From: Thomas Gleixner 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 Signed-off-by: Andrew Morton --- kernel/itimer.c | 11 ++++++++++- 1 files changed, 10 insertions(+), 1 deletion(-) diff -puN kernel/itimer.c~hrtimers-fixup-itimer-conversion kernel/itimer.c --- devel/kernel/itimer.c~hrtimers-fixup-itimer-conversion 2006-01-19 20:11:18.000000000 -0800 +++ devel-akpm/kernel/itimer.c 2006-01-19 20:11:18.000000000 -0800 @@ -49,9 +49,11 @@ int do_getitimer(int which, struct itime 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 itime 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 itime 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); _