linux-kernel - [PATCH 0/3] Kill off show_stack() NULL-implies-current idiom

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Message-Id: <1474902979-18436-1-git-send-email-mark.rutland@arm.com>
Date:   Mon, 26 Sep 2016 16:16:16 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 0/3] Kill off show_stack() NULL-implies-current idiom

Today, show_stack() accepts a NULL task parameter, which it takes to mean the
current task. However, as noted in tip/x86/asm commit:

  81539169f283329f ("x86/dumpstack: Remove NULL task pointer convention")

... having a NULL task parameter imply current leads to subtle bugs in stack
walking code (so far seen on both 86 and arm64), makes callsites harder to
read, and is unnecessary as all callers have access to current.

As a step towards removing the problematic NULL-implies-current idiom entirely,
these patches ensure that generic code explictly passes current to
show_stack(), rather than relying on arch code to handle NULL.

Thanks,
Mark.

Mark Rutland (3):
  sched: document that show_stack() should not be passed a NULL task
  drivers/tty: Explicitly pass current to show_stack
  lib: dump_stack: explicitly pass current to show_stack

 drivers/tty/sysrq.c   | 2 +-
 include/linux/sched.h | 3 +++
 lib/dump_stack.c      | 2 +-
 3 files changed, 5 insertions(+), 2 deletions(-)

-- 
2.7.4