ftrace: preemptoff selftest not working
authorHeiko Carstens <heiko.carstens@de.ibm.com>
Tue, 18 Nov 2008 17:06:35 +0000 (18:06 +0100)
committerIngo Molnar <mingo@elte.hu>
Tue, 18 Nov 2008 20:54:50 +0000 (21:54 +0100)
commita22506347d038a66506c6f57e9b97104128e280d
tree88a21ea77883d13f92c4eda322b44bbddcd48aee
parent1c80025a49855b12fa09bb6db71820e3367b1369
ftrace: preemptoff selftest not working

Impact: fix preemptoff and preemptirqsoff tracer self-tests

I was wondering why the preemptoff and preemptirqsoff tracer selftests
don't work on s390. After all its just that they get called from
non-preemptible context:

kernel_init() will execute all initcalls, however the first line in
kernel_init() is lock_kernel(), which causes the preempt_count to be
increased. Any later calls to add_preempt_count() (especially those
from the selftests) will therefore not result in a call to
trace_preempt_off() since the check below in add_preempt_count()
will be false:

        if (preempt_count() == val)
                trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));

Hence the trace buffer will be empty.

Fix this by releasing the BKL during the self-tests.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel/trace/trace.c