Commit a9f70bd4 authored Feb 17, 2016 by Linus Torvalds

Merge tag 'trace-fixes-v4.5-rc4' of...

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

Pull tracing fixes from Steven Rostedt:
"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)"

* tag 'trace-fixes-v4.5-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Fix freak link error caused by branch tracer
tracepoints: Do not trace when cpu is offline

parents 65c23c65 b33c8ff4

include/linux/compiler.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -144,7 +144,7 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
		*/
		#define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
		#define __trace_if(cond) \
		if (__builtin_constant_p((cond)) ? !!(cond) : \
		if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
		({ \
		int ______r; \
		static struct ftrace_branch_data \

include/linux/tracepoint.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -14,8 +14,10 @@
		* See the file COPYING for more details.
		*/

		#include <linux/smp.h>
		#include <linux/errno.h>
		#include <linux/types.h>
		#include <linux/cpumask.h>
		#include <linux/rcupdate.h>
		#include <linux/tracepoint-defs.h>

		@@ -132,6 +134,9 @@ extern void syscall_unregfunc(void);
		void *it_func; \
		void *__data; \
		\
		if (!cpu_online(raw_smp_processor_id())) \
		return; \
		\
		if (!(cond)) \
		return; \
		prercu; \

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