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ftrace: selftest protect againt max flip

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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>
This commit is contained in:
Steven Rostedt
2008-05-12 21:20:56 +02:00
committed by Thomas Gleixner
parent d15f57f23e
commit 30afdcb1de
1 changed files with 7 additions and 3 deletions
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10
kernel/trace/trace_selftest.c
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@@ -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) static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
{ {
unsigned long cnt = 0; unsigned long flags, cnt = 0;
int cpu; int cpu, ret = 0;
int 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) { for_each_possible_cpu(cpu) {
if (!head_page(tr->data[cpu])) if (!head_page(tr->data[cpu]))
continue; continue;
@@ -96,6 +98,8 @@ static int trace_test_buffer(struct trace_array *tr, unsigned long *count)
if (ret) if (ret)
break; break;
} }
__raw_spin_unlock(&ftrace_max_lock);
raw_local_irq_restore(flags);
if (count) if (count)
*count = cnt; *count = cnt;