linux-kernel - Re: [PATCH v2] x86,mm: print likely CPU at segfault time

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Date:   Fri, 5 Aug 2022 09:59:29 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Rik van Riel <riel@...riel.com>
Cc:     Dave Hansen <dave.hansen@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        Thomas Gleixner <tglx@...utronix.de>, Dave Jones <dsj@...com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH v2]  x86,mm: print likely CPU at segfault time


* Rik van Riel <riel@...riel.com> wrote:

> The show_unhandled_signals variable seems to be controlled through 
> /proc/sys/debug/exception-trace, and be on by default.

Indeed ... then this too should be pointed out in the changelog.

Plus the patch doesn't build on top of the latest upstream kernel, 
x86-defconfig:

  CC      arch/x86/mm/fault.o
  In file included from ./arch/x86/include/generated/asm/rwonce.h:1,
                  from ./include/linux/compiler.h:248,
                  from ./arch/x86/include/asm/current.h:5,
                  from ./include/linux/sched.h:12,
                  from arch/x86/mm/fault.c:7:
  arch/x86/mm/fault.c: In function ‘show_signal_msg’:
  ./include/asm-generic/rwonce.h:44:71: error: lvalue required as unary ‘&’ operand
     44 | #define __READ_ONCE(x)  (*(const volatile __unqual_scalar_typeof(x) *)&(x))
        |                                                                       ^
  ./include/asm-generic/rwonce.h:50:9: note: in expansion of macro ‘__READ_ONCE’
     50 |         __READ_ONCE(x);                                                 \
        |         ^~~~~~~~~~~
  arch/x86/mm/fault.c:773:19: note: in expansion of macro ‘READ_ONCE’
    773 |         int cpu = READ_ONCE(raw_smp_processor_id());
        |                   ^~~~~~~~~
  make[2]: *** [scripts/Makefile.build:249: arch/x86/mm/fault.o] Error 1

Thanks,

	Ingo