linux-kernel - [PATCH 0/2] [GIT PULL] tracing: Fix RCU warnings in stack tracer

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Date:	Thu, 22 Oct 2015 09:20:44 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 0/2] [GIT PULL] tracing: Fix RCU warnings in stack tracer

Linus,

Running tests on other changes, the system locked up due to lots
of warnings. It was caused by the stack tracer triggering a warning
about using rcu_dereference() when RCU was not watching. This can happen
due to the fact that the stack tracer uses the function tracer to check
each function, and there's functions that may be called and traced
when RCU stopped watching. Namely when a function is called just before
going idle or to userspace and after RCU stopped watching that current
CPU.

The first patch makes sure that RCU is watching when the stack tracer
uses RCU. The second patch is to make sure that the stack tracer does
not get called by functions in NMI, as it's not NMI safe.

Please pull the latest trace-fixes-v4.3-rc6 tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-fixes-v4.3-rc6

Tag SHA1: 520ef22047724f1fae143e504b4da9737e50d32c
Head SHA1: 1904be1b6bb92058c8e00063dd59df2df294e258

Steven Rostedt (Red Hat) (2):
      tracing: Have stack tracer force RCU to be watching
      tracing: Do not allow stack_tracer to record stack in NMI

----
 kernel/trace/trace_stack.c | 11 +++++++++++
 1 file changed, 11 insertions(+)
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