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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-11-25 15:31:39 +0300
committerIngo Molnar <mingo@elte.hu>2009-12-06 23:10:56 +0300
commit6ad4c18884e864cf4c77f9074d3d1816063f99cd (patch)
treef09643f6148b576fa2d23bf7d4b37d082d94e267 /include/linux/cpumask.h
parente1b8090bdf125f8b2e192149547fead7f302a89c (diff)
downloadlinux-6ad4c18884e864cf4c77f9074d3d1816063f99cd.tar.xz
sched: Fix balance vs hotplug race
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>
Diffstat (limited to 'include/linux/cpumask.h')
-rw-r--r--include/linux/cpumask.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 789cf5f920ce..d77b54733c5b 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)