This is a note to let you know that I've just added the patch titled
tracing: Add condition check to RCU lockdep checks
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-add-condition-check-to-rcu-lockdep-checks.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From a05d59a5673339ef6936d6940cdf68172ce75b9f Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Fri, 6 Feb 2015 14:30:50 -0500
Subject: tracing: Add condition check to RCU lockdep checks
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
commit a05d59a5673339ef6936d6940cdf68172ce75b9f upstream.
The trace_tlb_flush() tracepoint can be called when a CPU is going offline.
When a CPU is offline, RCU is no longer watching that CPU and since the
tracepoint is protected by RCU, it must not be called. To prevent the
tlb_flush tracepoint from being called when the CPU is offline, it was
converted to a TRACE_EVENT_CONDITION where the condition checks if the
CPU is online before calling the tracepoint.
Unfortunately, this was not enough to stop lockdep from complaining about
it. Even though the RCU protected code of the tracepoint will never be
called, the condition is hidden within the tracepoint, and even though the
condition prevents RCU code from being called, the lockdep checks are
outside the tracepoint (this is to test tracepoints even when they are not
enabled).
Even though tracepoints should be checked to be RCU safe when they are not
enabled, the condition should still be considered when checking RCU.
Link: http://lkml.kernel.org/r/CA+icZUUGiGDoL5NU8RuxKzFjoLjEKRtUWx=JB8B9a0EQv-eGzQ@xxxxxxxxxxxxxx
Fixes: 3a630178fd5f "tracing: generate RCU warnings even when tracepoints are disabled"
Acked-by: Dave Hansen <dave@xxxxxxxx>
Reported-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index e08e21e5f601..c72851328ca9 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -173,7 +173,7 @@ extern void syscall_unregfunc(void);
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond),,); \
- if (IS_ENABLED(CONFIG_LOCKDEP)) { \
+ if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
rcu_read_lock_sched_notrace(); \
rcu_dereference_sched(__tracepoint_##name.funcs);\
rcu_read_unlock_sched_notrace(); \
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-3.18/tracing-add-condition-check-to-rcu-lockdep-checks.patch
queue-3.18/x86-tlb-trace-do-not-trace-on-cpu-that-is-offline.patch
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html