diff options
| author |   Andrew Morton <akpm@linux-foundation.org> | 2009-09-19 11:55:44 -0700 |
|---|---|---|
| committer |   Ingo Molnar <mingo@elte.hu> | 2009-09-20 20:00:32 +0200 |
| commit | 89f19f04dc72363d912fd007a399cb10310eff6e (patch) | |
| tree | daa64e5de98a668eed4a2ceeb6ca95c478be4053 /kernel | |
| parent | sched: Re-add lost cpu_allowed check to sched_fair.c::select_task_rq_fair() (diff) | |
| download | linux-dev-89f19f04dc72363d912fd007a399cb10310eff6e.tar.xz linux-dev-89f19f04dc72363d912fd007a399cb10310eff6e.zip | |
sched: Fix raciness in runqueue_is_locked()
runqueue_is_locked() is unavoidably racy due to a poor interface design.
It does
cpu = get_cpu()
ret = some_perpcu_thing(cpu);
put_cpu(cpu);
return ret;
Its return value is unreliable.
Fix.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <200909191855.n8JItiko022148@imap1.linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched.c | 10 | ||||
| -rw-r--r-- | kernel/trace/trace.c | 8 |
2 files changed, 9 insertions, 9 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index faf4d463bbff..575fb0139038 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -681,15 +681,9 @@ inline void update_rq_clock(struct rq *rq) * This interface allows printk to be called with the runqueue lock * held and know whether or not it is OK to wake up the klogd. */ -int runqueue_is_locked(void) +int runqueue_is_locked(int cpu) { - int cpu = get_cpu(); - struct rq *rq = cpu_rq(cpu); - int ret; - - ret = spin_is_locked(&rq->lock); - put_cpu(); - return ret; + return spin_is_locked(&cpu_rq(cpu)->lock); } /* diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index fd52a19dd172..420232a1fbba 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -275,12 +275,18 @@ static DEFINE_SPINLOCK(tracing_start_lock); */ void trace_wake_up(void) { + int cpu; + + if (trace_flags & TRACE_ITER_BLOCK) + return; /* * The runqueue_is_locked() can fail, but this is the best we * have for now: */ - if (!(trace_flags & TRACE_ITER_BLOCK) && !runqueue_is_locked()) + cpu = get_cpu(); + if (!runqueue_is_locked(cpu)) wake_up(&trace_wait); + put_cpu(); } static int __init set_buf_size(char *str) |