diff options
| author | Dave Hansen <dave.hansen@linux.intel.com> | 2014-08-07 10:52:04 -0700 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2014-09-10 10:48:46 -0400 |
| commit | 3a630178fd5f30c285fd7016c5340a176b625913 (patch) | |
| tree | 861501d28019011d70cb50abe4c438883bff0795 /include/linux/tracepoint.h | |
| parent | fef5aeeee9e3717e7aea991a7ae9ff6a7a2d4c85 (diff) | |
| download | lwn-3a630178fd5f30c285fd7016c5340a176b625913.tar.gz lwn-3a630178fd5f30c285fd7016c5340a176b625913.zip | |
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.h | 11 |
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)) \ |