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

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Date:   Tue, 7 Nov 2017 18:53:07 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Fengguang Wu <fengguang.wu@...el.com>
Cc:     "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: [PATCH] x86/oprofile/ppro: Do not use __this_cpu* accessors in
 preemptible context

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.

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)
--