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Commit 3ea2e6d7 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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ftrace: make some tracers reentrant 



Now that the ring buffer is reentrant, some of the ftrace tracers
(sched_swich, debugging traces) can also be reentrant.

Note: Never make the function tracer reentrant, that can cause
  recursion problems all over the kernel. The function tracer
  must disable reentrancy.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bf41a158

kernel/trace/trace.c

+2 −8
Original line number Diff line number Diff line
@@ -839,7 +839,6 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) 
{

	struct trace_array *tr = &global_trace;

	struct trace_array_cpu *data;

	long disabled;

	int cpu;

	int pc;
@@ -850,12 +849,10 @@ ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) 
	preempt_disable_notrace();

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];

	disabled = atomic_inc_return(&data->disabled);



	if (likely(disabled == 1))

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

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



	atomic_dec(&data->disabled);

	preempt_enable_notrace();

}
@@ -2961,7 +2958,6 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
	struct trace_array_cpu *data;

	struct print_entry *entry;

	unsigned long flags, irq_flags;

	long disabled;

	int cpu, len = 0, size, pc;



	if (!tr->ctrl || tracing_disabled)
@@ -2971,9 +2967,8 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
	preempt_disable_notrace();

	cpu = raw_smp_processor_id();

	data = tr->data[cpu];

	disabled = atomic_inc_return(&data->disabled);



	if (unlikely(disabled != 1))

	if (unlikely(atomic_read(&data->disabled)))

		goto out;



	spin_lock_irqsave(&trace_buf_lock, flags);
@@ -2999,7 +2994,6 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
	spin_unlock_irqrestore(&trace_buf_lock, flags);



 out:

	atomic_dec(&data->disabled);

	preempt_enable_notrace();



	return len;

kernel/trace/trace_sched_switch.c

+2 −8
Original line number Diff line number Diff line
@@ -24,7 +24,6 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev, 
{

	struct trace_array_cpu *data;

	unsigned long flags;

	long disabled;

	int cpu;

	int pc;
@@ -41,12 +40,10 @@ probe_sched_switch(struct rq *__rq, struct task_struct *prev, 
	local_irq_save(flags);

	cpu = raw_smp_processor_id();

	data = ctx_trace->data[cpu];

	disabled = atomic_inc_return(&data->disabled);



	if (likely(disabled == 1))

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

		tracing_sched_switch_trace(ctx_trace, data, prev, next, flags, pc);



	atomic_dec(&data->disabled);

	local_irq_restore(flags);

}
@@ -55,7 +52,6 @@ probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee) 
{

	struct trace_array_cpu *data;

	unsigned long flags;

	long disabled;

	int cpu, pc;



	if (!likely(tracer_enabled))
@@ -67,13 +63,11 @@ probe_sched_wakeup(struct rq *__rq, struct task_struct *wakee) 
	local_irq_save(flags);

	cpu = raw_smp_processor_id();

	data = ctx_trace->data[cpu];

	disabled = atomic_inc_return(&data->disabled);



	if (likely(disabled == 1))

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

		tracing_sched_wakeup_trace(ctx_trace, data, wakee, current,

					   flags, pc);



	atomic_dec(&data->disabled);

	local_irq_restore(flags);

}