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 /include | |
| 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 'include')
| -rw-r--r-- | include/linux/cpumask.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index 789cf5f920c..d77b54733c5 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -84,6 +84,7 @@ extern const struct cpumask *const cpu_active_mask; #define num_online_cpus() cpumask_weight(cpu_online_mask) #define num_possible_cpus() cpumask_weight(cpu_possible_mask) #define num_present_cpus() cpumask_weight(cpu_present_mask) +#define num_active_cpus() cpumask_weight(cpu_active_mask) #define cpu_online(cpu) cpumask_test_cpu((cpu), cpu_online_mask) #define cpu_possible(cpu) cpumask_test_cpu((cpu), cpu_possible_mask) #define cpu_present(cpu) cpumask_test_cpu((cpu), cpu_present_mask) @@ -92,6 +93,7 @@ extern const struct cpumask *const cpu_active_mask; #define num_online_cpus() 1 #define num_possible_cpus() 1 #define num_present_cpus() 1 +#define num_active_cpus() 1 #define cpu_online(cpu) ((cpu) == 0) #define cpu_possible(cpu) ((cpu) == 0) #define cpu_present(cpu) ((cpu) == 0) |