[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>

1 files changed, 10 insertions, 1 deletions

diff --git a/kernel/itimer.c b/kernel/itimer.c
index c2c05c4ff28d..6433d0685506 100644
--- 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);