[PATCH] hrtimers: fixup itimer conversion

The itimer conversion removed the locking which protects the timer and
variables in the shared signal structure.  Steven Rostedt found the problem in
the latest -rt patches.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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 c2c05c4..6433d06 100644 (file)
--- a/kernel/itimer.c
+++ b/kernel/itimer.c
@@ -49,9 +49,11 @@ int do_getitimer(int which, struct itimerval *value)
 
        switch (which) {
        case ITIMER_REAL:
+               spin_lock_irq(&tsk->sighand->siglock);
                value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
                value->it_interval =
                        ktime_to_timeval(tsk->signal->it_real_incr);
+               spin_unlock_irq(&tsk->sighand->siglock);
                break;
        case ITIMER_VIRTUAL:
                read_lock(&tasklist_lock);
@@ -150,8 +152,14 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 
        switch (which) {
        case ITIMER_REAL:
+again:
+               spin_lock_irq(&tsk->sighand->siglock);
                timer = &tsk->signal->real_timer;
-               hrtimer_cancel(timer);
+               /* We are sharing ->siglock with it_real_fn() */
+               if (hrtimer_try_to_cancel(timer) < 0) {
+                       spin_unlock_irq(&tsk->sighand->siglock);
+                       goto again;
+               }
                if (ovalue) {
                        ovalue->it_value = itimer_get_remtime(timer);
                        ovalue->it_interval
@@ -162,6 +170,7 @@ int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
                expires = timeval_to_ktime(value->it_value);
                if (expires.tv64 != 0)
                        hrtimer_start(timer, expires, HRTIMER_REL);
+               spin_unlock_irq(&tsk->sighand->siglock);
                break;
        case ITIMER_VIRTUAL:
                nval = timeval_to_cputime(&value->it_value);