ftrace: selftest protect againt max flip
There is a slight race condition in the selftest where the max update
of the wakeup and irqs/preemption off tests can be doing a max update as
the buffers are being tested. If this happens the system can crash with
a GPF.
This patch adds the max update spinlock around the checking of the
buffers to prevent such a race.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 83e55a2..395274e 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -82,10 +82,12 @@
*/
static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
{
- unsigned long cnt = 0;
- int cpu;
- int ret = 0;
+ unsigned long flags, cnt = 0;
+ int cpu, ret = 0;
+ /* Don't allow flipping of max traces now */
+ raw_local_irq_save(flags);
+ __raw_spin_lock(&ftrace_max_lock);
for_each_possible_cpu(cpu) {
if (!head_page(tr->data[cpu]))
continue;
@@ -96,6 +98,8 @@
if (ret)
break;
}
+ __raw_spin_unlock(&ftrace_max_lock);
+ raw_local_irq_restore(flags);
if (count)
*count = cnt;