diff options
| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-11-25 13:31:39 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-01-06 15:04:49 -0800 |
| commit | a09adfeb9ea89d22c301749a87480ac98edc2cce (patch) | |
| tree | 3416e3c66f940ed08bf18f41e4cb3212fb8638cd /kernel/cpuset.c | |
| parent | fb70ac4b23fc108eb92eef9434e111bbdd7fd922 (diff) | |
sched: Fix balance vs hotplug race
commit 6ad4c18884e864cf4c77f9074d3d1816063f99cd upstream.
Since (e761b77: cpu hotplug, sched: Introduce cpu_active_map and redo
sched domain managment) we have cpu_active_mask which is suppose to rule
scheduler migration and load-balancing, except it never (fully) did.
The particular problem being solved here is a crash in try_to_wake_up()
where select_task_rq() ends up selecting an offline cpu because
select_task_rq_fair() trusts the sched_domain tree to reflect the
current state of affairs, similarly select_task_rq_rt() trusts the
root_domain.
However, the sched_domains are updated from CPU_DEAD, which is after the
cpu is taken offline and after stop_machine is done. Therefore it can
race perfectly well with code assuming the domains are right.
Cure this by building the domains from cpu_active_mask on
CPU_DOWN_PREPARE.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel/cpuset.c')
| -rw-r--r-- | kernel/cpuset.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c index b5cb469d254..39e5121a78a 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -873,7 +873,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, if (retval < 0) return retval; - if (!cpumask_subset(trialcs->cpus_allowed, cpu_online_mask)) + if (!cpumask_subset(trialcs->cpus_allowed, cpu_active_mask)) return -EINVAL; } retval = validate_change(cs, trialcs); @@ -2011,7 +2011,7 @@ static void scan_for_empty_cpusets(struct cpuset *root) } /* Continue past cpusets with all cpus, mems online */ - if (cpumask_subset(cp->cpus_allowed, cpu_online_mask) && + if (cpumask_subset(cp->cpus_allowed, cpu_active_mask) && nodes_subset(cp->mems_allowed, node_states[N_HIGH_MEMORY])) continue; @@ -2020,7 +2020,7 @@ static void scan_for_empty_cpusets(struct cpuset *root) /* Remove offline cpus and mems from this cpuset. */ mutex_lock(&callback_mutex); cpumask_and(cp->cpus_allowed, cp->cpus_allowed, - cpu_online_mask); + cpu_active_mask); nodes_and(cp->mems_allowed, cp->mems_allowed, node_states[N_HIGH_MEMORY]); mutex_unlock(&callback_mutex); @@ -2058,8 +2058,10 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb, switch (phase) { case CPU_ONLINE: case CPU_ONLINE_FROZEN: - case CPU_DEAD: - case CPU_DEAD_FROZEN: + case CPU_DOWN_PREPARE: + case CPU_DOWN_PREPARE_FROZEN: + case CPU_DOWN_FAILED: + case CPU_DOWN_FAILED_FROZEN: break; default: @@ -2068,7 +2070,7 @@ static int cpuset_track_online_cpus(struct notifier_block *unused_nb, cgroup_lock(); mutex_lock(&callback_mutex); - cpumask_copy(top_cpuset.cpus_allowed, cpu_online_mask); + cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask); mutex_unlock(&callback_mutex); scan_for_empty_cpusets(&top_cpuset); ndoms = generate_sched_domains(&doms, &attr); @@ -2115,7 +2117,7 @@ static int cpuset_track_online_nodes(struct notifier_block *self, void __init cpuset_init_smp(void) { - cpumask_copy(top_cpuset.cpus_allowed, cpu_online_mask); + cpumask_copy(top_cpuset.cpus_allowed, cpu_active_mask); top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY]; hotcpu_notifier(cpuset_track_online_cpus, 0); |