Patch "x86/tlb/trace: Do not trace on CPU that is offline" has been added to the 3.18-stable tree

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This is a note to let you know that I've just added the patch titled

    x86/tlb/trace: Do not trace on CPU that is offline

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:
     x86-tlb-trace-do-not-trace-on-cpu-that-is-offline.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 6c8465a82a605bc692304bab42703017dcfff013 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Date: Fri, 6 Feb 2015 14:18:19 -0500
Subject: x86/tlb/trace: Do not trace on CPU that is offline

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

commit 6c8465a82a605bc692304bab42703017dcfff013 upstream.

When taking a CPU down for suspend and resume, a tracepoint may be called
when the CPU has been designated offline. As tracepoints require RCU for
protection, they must not be called if the current CPU is offline.

Unfortunately, trace_tlb_flush() is called in this scenario as was noted
by LOCKDEP:

...

 Disabling non-boot CPUs ...
 intel_pstate CPU 1 exiting

 ===============================
 smpboot: CPU 1 didn't die...
 [ INFO: suspicious RCU usage. ]
 3.19.0-rc7-next-20150204.1-iniza-small #1 Not tainted
 -------------------------------
 include/trace/events/tlb.h:35 suspicious rcu_dereference_check() usage!

 other info that might help us debug this:

 RCU used illegally from offline CPU!
 rcu_scheduler_active = 1, debug_locks = 0
 no locks held by swapper/1/0.

 stack backtrace:
 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.19.0-rc7-next-20150204.1-iniza-small #1
 Hardware name: SAMSUNG ELECTRONICS CO., LTD. 530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013
  0000000000000001 ffff88011a44fe18 ffffffff817e370d 0000000000000011
  ffff88011a448290 ffff88011a44fe48 ffffffff810d6847 ffff8800c66b9600
  0000000000000001 ffff88011a44c000 ffffffff81cb3900 ffff88011a44fe78
 Call Trace:
  [<ffffffff817e370d>] dump_stack+0x4c/0x65
  [<ffffffff810d6847>] lockdep_rcu_suspicious+0xe7/0x120
  [<ffffffff810b71a5>] idle_task_exit+0x205/0x2c0
  [<ffffffff81054c4e>] play_dead_common+0xe/0x50
  [<ffffffff81054ca5>] native_play_dead+0x15/0x140
  [<ffffffff8102963f>] arch_cpu_idle_dead+0xf/0x20
  [<ffffffff810cd89e>] cpu_startup_entry+0x37e/0x580
  [<ffffffff81053e20>] start_secondary+0x140/0x150
 intel_pstate CPU 2 exiting

...

By converting the tlb_flush tracepoint to a TRACE_EVENT_CONDITION where the
condition is cpu_online(smp_processor_id()), we can avoid calling RCU protected
code when the CPU is offline.

Link: http://lkml.kernel.org/r/CA+icZUUGiGDoL5NU8RuxKzFjoLjEKRtUWx=JB8B9a0EQv-eGzQ@xxxxxxxxxxxxxx

Fixes: d17d8f9dedb9 "x86/mm: Add tracepoints for TLB flushes"
Reported-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Suggested-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Acked-by: Dave Hansen <dave@xxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

diff --git a/include/trace/events/tlb.h b/include/trace/events/tlb.h
index 13391d288107..0e7635765153 100644
--- a/include/trace/events/tlb.h
+++ b/include/trace/events/tlb.h
@@ -13,11 +13,13 @@
 	{ TLB_LOCAL_SHOOTDOWN,		"local shootdown" },		\
 	{ TLB_LOCAL_MM_SHOOTDOWN,	"local mm shootdown" }
 
-TRACE_EVENT(tlb_flush,
+TRACE_EVENT_CONDITION(tlb_flush,
 
 	TP_PROTO(int reason, unsigned long pages),
 	TP_ARGS(reason, pages),
 
+	TP_CONDITION(cpu_online(smp_processor_id())),
+
 	TP_STRUCT__entry(
 		__field(	  int, reason)
 		__field(unsigned long,  pages)


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
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