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Commit 5aa1ba6a authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ftrace: prevent ftrace_special from recursion 



Impact: stop ftrace_special from recursion

The ftrace_special is used to help debug areas of the kernel.
Because of this, if it is put in certain locations, the fact that
it allows recursion can become a problem if the kernel developer
using does not realize that.

This patch changes ftrace_special to not allow recursion into itself
to make it more robust.

It also changes from preempt disable interrupts disable to prevent
any loss of trace entries.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e0cb4ebc

kernel/trace/trace.c

+5 −3
Original line number Diff line number Diff line
@@ -960,6 +960,7 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) 
{

	struct trace_array *tr = &global_trace;

	struct trace_array_cpu *data;

	unsigned long flags;

	int cpu;

	int pc;
@@ -967,14 +968,15 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) 
		return;



	pc = preempt_count();

	preempt_disable_notrace();

	local_irq_save(flags);

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];



	if (likely(!atomic_read(&data->disabled)))

	if (likely(atomic_inc_return(&data->disabled) == 1))

		ftrace_trace_special(tr, data, arg1, arg2, arg3, pc);



	preempt_enable_notrace();

	atomic_dec(&data->disabled);

	local_irq_restore(flags);

}



#ifdef CONFIG_FUNCTION_TRACER