linux-kernel - [PATCH 3.16 175/204] x86/oprofile/ppro: Do not use __this

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Message-ID: <lsq.1514480744.969353441@decadent.org.uk>
Date:   Thu, 28 Dec 2017 17:05:44 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Fengguang Wu" <fengguang.wu@...el.com>,
        "Borislav Petkov" <bp@...e.de>, "Robert Richter" <rric@...nel.org>,
        x86@...nel.org, "Thomas Gleixner" <tglx@...utronix.de>
Subject: [PATCH 3.16 175/204] x86/oprofile/ppro: Do not use __this_cpu*()
 in preemptible context

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Borislav Petkov <bp@...e.de>

commit a743bbeef27b9176987ec0cb7f906ab0ab52d1da upstream.

The warning below says it all:

  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
   ...

These accessors should not have been used in the first place: it is PPro so
no mixed silicon revisions and thus it can simply use boot_cpu_data.

Reported-by: Fengguang Wu <fengguang.wu@...el.com>
Tested-by: Fengguang Wu <fengguang.wu@...el.com>
Fix-creation-mandated-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Robert Richter <rric@...nel.org>
Cc: x86@...nel.org
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/oprofile/op_model_ppro.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -212,8 +212,8 @@ static void arch_perfmon_setup_counters(
 	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;