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author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-06-08 01:46:51 (GMT) |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-06-08 01:46:51 (GMT) |
commit | 14d0ee051753f30e23033bdb153110f00b03c8ce (patch) | |
tree | 88a19ee630628e8904b96b586521d3f3755c14b8 /include | |
parent | ea7f665612fcc73da6b7698f468cd5fc03a30d47 (diff) | |
parent | f17a5194859a82afe4164e938b92035b86c55794 (diff) | |
download | linux-14d0ee051753f30e23033bdb153110f00b03c8ce.tar.xz |
Merge tag 'trace-fixes-v3.10-rc3-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt:
"This contains 4 fixes.
The first two fix the case where full RCU debugging is enabled,
enabling function tracing causes a live lock of the system. This is
due to the added debug checks in rcu_dereference_raw() that is used by
the function tracer. These checks are also traced by the function
tracer as well as cause enough overhead to the function tracer to slow
down the system enough that the time to finish an interrupt can take
longer than when the next interrupt is triggered, causing a live lock
from the timer interrupt.
Talking this over with Paul McKenney, we came up with a fix that adds
a new rcu_dereference_raw_notrace() that does not perform these added
checks, and let the function tracer use that.
The third commit fixes a failed compile when branch tracing is
enabled, due to the conversion of the trace_test_buffer() selftest
that the branch trace wasn't converted for.
The forth patch fixes a bug caught by the RCU lockdep code where a
rcu_read_lock() is performed when rcu is disabled (either going to or
from idle, or user space). This happened on the irqsoff tracer as it
calls task_uid(). The fix here was to use current_uid() when possible
that doesn't use rcu locking. Which luckily, is always used when
irqsoff calls this code."
* tag 'trace-fixes-v3.10-rc3-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Use current_uid() for critical time tracing
tracing: Fix bad parameter passed in branch selftest
ftrace: Use the rcu _notrace variants for rcu_dereference_raw() and friends
rcu: Add _notrace variation of rcu_dereference_raw() and hlist_for_each_entry_rcu()
Diffstat (limited to 'include')
-rw-r--r-- | include/linux/rculist.h | 20 | ||||
-rw-r--r-- | include/linux/rcupdate.h | 9 |
2 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 8089e35..f4b1001 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -461,6 +461,26 @@ static inline void hlist_add_after_rcu(struct hlist_node *prev, &(pos)->member)), typeof(*(pos)), member)) /** + * hlist_for_each_entry_rcu_notrace - iterate over rcu list of given type (for tracing) + * @pos: the type * to use as a loop cursor. + * @head: the head for your list. + * @member: the name of the hlist_node within the struct. + * + * This list-traversal primitive may safely run concurrently with + * the _rcu list-mutation primitives such as hlist_add_head_rcu() + * as long as the traversal is guarded by rcu_read_lock(). + * + * This is the same as hlist_for_each_entry_rcu() except that it does + * not do any RCU debugging or tracing. + */ +#define hlist_for_each_entry_rcu_notrace(pos, head, member) \ + for (pos = hlist_entry_safe (rcu_dereference_raw_notrace(hlist_first_rcu(head)),\ + typeof(*(pos)), member); \ + pos; \ + pos = hlist_entry_safe(rcu_dereference_raw_notrace(hlist_next_rcu(\ + &(pos)->member)), typeof(*(pos)), member)) + +/** * hlist_for_each_entry_rcu_bh - iterate over rcu list of given type * @pos: the type * to use as a loop cursor. * @head: the head for your list. diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4ccd68e..ddcc782 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 |