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Commit 380c4b14 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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tracing/function-graph-tracer: append the tracing_graph_flag 



Impact: Provide a way to pause the function graph tracer

As suggested by Steven Rostedt, the previous patch that prevented from
spinlock function tracing shouldn't use the raw_spinlock to fix it.
It's much better to follow lockdep with normal spinlock, so this patch
adds a new flag for each task to make the function graph tracer able
to be paused. We also can send an ftrace_printk whithout worrying of
the irrelevant traced spinlock during insertion.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8e1b82e0

arch/x86/kernel/ftrace.c

+4 −1
Original line number Diff line number Diff line
@@ -476,7 +476,10 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) 
				&return_to_handler;



	/* Nmi's are currently unsupported */

	if (atomic_read(&in_nmi))

	if (unlikely(atomic_read(&in_nmi)))

		return;



	if (unlikely(atomic_read(&current->tracing_graph_pause)))

		return;



	/*

include/linux/ftrace.h

+13 −0
Original line number Diff line number Diff line
@@ -401,6 +401,16 @@ static inline int task_curr_ret_stack(struct task_struct *t) 
{

	return t->curr_ret_stack;

}



static inline void pause_graph_tracing(void)

{

	atomic_inc(&current->tracing_graph_pause);

}



static inline void unpause_graph_tracing(void)

{

	atomic_dec(&current->tracing_graph_pause);

}

#else



#define __notrace_funcgraph
@@ -412,6 +422,9 @@ static inline int task_curr_ret_stack(struct task_struct *tsk) 
{

	return -1;

}



static inline void pause_graph_tracing(void) { }

static inline void unpause_graph_tracing(void) { }

#endif



#ifdef CONFIG_TRACING

include/linux/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -1379,6 +1379,8 @@ struct task_struct { 
	 * because of depth overrun.

	 */

	atomic_t trace_overrun;

	/* Pause for the tracing */

	atomic_t tracing_graph_pause;

#endif

#ifdef CONFIG_TRACING

	/* state flags for use by tracers */

kernel/trace/ftrace.c

+2 −0
Original line number Diff line number Diff line
@@ -1998,6 +1998,7 @@ static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list) 
			/* Make sure IRQs see the -1 first: */

			barrier();

			t->ret_stack = ret_stack_list[start++];

			atomic_set(&t->tracing_graph_pause, 0);

			atomic_set(&t->trace_overrun, 0);

		}

	} while_each_thread(g, t);
@@ -2077,6 +2078,7 @@ void ftrace_graph_init_task(struct task_struct *t) 
		if (!t->ret_stack)

			return;

		t->curr_ret_stack = -1;

		atomic_set(&t->tracing_graph_pause, 0);

		atomic_set(&t->trace_overrun, 0);

	} else

		t->ret_stack = NULL;

kernel/trace/trace.c

+5 −13
Original line number Diff line number Diff line
@@ -3590,14 +3590,7 @@ static __init int tracer_init_debugfs(void) 


int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)

{

	/*

	 * Raw Spinlock because a normal spinlock would be traced here

	 * and append an irrelevant couple spin_lock_irqsave/

	 * spin_unlock_irqrestore traced by ftrace around this

	 * TRACE_PRINTK trace.

	 */

	static raw_spinlock_t trace_buf_lock =

				(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;

	static DEFINE_SPINLOCK(trace_buf_lock);

	static char trace_buf[TRACE_BUF_SIZE];



	struct ring_buffer_event *event;
@@ -3618,8 +3611,8 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args) 
	if (unlikely(atomic_read(&data->disabled)))

		goto out;



	local_irq_save(flags);

	__raw_spin_lock(&trace_buf_lock);

	pause_graph_tracing();

	spin_lock_irqsave(&trace_buf_lock, irq_flags);

	len = vsnprintf(trace_buf, TRACE_BUF_SIZE, fmt, args);



	len = min(len, TRACE_BUF_SIZE-1);
@@ -3640,9 +3633,8 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args) 
	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);



 out_unlock:

	__raw_spin_unlock(&trace_buf_lock);

	local_irq_restore(flags);



	spin_unlock_irqrestore(&trace_buf_lock, irq_flags);

	unpause_graph_tracing();

 out:

	preempt_enable_notrace();