From: Steven Rostedt Date: Mon, 12 May 2008 19:20:56 +0000 (+0200) Subject: ftrace: selftest protect againt max flip X-Git-Tag: v2.6.27-rc1~1102^2^2~1^2~63 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=30afdcb1de0a37a2086145a82ca3febebe47d019;p=linux-2.6 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 Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index 83e55a2000..395274e783 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -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;