diff options
| author | Steven Rostedt <rostedt@goodmis.org> | 2013-05-28 22:38:42 +0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2013-05-29 06:47:13 +0400 |
| commit | 12bcbe66d7b3cc9f9f86cd02f925666eaa3c2107 (patch) | |
| tree | 54e70e0f7450aedfee1418742758dc538d9649e5 /include/linux/rcupdate.h | |
| parent | 6721cb60022629ae76365551f05d9658b8d14c55 (diff) | |
| download | linux-12bcbe66d7b3cc9f9f86cd02f925666eaa3c2107.tar.xz | |
rcu: Add _notrace variation of rcu_dereference_raw() and hlist_for_each_entry_rcu()
As rcu_dereference_raw() under RCU debug config options can add quite a
bit of checks, and that tracing uses rcu_dereference_raw(), these checks
happen with the function tracer. The function tracer also happens to trace
these debug checks too. This added overhead can livelock the system.
Add a new interface to RCU for both rcu_dereference_raw_notrace() as well
as hlist_for_each_entry_rcu_notrace() as the hlist iterator uses the
rcu_dereference_raw() as well, and is used a bit with the function tracer.
Link: http://lkml.kernel.org/r/20130528184209.304356745@goodmis.org
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4ccd68e49b00..ddcc7826d907 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -640,6 +640,15 @@ static inline void rcu_preempt_sleep_check(void) #define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/ +/* + * The tracing infrastructure traces RCU (we want that), but unfortunately + * some of the RCU checks causes tracing to lock up the system. + * + * The tracing version of rcu_dereference_raw() must not call + * rcu_read_lock_held(). + */ +#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu) + /** * rcu_access_index() - fetch RCU index with no dereferencing * @p: The index to read |