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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: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-11-10 23:07:30 -05:00 committed by Ingo Molnar
parent e0cb4ebcd9
commit 5aa1ba6a6c
1 changed files with 5 additions and 3 deletions
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8
kernel/trace/trace.c
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@ -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