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.
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Eric W. Biederman <[email protected]>
---
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 13939f47c7b0..cc9f8be67694 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