RE: [tip:x86/urgent] x86/mce: Fix CMCI preemption bugs

[Luck, Tony]

> Hohum, __raw_spin_lock_irqsave does preempt_disable(). And
> machine_check_poll should be running in irq context so why would the
> original issue happen?
>
>> kernel: [    7.341085] BUG: using __this_cpu_write() in preemptible [00000000] code: modprobe/546
>
> Unfortunately, I have only one line in a mail CCed to me.
>
> Color me confused.

Is this just the missing put_cpu() that Chen Gong already sent a patch for?

See attached

-Tony
> --- Begin Message ---
> This bug is introduced by me in commit 27f6c573e0. I forget
> to execute put_cpu_var operation after get_cpu_var. Fix it
> via this_cpu_write instead of get_cpu_var.
>
> v2 -> v1: Separate cleanup from bug fix.
>
> Signed-off-by: Chen, Gong <gong.chen@xxxxxxxxxxxxxxx>
> Suggested-by: H. Peter Anvin <hpa@xxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/mcheck/mce.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index eeee23f..68317c8 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -598,7 +598,6 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
>  {
>         struct mce m;
>         int i;
> -       unsigned long *v;
>
>         this_cpu_inc(mce_poll_count);
>
> @@ -618,8 +617,7 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
>                 if (!(m.status & MCI_STATUS_VAL))
>                         continue;
>
> -               v = &get_cpu_var(mce_polled_error);
> -               set_bit(0, v);
> +               this_cpu_write(mce_polled_error, 1);
>                 /*
>                  * Uncorrected or signalled events are handled by the exception
>                  * handler when it is enabled, so don't process those here.
> --
> 1.9.0
>
>
> --- End Message ---