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Commit 30afdcb1 authored by Steven Rostedt's avatar Steven Rostedt Committed by Thomas Gleixner
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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: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent d15f57f2

kernel/trace/trace_selftest.c

+7 −3
Original line number Diff line number Diff line
@@ -82,10 +82,12 @@ trace_test_buffer_cpu(struct trace_array *tr, struct trace_array_cpu *data) 
 */

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 @@ static int trace_test_buffer(struct trace_array *tr, unsigned long *count) 
		if (ret)

			break;

	}

	__raw_spin_unlock(&ftrace_max_lock);

	raw_local_irq_restore(flags);



	if (count)

		*count = cnt;