printk: use rcuidle console tracepoint

commit fc98c3c8c9dcafd67adcce69e6ce3191d5306c9c upstream.

Use rcuidle console tracepoint because, apparently, it may be issued
from an idle CPU:

  hw-breakpoint: Failed to enable monitor mode on CPU 0.
  hw-breakpoint: CPU 0 failed to disable vector catch

  ===============================
  [ ERR: suspicious RCU usage.  ]
  4.10.0-rc8-next-20170215+ #119 Not tainted
  -------------------------------
  ./include/trace/events/printk.h:32 suspicious rcu_dereference_check() usage!

  other info that might help us debug this:

  RCU used illegally from idle CPU!
  rcu_scheduler_active = 2, debug_locks = 0
  RCU used illegally from extended quiescent state!
  2 locks held by swapper/0/0:
   #0:  (cpu_pm_notifier_lock){......}, at: [<c0237e2c>] cpu_pm_exit+0x10/0x54
   #1:  (console_lock){+.+.+.}, at: [<c01ab350>] vprintk_emit+0x264/0x474

  stack backtrace:
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.10.0-rc8-next-20170215+ #119
  Hardware name: Generic OMAP4 (Flattened Device Tree)
    console_unlock
    vprintk_emit
    vprintk_default
    printk
    reset_ctrl_regs
    dbg_cpu_pm_notify
    notifier_call_chain
    cpu_pm_exit
    omap_enter_idle_coupled
    cpuidle_enter_state
    cpuidle_enter_state_coupled
    do_idle
    cpu_startup_entry
    start_kernel

This RCU warning, however, is suppressed by lockdep_off() in printk().
lockdep_off() increments the ->lockdep_recursion counter and thus
disables RCU_LOCKDEP_WARN() and debug_lockdep_rcu_enabled(), which want
lockdep to be enabled "current->lockdep_recursion == 0".

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Sergey Senozhatsky <[email protected]>
Reported-by: Tony Lindgren <[email protected]>
Tested-by: Tony Lindgren <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Lindgren <[email protected]>
Cc: Russell King <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Lee Jones <[email protected]>
Change-Id: Ie71569dd763df0acccc224026ddbb66095aac4bf

Author: sergey-senozhatsky

kernel/printk/printk.c

@@ -1412,7 +1412,7 @@ static void call_console_drivers(int level, const char *text, size_t len)
 {
 	struct console *con;
 
-	trace_console(text, len);
+	trace_console_rcuidle(text, len);
 
 	if (level >= console_loglevel && !ignore_loglevel)
 		return;