cpu-timers: Change SIGEV_NONE timer implementation
When user sets up a timer without associated signal and process does
not use any other cpu timers and does not exit, tsk->signal->cputimer
is enabled and running forever.
Avoid running the timer for no reason.
I used below program to check patch does not break current user space
visible behavior.
#include <sys/time.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <assert.h>
void consume_cpu(void)
{
int i = 0;
int count = 0;
for(i=0; i<100000000; i++)
count++;
}
int main(void)
{
int i;
struct sigaction act;
struct sigevent evt = { };
timer_t tid;
struct itimerspec spec = { };
evt.sigev_notify = SIGEV_NONE;
assert(timer_create(CLOCK_PROCESS_CPUTIME_ID, &evt, &tid) == 0);
spec.it_value.tv_sec = 10;
assert(timer_settime(tid, 0, &spec, NULL) == 0);
for (i = 0; i < 30; i++) {
consume_cpu();
memset(&spec, 0, sizeof(spec));
assert(timer_gettime(tid, &spec) == 0);
printf("%lu.%09lu\n",
(unsigned long) spec.it_value.tv_sec,
(unsigned long) spec.it_value.tv_nsec);
}
assert(timer_delete(tid) == 0);
return 0;
}
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index cce2f0b..7d9d0fa 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -615,7 +615,12 @@
*/
static void cpu_timer_fire(struct k_itimer *timer)
{
- if (unlikely(timer->sigq == NULL)) {
+ if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
+ /*
+ * User don't want any signal.
+ */
+ timer->it.cpu.expires.sched = 0;
+ } else if (unlikely(timer->sigq == NULL)) {
/*
* This a special case for clock_nanosleep,
* not a normal timer from sys_timer_create.
@@ -784,7 +789,6 @@
*/
timer->it.cpu.expires = new_expires;
if (new_expires.sched != 0 &&
- (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
cpu_time_before(timer->it_clock, val, new_expires)) {
arm_timer(timer);
}
@@ -809,7 +813,6 @@
timer->it_overrun = -1;
if (new_expires.sched != 0 &&
- (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
!cpu_time_before(timer->it_clock, val, new_expires)) {
/*
* The designated time already passed, so we notify
@@ -883,25 +886,6 @@
read_unlock(&tasklist_lock);
}
- if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
- if (timer->it.cpu.incr.sched == 0 &&
- cpu_time_before(timer->it_clock,
- timer->it.cpu.expires, now)) {
- /*
- * Do-nothing timer expired and has no reload,
- * so it's as if it was never set.
- */
- timer->it.cpu.expires.sched = 0;
- itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
- return;
- }
- /*
- * Account for any expirations and reloads that should
- * have happened.
- */
- bump_cpu_timer(timer, now);
- }
-
if (unlikely(clear_dead)) {
/*
* We've noticed that the thread is dead, but
