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

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=[e-mail]

Cc: [e-mail] # 3.17+
Fixes: d17d8f9dedb9 "x86/mm: Add tracepoints for TLB flushes"
Reported-by: Sedat Dilek <[e-mail]>
Tested-by: Sedat Dilek <[e-mail]>
Suggested-by: Paul E. McKenney <[e-mail]>
Acked-by: Paul E. McKenney <[e-mail]>
Acked-by: Dave Hansen <[e-mail]>
Signed-off-by: Steven Rostedt <[e-mail]>

include/trace/events/tlb.h

···
 	{ 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)