On 13-11-06 09:06 PM, Tiejun Chen wrote: > Commit 08c1ab68, "hotplug-use-migrate-disable.patch", intends to > use migrate_enable()/migrate_disable() to replace that combination Since you quote a commit ID, it would be nice if you mentioned that it is in v3.8-rt from the stable-rt repo, instead of making people look it up. Also, since you have cc'd stable-rt@vger, there should be some mention of what versions it might be appropriate for (3.4? 3.10?). > of preempt_enable() and preempt_disable(), but actually in > !CONFIG_PREEMPT_RT_FULL case, migrate_enable()/migrate_disable() > are still equal to preempt_enable()/preempt_disable(). So that > followed cpu_hotplug_begin()/cpu_unplug_begin(cpu) would go schedule() > to trigger schedule_debug() like this: > > _cpu_down() > | > + migrate_disable() = preempt_disable() > | > + cpu_hotplug_begin() or cpu_unplug_begin() > | > + schedule() > | > + __schedule() > | > + preempt_disable(); > | > + __schedule_bug() is true! > > So we should move migrate_enable() as the original scheme. It is unclear to me what context you are thinking of/referencing as the "original scheme"... > > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxxxxxx> > --- > kernel/cpu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 98f2ea3..da6e128 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -594,6 +594,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) > err = -EBUSY; > goto restore_cpus; > } > + migrate_enable(); > So, what happens if we now get migrated right here, before the hotplug_begin call below? P. -- > cpu_hotplug_begin(); > err = cpu_unplug_begin(cpu); > @@ -647,7 +648,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) > out_release: > cpu_unplug_done(cpu); > out_cancel: > - migrate_enable(); > cpu_hotplug_done(); > if (!err) > cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu); > -- To unsubscribe from this list: send the line "unsubscribe stable-rt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
