linux-kernel - Re: [PATCH] x86/oprofile/ppro: Do not use __this

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Date:   Wed, 8 Nov 2017 14:53:57 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Borislav Petkov <bp@...e.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "oprofile-list@...ts.sf.net" <oprofile-list@...ts.sf.net>,
        Robert Richter <rric@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/oprofile/ppro: Do not use __this_cpu* accessors in
 preemptible context

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@...el.com>

Thanks,
Fengguang

>Thx.
>
>---
>From: Borislav Petkov <bp@...e.de>
>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@...el.com>
>Signed-off-by: Borislav Petkov <bp@...e.de>
>Fix-creation-mandated-by: Linus Torvalds <torvalds@...ux-foundation.org>
>Cc: Robert Richter <rric@...nel.org>
>Cc: x86@...nel.org
>---
> 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 Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
>-- 
>