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author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2010-03-24 18:34:10 +0100 |
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committer | Ingo Molnar <mingo@elte.hu> | 2010-04-02 20:12:03 +0200 |
commit | 0017d735092844118bef006696a750a0e4ef6ebd (patch) | |
tree | 8ed1540aaeb63da726f93da12950a8eaa0e0a3e0 /kernel/sched_idletask.c | |
parent | 9084bb8246ea935b98320554229e2f371f7f52fa (diff) | |
download | linux-0017d735092844118bef006696a750a0e4ef6ebd.tar.bz2 |
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_idletask.c')
-rw-r--r-- | kernel/sched_idletask.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c index a8a6d8a50947..5af709f503b0 100644 --- a/kernel/sched_idletask.c +++ b/kernel/sched_idletask.c @@ -6,7 +6,8 @@ */ #ifdef CONFIG_SMP -static int select_task_rq_idle(struct task_struct *p, int sd_flag, int flags) +static int +select_task_rq_idle(struct rq *rq, struct task_struct *p, int sd_flag, int flags) { return task_cpu(p); /* IDLE tasks as never migrated */ } |