On Thu, May 22, 2014 at 08:32:20AM +0800, Chen Yucong wrote:
> mces_seen is a Per-CPU variable which should only be accessed by Per-CPU as possible. So the
> clear operation of mces_seen should also be local to Per-CPU rather than monarch CPU.
>
> Meanwhile, there is also a potential risk that mces_seen will not be be cleared if a timeout
> occurs in mce_end for monarch CPU. As a result, the stale value of mces_seen will reappear
> on the next mce.
>
> Based on the above reasons, this patch distribute the clear operation of mces_seen to Per-CPU
> rather than only monarch CPU.
>
> * From v1
> * Add Reviewed-by: Andi Kleen
> * Put the clear operation of mces_seen before the MCG_STATUS write.
>
> * From v2
> * Fix some misspelling in the patch message.
>
> Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Signed-off-by: Chen Yucong <slaoub@xxxxxxxxx>
This patch is purely x86_64 MCE related matter, so you need add proper
recipients to be properly reviewed.
Personally I'm OK for this code change (it reduces the processing time of
monarch CPU somewhat, I think it's a small benefit), but you got complainments
in ver.2, so please make some consensus.
And please fix misspelling in subject s/Distirbute/Distribute/.
Thanks,
Naoya Horiguchi
> ---
> arch/x86/kernel/cpu/mcheck/mce.c | 18 +++++++-----------
> 1 file changed, 7 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 68317c8..966a5f5 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -785,13 +785,6 @@ static void mce_reign(void)
> */
> if (global_worst <= MCE_KEEP_SEVERITY && mca_cfg.tolerant < 3)
> mce_panic("Machine check from unknown source", NULL, NULL);
> -
> - /*
> - * Now clear all the mces_seen so that they don't reappear on
> - * the next mce.
> - */
> - for_each_possible_cpu(cpu)
> - memset(&per_cpu(mces_seen, cpu), 0, sizeof(struct mce));
> }
>
> static atomic_t global_nwo;
> @@ -1137,9 +1130,6 @@ void do_machine_check(struct pt_regs *regs, long error_code)
> }
> }
>
> - /* mce_clear_state will clear *final, save locally for use later */
> - m = *final;
> -
> if (!no_way_out)
> mce_clear_state(toclear);
>
> @@ -1161,7 +1151,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
> mce_panic("Fatal machine check on current CPU", &m, msg);
> if (worst == MCE_AR_SEVERITY) {
> /* schedule action before return to userland */
> - mce_save_info(m.addr, m.mcgstatus & MCG_STATUS_RIPV);
> + mce_save_info(final->addr, final->mcgstatus & MCG_STATUS_RIPV);
> set_thread_flag(TIF_MCE_NOTIFY);
> } else if (kill_it) {
> force_sig(SIGBUS, current);
> @@ -1170,6 +1160,12 @@ void do_machine_check(struct pt_regs *regs, long error_code)
>
> if (worst > 0)
> mce_report_event(regs);
> +
> + /*
> + * Now clear the mces_seen of current CPU -*final - so that it does not
> + * reappear on the next mce.
> + */
> + memset(final, 0, sizeof(struct mce));
> mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
> out:
> atomic_dec(&mce_entry);
> --
> 1.7.10.4
>
>
>
>
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