cpu-timers: Change SIGEV_NONE timer implementation (1f169f84) · Commits · 戴 / test

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>

kernel/posix-cpu-timers.c

+6 −22

Original line number	Diff line number	Diff line
		@@ -615,7 +615,12 @@ static void arm_timer(struct k_itimer *timer)
		*/
		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 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
		*/
		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 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
		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 @@ void posix_cpu_timer_get(struct k_itimer timer, struct itimerspec itp)
		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

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