Hello,
Sorry about the delay. Was traveling.
On Thu, Sep 27, 2012 at 05:19:46PM +0800, Tang Chen wrote:
> 1. cmci_rediscover() is only called by the CPU_POST_DEAD event handler, which
> means the corresponding cpu has already dead. As a result, it won't be
> accessed
> in the for_each_online_cpu loop.
> So, we could change the if(cpu == dying) statement into a BUG_ON().
Let's please move this to a separate patch and use WARN_ON_ONCE()
instead.
> 2. cmci_rediscover() used set_cpus_allowed_ptr() to change the current
> process's
> running cpu, and migrate itself to the dest cpu. But worker processes are not
> allowed to be migrated. If current is a worker, the worker will be migrated to
> another cpu, but the corresponding worker_pool is still on the original cpu.
>
> In this case, the following BUG_ON in try_to_wake_up_local() will be
> triggered:
> BUG_ON(rq != this_rq());
>
> This will cause the kernel panic.
>
> This patch removes the set_cpus_allowed_ptr() call, and put the cmci
> rediscover
> jobs onto all the other cpus using system_wq. This could bring some delay for
> the jobs.
...
> Signed-off-by: Tang Chen <tangc...@cn.fujitsu.com>
> Signed-off-by: Miao Xie <mi...@cn.fujitsu.com>
After separating out the fix part into a separate patch, please add
Cc: sta...@vger.kernel.org.
> void cmci_rediscover(int dying)
> {
> - int banks;
> - int cpu;
> - cpumask_var_t old;
> + int cpu, banks;
>
> if (!cmci_supported(&banks))
> return;
> - if (!alloc_cpumask_var(&old, GFP_KERNEL))
> - return;
> - cpumask_copy(old, ¤t->cpus_allowed);
>
> for_each_online_cpu(cpu) {
> - if (cpu == dying)
> - continue;
> - if (set_cpus_allowed_ptr(current, cpumask_of(cpu)))
> + BUG_ON(cpu == dying);
> +
> + if (cpu == smp_processor_id()) {
> + cmci_rediscover_work_func(NULL);
> continue;
> - /* Recheck banks in case CPUs don't all have the same */
> - if (cmci_supported(&banks))
> - cmci_discover(banks, 0);
> - }
> + }
>
> - set_cpus_allowed_ptr(current, old);
> - free_cpumask_var(old);
> + work_on_cpu(cpu, cmci_rediscover_work_func, NULL);
> + }
The change looks correct to me but fails to apply to the current
mainline.
Thanks!
--
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
