[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>

diff --git a/kernel/itimer.c b/kernel/itimer.c
index a72cb0e..7c1b25e 100644 (file)
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -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 @@ again:
                }
                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);