Messages in this thread Patch in this message | | | Date | Mon, 10 Nov 2008 23:11:15 -0500 | From | Steven Rostedt <> | Subject | [PATCH 1/2] ftrace: prevent ftrace_special from recursion |
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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> --- kernel/trace/trace.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5d3dd8a..50f3237 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -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 -- 1.5.6.5 --
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