[S390] ftrace: disable tracing on idle psw

Disable tracing on idle psw. Otherwise it would give us huge
preempt off times for idle. Which is rather pointless.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 3e2c05cb6a8..04f8c67a610 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -136,9 +136,12 @@ static void default_idle(void)
                 return;
         }
         trace_hardirqs_on();
+        /* Don't trace preempt off for idle. */
+        stop_critical_timings();
         /* Wait for external, I/O or machine check interrupt. */
         __load_psw_mask(psw_kernel_bits | PSW_MASK_WAIT |
                         PSW_MASK_IO | PSW_MASK_EXT);
+        start_critical_timings();
 }
 
 void cpu_idle(void)