Prev: [PATCH 1/5] sched: __sched_setscheduler: read RLIMIT_RTPRIO lockless
Next: Dear Account Owner,
From: Oleg Nesterov on 10 Jun 2010 19:20
run_posix_cpu_timers() doesn't work if current has already passed
exit_notify(). This was needed to prevent the races with do_wait().

Since ea6d290c ->signal is always valid and can't go away. We can
remove the "tsk->exit_state == 0" in fastpath_timer_check() and
convert run_posix_cpu_timers() to use lock_task_sighand().

Note: it makes sense to take group_leader's sighand instead, the
sub-thread still uses CPU after release_task(). But we need more
changes to do this.

Signed-off-by: Oleg Nesterov <oleg(a)redhat.com>
---

kernel/posix-cpu-timers.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

--- 35-rc2/kernel/posix-cpu-timers.c~5_RUN_PCT_DONT_CK_EXIT_STATE 2010-06-11 01:07:48.000000000 +0200
+++ 35-rc2/kernel/posix-cpu-timers.c 2010-06-11 01:08:03.000000000 +0200
@@ -1272,10 +1272,6 @@ static inline int fastpath_timer_check(s
{
struct signal_struct *sig;

- /* tsk == current, ensure it is safe to use ->signal/sighand */
- if (unlikely(tsk->exit_state))
- return 0;
-
if (!task_cputime_zero(&tsk->cputime_expires)) {
struct task_cputime task_sample = {
.utime = tsk->utime,
@@ -1308,6 +1304,7 @@ void run_posix_cpu_timers(struct task_st
{
LIST_HEAD(firing);
struct k_itimer *timer, *next;
+ unsigned long flags;

BUG_ON(!irqs_disabled());

@@ -1318,7 +1315,8 @@ void run_posix_cpu_timers(struct task_st
if (!fastpath_timer_check(tsk))
return;

- spin_lock(&tsk->sighand->siglock);
+ if (!lock_task_sighand(tsk, &flags))
+ return;
/*
* Here we take off tsk->signal->cpu_timers[N] and
* tsk->cpu_timers[N] all the timers that are firing, and
@@ -1340,7 +1338,7 @@ void run_posix_cpu_timers(struct task_st
* that gets the timer lock before we do will give it up and
* spin until we've taken care of that timer below.
*/
- spin_unlock(&tsk->sighand->siglock);
+ unlock_task_sighand(tsk, &flags);

/*
* Now that all the timers on our list have the firing flag,

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
 | 
Pages: 1
Prev: [PATCH 1/5] sched: __sched_setscheduler: read RLIMIT_RTPRIO lockless
Next: Dear Account Owner,