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authorHeiko Carstens <heiko.carstens@de.ibm.com>2008-11-18 18:06:35 +0100
committerIngo Molnar <mingo@elte.hu>2008-11-18 21:54:50 +0100
commita22506347d038a66506c6f57e9b97104128e280d (patch)
tree88a21ea77883d13f92c4eda322b44bbddcd48aee /kernel/trace
parent1c80025a49855b12fa09bb6db71820e3367b1369 (diff)
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>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/trace.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 396fda034e3..16892121cb7 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -532,6 +532,13 @@ int register_tracer(struct tracer *type)
}
#ifdef CONFIG_FTRACE_STARTUP_TEST
+ /*
+ * When this gets called we hold the BKL which means that preemption
+ * is disabled. Various trace selftests however need to disable
+ * and enable preemption for successful tests. So we drop the BKL here
+ * and grab it after the tests again.
+ */
+ unlock_kernel();
if (type->selftest) {
struct tracer *saved_tracer = current_trace;
struct trace_array *tr = &global_trace;
@@ -562,6 +569,7 @@ int register_tracer(struct tracer *type)
}
printk(KERN_CONT "PASSED\n");
}
+ lock_kernel();
#endif
type->next = trace_types;