[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: George Anzinger <george@mvista.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>

[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: George Anzinger <george@mvista.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
George Anzinger · Linus Torvalds
1 parent b7343f01e3
Showing 1 changed file with 16 additions and 21 deletions Side-by-side Diff
kernel/itimer.c
@@ -112,28 +112,11 @@
 	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 @@
 	 * 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 @@
 		}
 		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);
...	...	@@ -112,28 +112,11 @@
112	112	return error;
113	113	}
114	114
115		-/*
116		- * Called with P->sighand->siglock held and P->signal->real_timer inactive.
117		- * If interval is nonzero, arm the timer for interval ticks from now.
118		- */
119		-static inline void it_real_arm(struct task_struct *p, unsigned long interval)
120		-{
121		- p->signal->it_real_value = interval; /* XXX unnecessary field?? */
122		- if (interval == 0)
123		- return;
124		- if (interval > (unsigned long) LONG_MAX)
125		- interval = LONG_MAX;
126		- /* the "+ 1" below makes sure that the timer doesn't go off before
127		- * the interval requested. This could happen if
128		- * time requested % (usecs per jiffy) is more than the usecs left
129		- * in the current jiffy */
130		- p->signal->real_timer.expires = jiffies + interval + 1;
131		- add_timer(&p->signal->real_timer);
132		-}
133	115
134	116	void it_real_fn(unsigned long __data)
135	117	{
136	118	struct task_struct * p = (struct task_struct *) __data;
	119	+ unsigned long inc = p->signal->it_real_incr;
137	120
138	121	send_group_sig_info(SIGALRM, SEND_SIG_PRIV, p);
139	122
140	123
141	124
...	...	@@ -141,14 +124,23 @@
141	124	* Now restart the timer if necessary. We don't need any locking
142	125	* here because do_setitimer makes sure we have finished running
143	126	* before it touches anything.
	127	+ * Note, we KNOW we are (or should be) at a jiffie edge here so
	128	+ * we don't need the +1 stuff. Also, we want to use the prior
	129	+ * expire value so as to not "slip" a jiffie if we are late.
	130	+ * Deal with requesting a time prior to "now" here rather than
	131	+ * in add_timer.
144	132	*/
145		- it_real_arm(p, p->signal->it_real_incr);
	133	+ if (!inc)
	134	+ return;
	135	+ while (time_before_eq(p->signal->real_timer.expires, jiffies))
	136	+ p->signal->real_timer.expires += inc;
	137	+ add_timer(&p->signal->real_timer);
146	138	}
147	139
148	140	int do_setitimer(int which, struct itimerval value, struct itimerval ovalue)
149	141	{
150	142	struct task_struct *tsk = current;
151		- unsigned long val, interval;
	143	+ unsigned long val, interval, expires;
152	144	cputime_t cval, cinterval, nval, ninterval;
153	145
154	146	switch (which) {
...	...	@@ -164,7 +156,10 @@
164	156	}
165	157	tsk->signal->it_real_incr =
166	158	timeval_to_jiffies(&value->it_interval);
167		- it_real_arm(tsk, timeval_to_jiffies(&value->it_value));
	159	+ expires = timeval_to_jiffies(&value->it_value);
	160	+ if (expires)
	161	+ mod_timer(&tsk->signal->real_timer,
	162	+ jiffies + 1 + expires);
168	163	spin_unlock_irq(&tsk->sighand->siglock);
169	164	if (ovalue) {
170	165	jiffies_to_timeval(val, &ovalue->it_value);