path: root/kernel
diff options
authorDmitry Adamushko <dmitry.adamushko@gmail.com>2008-07-30 12:34:04 +0200
committerIngo Molnar <mingo@elte.hu>2008-08-11 16:32:41 +0200
commit279ef6bbb8308488398c8f33b04c760148428378 (patch)
treebc2b925ce5ed3f943d57a2adc99324cf308712e7 /kernel
parent77ae651347bdd46830da8b28b1efc5e4a9d7cbd0 (diff)
sched, cpu hotplug: fix set_cpus_allowed() use in hotplug callbacks
Mark Langsdorf reported: > One of my co-workers noticed that the powernow-k8 > driver no longer restarts when a CPU core is > hot-disabled and then hot-enabled on AMD quad-core > systems. > > The following comands work fine on 2.6.26 and fail > on 2.6.27-rc1: > > echo 0 > /sys/devices/system/cpu/cpu3/online > echo 1 > /sys/devices/system/cpu/cpu3/online > find /sys -name cpufreq > > For 2.6.26, the find will return a cpufreq > directory for each processor. In 2.6.27-rc1, > the cpu3 directory is missing. > > After digging through the code, the following > logic is failing when the core is hot-enabled > at runtime. The code works during the boot > sequence. > > cpumask_t = current->cpus_allowed; > set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu)); > if (smp_processor_id() != cpu) > return -ENODEV; So set the CPU active before calling the CPU_ONLINE notifier chain, there are a handful of notifiers that use set_cpus_allowed(). This fix also solves the problem with x86-microcode. I've sent alternative patches for microcode, but as this "rely on set_cpus_allowed_ptr() being workable in cpu-hotplug(CPU_ONLINE, ...)" assumption seems to be more broad than what we thought, perhaps this fix should be applied. With this patch we define that by the moment CPU_ONLINE is being sent, a 'cpu' is online and ready for tasks to be migrated onto it. Signed-off-by: Dmitry Adamushko <dmitry.adamushko@gmail.com> Reported-by: Mark Langsdorf <mark.langsdorf@amd.com> Tested-by: Mark Langsdorf <mark.langsdorf@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
1 files changed, 2 insertions, 3 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c
index e202a68d1cc1..c977c339f559 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -349,6 +349,8 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
goto out_notify;
+ cpu_set(cpu, cpu_active_map);
/* Now call notifier in preparation. */
raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
@@ -383,9 +385,6 @@ int __cpuinit cpu_up(unsigned int cpu)
err = _cpu_up(cpu, 0);
- if (cpu_online(cpu))
- cpu_set(cpu, cpu_active_map);
return err;

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