[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>

diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 3e2c05c..04f8c67 100644 (file)
--- 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)