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authorDave Hansen <dave.hansen@linux.intel.com>2014-08-07 10:52:04 -0700
committerSteven Rostedt <rostedt@goodmis.org>2014-09-10 10:48:46 -0400
commit3a630178fd5f30c285fd7016c5340a176b625913 (patch)
tree861501d28019011d70cb50abe4c438883bff0795 /include/linux/tracepoint.h
parentfef5aeeee9e3717e7aea991a7ae9ff6a7a2d4c85 (diff)
tracing: generate RCU warnings even when tracepoints are disabled
Dave Jones reported seeing a bug from one of my TLB tracepoints: http://lkml.kernel.org/r/20140806181801.GA4605@redhat.com I've been running these patches for months and never saw this. But, a big chunk of my testing, especially with all the debugging enabled, was in a vm where intel_idle doesn't work. On the systems where I was using intel_idle, I never had lockdep enabled and this tracepoint on at the same time. This patch ensures that whenever we have lockdep available, we do _some_ RCU activity at the site of the tracepoint, despite whether the tracepoint's condition matches or even if the tracepoint itself is completely disabled. This is a bit of a hack, but it is pretty self-contained. I confirmed that with this patch plus lockdep I get the same splat as Dave Jones did, but without enabling the tracepoint explicitly. Link: http://lkml.kernel.org/p/20140807175204.C257CAC5@viggo.jf.intel.com Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dave Hansen <dave@sr71.net> Cc: Dave Jones <davej@redhat.com>, Cc: paulmck@linux.vnet.ibm.com Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/tracepoint.h')
-rw-r--r--include/linux/tracepoint.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index b1293f15f592..e08e21e5f601 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -157,6 +157,12 @@ extern void syscall_unregfunc(void);
* Make sure the alignment of the structure in the __tracepoints section will
* not add unwanted padding between the beginning of the section and the
* structure. Force alignment to the same alignment as the section start.
+ *
+ * When lockdep is enabled, we make sure to always do the RCU portions of
+ * the tracepoint code, regardless of whether tracing is on or we match the
+ * condition. This lets us find RCU issues triggered with tracepoints even
+ * when this tracepoint is off. This code has no purpose other than poking
+ * RCU a bit.
*/
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
extern struct tracepoint __tracepoint_##name; \
@@ -167,6 +173,11 @@ extern void syscall_unregfunc(void);
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond),,); \
+ if (IS_ENABLED(CONFIG_LOCKDEP)) { \
+ rcu_read_lock_sched_notrace(); \
+ rcu_dereference_sched(__tracepoint_##name.funcs);\
+ rcu_read_unlock_sched_notrace(); \
+ } \
} \
__DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args), \
PARAMS(cond), PARAMS(data_proto), PARAMS(data_args)) \