linux-kernel - [PATCH 0/2] [GIT PULL] tracing: A couple of fixes

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Date:	Tue, 16 Feb 2016 14:49:08 -0500
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>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [PATCH 0/2] [GIT PULL] tracing: A couple of fixes

Linus,

This includes two fixes.

The first is something that has come up a few times and has been
worked out individually, but it's come up now enough that the problem
should be generic. Tracepoints are protected by RCU sched. There are
several tracepoints within core infrastructure like kfree().
If a tracepoint is called when the CPU is going down, or when it's
coming up but has yet to be recognized by RCU, a RCU warning is
triggered. This is a true bug as that tracepoint is not protected by
RCU. Usually, this is taken care of by testing for cpu online as
a tracepoint condition. But as this is happening more often, moving
it from a individual tracepoint to a check in the tracepoint infrastructure
is more robust.

Note, there is now a duplicate of a cpu online test, because this update
does not remove the individual checks. But the overhead is small enough
that the removal can be done in another release.

The second change is strange linker breakage due to the branch tracer's
builtin_constant_p() check failing, and treating the condition as a
variable instead of a constant. Arnd Bergmann found that this can be
fixed by testing !!(cond) instead of just (cond).

Please pull the latest trace-fixes-v4.5-rc4 tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
trace-fixes-v4.5-rc4

Tag SHA1: abfeb62bfa1a219b42a0e984db59f6535a741b17
Head SHA1: b33c8ff4431a343561e2319f17c14286f2aa52e2

Arnd Bergmann (1):
      tracing: Fix freak link error caused by branch tracer

Steven Rostedt (Red Hat) (1):
      tracepoints: Do not trace when cpu is offline

----
 include/linux/compiler.h   | 2 +-
 include/linux/tracepoint.h | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)