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author | Tejun Heo <tj@kernel.org> | 2010-05-06 18:49:21 +0200 |
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committer | Tejun Heo <tj@kernel.org> | 2010-05-06 18:49:21 +0200 |
commit | 94458d5ecb3da844823cc191e73e5c5ead98a464 (patch) | |
tree | 866f0ed3b4e522d98664cb4b2603cd0d34cfde0d /kernel/sched.c | |
parent | sched: replace migration_thread with cpu_stop (diff) | |
download | linux-94458d5ecb3da844823cc191e73e5c5ead98a464.tar.xz linux-94458d5ecb3da844823cc191e73e5c5ead98a464.zip |
sched: kill paranoia check in synchronize_sched_expedited()
The paranoid check which verifies that the cpu_stop callback is
actually called on all online cpus is completely superflous. It's
guaranteed by cpu_stop facility and if it didn't work as advertised
other things would go horribly wrong and trying to recover using
synchronize_sched() wouldn't be very meaningful.
Kill the paranoid check. Removal of this feature is done as a
separate step so that it can serve as a bisection point if something
actually goes wrong.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Cc: Josh Triplett <josh@freedesktop.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Dimitri Sivanich <sivanich@sgi.com>
Diffstat (limited to '')
-rw-r--r-- | kernel/sched.c | 40 |
1 files changed, 3 insertions, 37 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index f1d577a0a8ab..e9c6d798831a 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -8953,14 +8953,6 @@ static atomic_t synchronize_sched_expedited_count = ATOMIC_INIT(0); static int synchronize_sched_expedited_cpu_stop(void *data) { - static DEFINE_SPINLOCK(done_mask_lock); - struct cpumask *done_mask = data; - - if (done_mask) { - spin_lock(&done_mask_lock); - cpumask_set_cpu(smp_processor_id(), done_mask); - spin_unlock(&done_mask_lock); - } return 0; } @@ -8976,55 +8968,29 @@ static int synchronize_sched_expedited_cpu_stop(void *data) */ void synchronize_sched_expedited(void) { - cpumask_var_t done_mask_var; - struct cpumask *done_mask = NULL; int snap, trycount = 0; - /* - * done_mask is used to check that all cpus actually have - * finished running the stopper, which is guaranteed by - * stop_cpus() if it's called with cpu hotplug blocked. Keep - * the paranoia for now but it's best effort if cpumask is off - * stack. - */ - if (zalloc_cpumask_var(&done_mask_var, GFP_ATOMIC)) - done_mask = done_mask_var; - smp_mb(); /* ensure prior mod happens before capturing snap. */ snap = atomic_read(&synchronize_sched_expedited_count) + 1; get_online_cpus(); while (try_stop_cpus(cpu_online_mask, synchronize_sched_expedited_cpu_stop, - done_mask) == -EAGAIN) { + NULL) == -EAGAIN) { put_online_cpus(); if (trycount++ < 10) udelay(trycount * num_online_cpus()); else { synchronize_sched(); - goto free_out; + return; } if (atomic_read(&synchronize_sched_expedited_count) - snap > 0) { smp_mb(); /* ensure test happens before caller kfree */ - goto free_out; + return; } get_online_cpus(); } atomic_inc(&synchronize_sched_expedited_count); - if (done_mask) - cpumask_xor(done_mask, done_mask, cpu_online_mask); put_online_cpus(); - - /* paranoia - this can't happen */ - if (done_mask && cpumask_weight(done_mask)) { - char buf[80]; - - cpulist_scnprintf(buf, sizeof(buf), done_mask); - WARN_ONCE(1, "synchronize_sched_expedited: cpu online and done masks disagree on %d cpus: %s\n", - cpumask_weight(done_mask), buf); - synchronize_sched(); - } -free_out: - free_cpumask_var(done_mask_var); } EXPORT_SYMBOL_GPL(synchronize_sched_expedited); |