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SubjectRe: [PATCH 5/6] x86, mce: handle "action required" errors
On Mon, Dec 12, 2011 at 01:47:45PM -0800, Tony Luck wrote:
[..]

> - * Called after mce notification in process context. This code
> - * is allowed to sleep. Call the high level VM handler to process
> - * any corrupted pages.
> - * Assume that the work queue code only calls this one at a time
> - * per CPU.
> - * Note we don't disable preemption, so this code might run on the wrong
> - * CPU. In this case the event is picked up by the scheduled work queue.
> - * This is merely a fast path to expedite processing in some common
> - * cases.
> + * Called in process context that interrupted by MCE and marked with
> + * TIF_MCE_NOTFY, just before returning to errorneous userland.
> + * This code is allowed to sleep.
> + * Attempt possible recovery such as calling the high level VM handler to
> + * process any corrupted pages, and kill/signal current process if required.
> */
> void mce_notify_process(void)
> {
> + __u64 paddr = paddr;
> unsigned long pfn;
> - mce_notify_irq();
> - while (mce_ring_get(&pfn))
> - memory_failure(pfn, MCE_VECTOR, 0);
> +
> + if (!mce_find_info(&paddr))
> + mce_panic("Lost address", NULL, NULL);

Wouldn't it be good to return struct mce_info *mi here in addition to
&paddr...

> + pfn = paddr >> PAGE_SHIFT;
> +
> + clear_thread_flag(TIF_MCE_NOTIFY);
> +
> + pr_err("Uncorrected hardware memory error in user-access at %llx",
> + paddr);
> + if (memory_failure(pfn, MCE_VECTOR, MF_ACTION_REQUIRED) < 0) {
> + pr_err("Memory error not recovered");
> + force_sig(SIGBUS, current);
> + } else {
> + pr_err("Memory error recovered");
> + mce_clear_info();

so that you don't need to iterate again over the mce_info array but do:

mce_clear_info(mi);

?

This assumes, of course, that you have only one AR MCE per task, per
return to userspace. I guess this is fine for now.

> + }
> }
>
> static void mce_process_work(struct work_struct *dummy)
> {
> - mce_notify_process();
> + unsigned long pfn;
> +
> + while (mce_ring_get(&pfn))
> + memory_failure(pfn, MCE_VECTOR, 0);
> }
>
> #ifdef CONFIG_X86_MCE_INTEL
> @@ -1232,8 +1246,6 @@ int mce_notify_irq(void)
> /* Not more than two messages every minute */
> static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);
>
> - clear_thread_flag(TIF_MCE_NOTIFY);
> -
> if (test_and_clear_bit(0, &mce_need_notify)) {
> /* wake processes polling /dev/mcelog */
> wake_up_interruptible(&mce_chrdev_wait);
> --
> 1.7.3.1
>

Thanks.

--
Regards/Gruss,
Boris.

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