Re: [PATCH] x86/oprofile/ppro: Do not use __this_cpu* accessors in preemptible context

[Fengguang Wu]

On Tue, Nov 07, 2017 at 06:53:07PM +0100, Borislav Petkov wrote:
> On Tue, Nov 07, 2017 at 08:43:40AM -0800, Linus Torvalds wrote:
> > So I'm adding Borislav to the cc just to maybe annoy him into sending
> > in a patch for this thing too..
>
> /me runs away like the wind!
>
> > This is the famous "you touched it last, tag you're it" model of
> > kernel maintainership.
>
> Oh great, like I don't have enough crappy code to maintain already.
>
> And besides, I'm sure Robert would've addressed it eventually, once he
> moves his head up from Cavium-land. Oh well, it is simple enough, lemme
> take care of it. :-)
>
> Fengguang, please run it to confirm.

Yes it fixed the problem!

Tested-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>

Thanks,
Fengguang

> Thx.
>
> ---
> From: Borislav Petkov <bp@xxxxxxx>
> Subject: [PATCH] x86/oprofile/ppro: Do not use __this_cpu* accessors in preemptible context
>
> The warning below says it all. And we should not have used those
> accessors in the first place: it is PPro so no mixed silicon revisions
> and thus can simply use boot_cpu_data.
>
>  BUG: using __this_cpu_read() in preemptible [00000000] code: swapper/0/1
>  caller is __this_cpu_preempt_check
>  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.0-rc8 #4
>  Call Trace:
>   dump_stack
>   check_preemption_disabled
>   ? do_early_param
>   __this_cpu_preempt_check
>   arch_perfmon_init
>   op_nmi_init
>   ? alloc_pci_root_info
>   oprofile_arch_init
>   oprofile_init
>   do_one_initcall
>   ...
>
> Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Fix-creation-mandated-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Robert Richter <rric@xxxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> ---
> arch/x86/oprofile/op_model_ppro.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
> index 350f7096baac..1c3b400b05ce 100644
> --- a/arch/x86/oprofile/op_model_ppro.c
> +++ b/arch/x86/oprofile/op_model_ppro.c
> @@ -212,8 +212,9 @@ static void arch_perfmon_setup_counters(void)
> 	eax.full = cpuid_eax(0xa);
>
> 	/* Workaround for BIOS bugs in 6/15. Taken from perfmon2 */
> -	if (eax.split.version_id == 0 && __this_cpu_read(cpu_info.x86) == 6 &&
> -		__this_cpu_read(cpu_info.x86_model) == 15) {
> +	if (eax.split.version_id == 0 &&
> +	    boot_cpu_data.x86 == 6 &&
> +	    boot_cpu_data.x86_model == 15) {
> 		eax.split.version_id = 2;
> 		eax.split.num_counters = 2;
> 		eax.split.bit_width = 40;
> --
> 2.13.0
>
> SUSE Linux GmbH, GF: Felix ImendÃrffer, Jane Smithard, Graham Norton, HRB 21284 (AG NÃrnberg)
> --