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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2010-03-24 18:34:10 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2010-04-02 20:12:03 +0200 |
| commit | 0017d735092844118bef006696a750a0e4ef6ebd (patch) | |
| tree | 8ed1540aaeb63da726f93da12950a8eaa0e0a3e0 /kernel/sched_fair.c | |
| parent | sched: Make select_fallback_rq() cpuset friendly (diff) | |
| download | linux-0017d735092844118bef006696a750a0e4ef6ebd.tar.xz linux-0017d735092844118bef006696a750a0e4ef6ebd.zip | |
sched: Fix TASK_WAKING vs fork deadlock
Oleg noticed a few races with the TASK_WAKING usage on fork.
- since TASK_WAKING is basically a spinlock, it should be IRQ safe
- since we set TASK_WAKING (*) without holding rq->lock it could
be there still is a rq->lock holder, thereby not actually
providing full serialization.
(*) in fact we clear PF_STARTING, which in effect enables TASK_WAKING.
Cure the second issue by not setting TASK_WAKING in sched_fork(), but
only temporarily in wake_up_new_task() while calling select_task_rq().
Cure the first by holding rq->lock around the select_task_rq() call,
this will disable IRQs, this however requires that we push down the
rq->lock release into select_task_rq_fair()'s cgroup stuff.
Because select_task_rq_fair() still needs to drop the rq->lock we
cannot fully get rid of TASK_WAKING.
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
| -rw-r--r-- | kernel/sched_fair.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 49ad99378f82..8a5e7632d09b 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1423,7 +1423,8 @@ select_idle_sibling(struct task_struct *p, struct sched_domain *sd, int target) * * preempt must be disabled. */ -static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) +static int +select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_flags) { struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; int cpu = smp_processor_id(); @@ -1521,8 +1522,11 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag cpumask_weight(sched_domain_span(sd)))) tmp = affine_sd; - if (tmp) + if (tmp) { + raw_spin_unlock(&rq->lock); update_shares(tmp); + raw_spin_lock(&rq->lock); + } } #endif |