On 09/14/2013 12:43 PM, Wang YanQing wrote:
> On Sat, Sep 14, 2013 at 12:41:36PM +0800, Wang YanQing wrote:
>> On Thu, Sep 12, 2013 at 12:07:05AM +0800, Jiang Liu wrote:
>>> From: Jiang Liu <jiang.liu@xxxxxxxxxx>
>>>
>>> Commit f44310b98ddb7 "smp: Fix SMP function call empty cpu mask race"
>>> introduced field call_function_data->cpumask_ipi to resolve a race
>>> condition in smp_call_function_many().
>>>
>>> Later commit 9a46ad6d6df3 "smp: make smp_call_function_many() use logic
>>> similar to smp_call_function_single()" fixed the same issue in another
>>> way when optimizing smp_call_function_many(), which then obsoletes
>>> changes introduced by commit f44310b98ddb7. So revert it.
>>>
>>> Signed-off-by: Jiang Liu <jiang.liu@xxxxxxxxxx>
>>> Acked-by: Wang YanQing <udknight@xxxxxxxxx>
>>> Cc: Jiang Liu <liuj97@xxxxxxxxx>
>>> ---
>>> kernel/smp.c | 16 ++--------------
>>> 1 file changed, 2 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/kernel/smp.c b/kernel/smp.c
>>> index fe9f773..a034712 100644
>>> --- a/kernel/smp.c
>>> +++ b/kernel/smp.c
>>> @@ -23,7 +23,6 @@ enum {
>>> struct call_function_data {
>>> struct call_single_data __percpu *csd;
>>> cpumask_var_t cpumask;
>>> - cpumask_var_t cpumask_ipi;
>>> };
>>>
>>> static DEFINE_PER_CPU_SHARED_ALIGNED(struct call_function_data, cfd_data);
>>> @@ -47,9 +46,6 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
>>> if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
>>> cpu_to_node(cpu)))
>>> return notifier_from_errno(-ENOMEM);
>>> - if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL,
>>> - cpu_to_node(cpu)))
>>> - return notifier_from_errno(-ENOMEM);
>>> cfd->csd = alloc_percpu(struct call_single_data);
>>> if (!cfd->csd) {
>>> free_cpumask_var(cfd->cpumask);
>>> @@ -64,7 +60,6 @@ hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
>>> case CPU_DEAD:
>>> case CPU_DEAD_FROZEN:
>>> free_cpumask_var(cfd->cpumask);
>>> - free_cpumask_var(cfd->cpumask_ipi);
>>> free_percpu(cfd->csd);
>>> break;
>>> #endif
>>> @@ -255,9 +250,9 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,
>>> csd = &__get_cpu_var(csd_data);
>>>
>>> csd_lock(csd);
>>> -
>>> csd->func = func;
>>> csd->info = info;
>>> +
>>> generic_exec_single(cpu, csd, wait);
>>> } else {
>>> err = -ENXIO; /* CPU not online */
>>> @@ -410,13 +405,6 @@ void smp_call_function_many(const struct cpumask *mask,
>>> if (unlikely(!cpumask_weight(cfd->cpumask)))
>>> return;
>>>
>>> - /*
>>> - * After we put an entry into the list, cfd->cpumask may be cleared
>>> - * again when another CPU sends another IPI for a SMP function call, so
>>> - * cfd->cpumask will be zero.
>>> - */
>>> - cpumask_copy(cfd->cpumask_ipi, cfd->cpumask);
>>> -
>>> for_each_cpu(cpu, cfd->cpumask) {
>>> struct call_single_data *csd = per_cpu_ptr(cfd->csd, cpu);
>>> struct call_single_queue *dst =
>>> @@ -433,7 +421,7 @@ void smp_call_function_many(const struct cpumask *mask,
>>> }
>>>
>>> /* Send a message to all CPUs in the map */
>>> - arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
>>> + arch_send_call_function_ipi_mask(cfd->cpumask);
>>>
>>> if (wait) {
>>> for_each_cpu(cpu, cfd->cpumask) {
>>> --
>>> 1.8.1.2
>> Hi Liu and all
>>
>> Commit 60c323699bb308404dcb60e8808531e02651578a
>> (kernel/smp.c: free related resources when failure occurs in hotplug_cfd())
>> is a fix patch for commit you revert, and it had been merged into mainline.
>>
>> So could you ajust your patch to revert it together? I don't think we need
>> a separate patch to revert 60c323699bb308404dcb60e8808531e02651578a, because
>> your patch haven't be merged.
>>
>> Thanks.
>
> Add Cc:gang.chen@xxxxxxxxxxx
Thank you, and, I should continue trying to familiar with kernel step by
step.
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Chen Gang
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