind base->clk. As a possible outcome, timers may expire way too
early, the worst case being that the highest wheel levels get spuriously
processed again.

To prevent from that, make sure that base->next_expiry doesn't get below
base->clk.

Fixes: f1b022ed11a7 ("timers: Forward the wheel clock whenever possible")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200703010657.2302-1-frederic@kernel.org
kernel/time/timer.c