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Commit d912d1ff authored by George Anzinger's avatar George Anzinger Committed by Linus Torvalds
Browse files

[PATCH] itimer fixes 



Fix the recent off-by-one fix in the itimer code:

1. The repeating timer is figured using the requested time
	(not +1 as we know where we are in the jiffie).

2. The tests for interval too large are left to the time_val to jiffie code.

Signed-off-by: default avatarGeorge Anzinger <george@mvista.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b7343f01

kernel/itimer.c

+16 −21
Original line number Diff line number Diff line
@@ -112,28 +112,11 @@ asmlinkage long sys_getitimer(int which, struct itimerval __user *value) 
	return error;

}



/*

 * Called with P->sighand->siglock held and P->signal->real_timer inactive.

 * If interval is nonzero, arm the timer for interval ticks from now.

 */

static inline void it_real_arm(struct task_struct *p, unsigned long interval)

{

	p->signal->it_real_value = interval; /* XXX unnecessary field?? */

	if (interval == 0)

		return;

	if (interval > (unsigned long) LONG_MAX)

		interval = LONG_MAX;

	/* the "+ 1" below makes sure that the timer doesn't go off before

	 * the interval requested. This could happen if

	 * time requested % (usecs per jiffy) is more than the usecs left

	 * in the current jiffy */

	p->signal->real_timer.expires = jiffies + interval + 1;

	add_timer(&p->signal->real_timer);

}



void it_real_fn(unsigned long __data)

{

	struct task_struct * p = (struct task_struct *) __data;

	unsigned long inc = p->signal->it_real_incr;



	send_group_sig_info(SIGALRM, SEND_SIG_PRIV, p);
@@ -141,14 +124,23 @@ void it_real_fn(unsigned long __data) 
	 * Now restart the timer if necessary.  We don't need any locking

	 * here because do_setitimer makes sure we have finished running

	 * before it touches anything.

	 * Note, we KNOW we are (or should be) at a jiffie edge here so

	 * we don't need the +1 stuff.  Also, we want to use the prior

	 * expire value so as to not "slip" a jiffie if we are late.

	 * Deal with requesting a time prior to "now" here rather than

	 * in add_timer.

	 */

	it_real_arm(p, p->signal->it_real_incr);

	if (!inc)

		return;

	while (time_before_eq(p->signal->real_timer.expires, jiffies))

		p->signal->real_timer.expires += inc;

	add_timer(&p->signal->real_timer);

}



int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)

{

	struct task_struct *tsk = current;

 	unsigned long val, interval;

 	unsigned long val, interval, expires;

	cputime_t cval, cinterval, nval, ninterval;



	switch (which) {
@@ -164,7 +156,10 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue) 
		}

		tsk->signal->it_real_incr =

			timeval_to_jiffies(&value->it_interval);

		it_real_arm(tsk, timeval_to_jiffies(&value->it_value));

		expires = timeval_to_jiffies(&value->it_value);

		if (expires)

			mod_timer(&tsk->signal->real_timer,

				  jiffies + 1 + expires);

		spin_unlock_irq(&tsk->sighand->siglock);

		if (ovalue) {

			jiffies_to_timeval(val, &ovalue->it_value);