[PATCH] printk: Do not disable preemption when calling consoles in RT

[Steven Rostedt (VMware)]

console_unlock() may call consoles that call spin_lock(), where spin_lock is
a mutex in PREEMPT_RT. Although mainline may be worried about preempted
holders of the console lock from preventing printk() output, the RT kernel
does not.

Use migrate_disable() to disable preemption when !RT, but we really don't
care if the task stays on the CPU or not for RT. It just has to be able to
schedule.

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 kernel/printk/printk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 8a7c4f79fca0..029ae3caa80e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1811,7 +1811,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		 * console_sem which would prevent anyone from printing to
 		 * console
 		 */
-		preempt_disable();
+		migrate_disable();
 		/*
 		 * Try to acquire and then immediately release the console
 		 * semaphore.  The release will print out buffers and wake up
@@ -1819,7 +1819,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		 */
 		if (may_trylock && console_trylock())
 			console_unlock();
-		preempt_enable();
+		migrate_enable();
 	}
 
 	return printed_len;
-- 
2.19.2