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Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

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Pull RCU updates from Paul E. McKenney:

"
 * Update RCU documentation.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/611.

 * Miscellaneous fixes.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/619.

 * Full-system idle detection.  This is for use by Frederic
   Weisbecker's adaptive-ticks mechanism.  Its purpose is
   to allow the timekeeping CPU to shut off its tick when
   all other CPUs are idle.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/648.

 * Improve rcutorture test coverage.  These were posted to LKML at
   https://lkml.org/lkml/2013/8/19/675.
"

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2013-09-03 07:41:11 +02:00
commit 7d992feb76
25 changed files with 1609 additions and 832 deletions
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34
include/linux/ftrace_event.h
View file

@ -359,6 +359,40 @@ do { \
__trace_printk(ip, fmt, ##args); \
} while (0)
/**
* tracepoint_string - register constant persistent string to trace system
* @str - a constant persistent string that will be referenced in tracepoints
*
* If constant strings are being used in tracepoints, it is faster and
* more efficient to just save the pointer to the string and reference
* that with a printf "%s" instead of saving the string in the ring buffer
* and wasting space and time.
*
* The problem with the above approach is that userspace tools that read
* the binary output of the trace buffers do not have access to the string.
* Instead they just show the address of the string which is not very
* useful to users.
*
* With tracepoint_string(), the string will be registered to the tracing
* system and exported to userspace via the debugfs/tracing/printk_formats
* file that maps the string address to the string text. This way userspace
* tools that read the binary buffers have a way to map the pointers to
* the ASCII strings they represent.
*
* The @str used must be a constant string and persistent as it would not
* make sense to show a string that no longer exists. But it is still fine
* to be used with modules, because when modules are unloaded, if they
* had tracepoints, the ring buffers are cleared too. As long as the string
* does not change during the life of the module, it is fine to use
* tracepoint_string() within a module.
*/
#define tracepoint_string(str) \
({ \
static const char *___tp_str __tracepoint_string = str; \
___tp_str; \
})
#define __tracepoint_string __attribute__((section("__tracepoint_str")))
#ifdef CONFIG_PERF_EVENTS
struct perf_event;