Commit b1169cc6 authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
Browse files

tracing: Remove mock up poll wait function 



Now that the ring buffer has a built in way to wake up readers
when there's data, using irq_work such that it is safe to do it
in any context. But it was still using the old "poor man's"
wait polling that checks every 1/10 of a second to see if it
should wake up a waiter. This makes the latency for a wake up
excruciatingly long. No need to do that anymore.

Completely remove the different wait_poll types from the tracers
and have them all use the default one now.

Reported-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f4874261

kernel/trace/trace.c

+4 −25
Original line number Diff line number Diff line
@@ -1085,7 +1085,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu) 
}

#endif /* CONFIG_TRACER_MAX_TRACE */



static void default_wait_pipe(struct trace_iterator *iter)

static void wait_on_pipe(struct trace_iterator *iter)

{

	/* Iterators are static, they should be filled or empty */

	if (trace_buffer_iter(iter, iter->cpu_file))
@@ -1202,8 +1202,6 @@ int register_tracer(struct tracer *type) 
	else

		if (!type->flags->opts)

			type->flags->opts = dummy_tracer_opt;

	if (!type->wait_pipe)

		type->wait_pipe = default_wait_pipe;



	ret = run_tracer_selftest(type);

	if (ret < 0)
@@ -4207,25 +4205,6 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table) 
	return trace_poll(iter, filp, poll_table);

}



/*

 * This is a make-shift waitqueue.

 * A tracer might use this callback on some rare cases:

 *

 *  1) the current tracer might hold the runqueue lock when it wakes up

 *     a reader, hence a deadlock (sched, function, and function graph tracers)

 *  2) the function tracers, trace all functions, we don't want

 *     the overhead of calling wake_up and friends

 *     (and tracing them too)

 *

 *     Anyway, this is really very primitive wakeup.

 */

void poll_wait_pipe(struct trace_iterator *iter)

{

	set_current_state(TASK_INTERRUPTIBLE);

	/* sleep for 100 msecs, and try again. */

	schedule_timeout(HZ / 10);

}



/* Must be called with trace_types_lock mutex held. */

static int tracing_wait_pipe(struct file *filp)

{
@@ -4251,7 +4230,7 @@ static int tracing_wait_pipe(struct file *filp) 


		mutex_unlock(&iter->mutex);



		iter->trace->wait_pipe(iter);

		wait_on_pipe(iter);



		mutex_lock(&iter->mutex);
@@ -5179,7 +5158,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, 
				goto out_unlock;

			}

			mutex_unlock(&trace_types_lock);

			iter->trace->wait_pipe(iter);

			wait_on_pipe(iter);

			mutex_lock(&trace_types_lock);

			if (signal_pending(current)) {

				size = -EINTR;
@@ -5390,7 +5369,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, 
			goto out;

		}

		mutex_unlock(&trace_types_lock);

		iter->trace->wait_pipe(iter);

		wait_on_pipe(iter);

		mutex_lock(&trace_types_lock);

		if (signal_pending(current)) {

			ret = -EINTR;

kernel/trace/trace.h

+0 −4
Original line number Diff line number Diff line
@@ -338,7 +338,6 @@ struct tracer_flags { 
 * @stop: called when tracing is paused (echo 0 > tracing_enabled)

 * @open: called when the trace file is opened

 * @pipe_open: called when the trace_pipe file is opened

 * @wait_pipe: override how the user waits for traces on trace_pipe

 * @close: called when the trace file is released

 * @pipe_close: called when the trace_pipe file is released

 * @read: override the default read callback on trace_pipe
@@ -357,7 +356,6 @@ struct tracer { 
	void			(*stop)(struct trace_array *tr);

	void			(*open)(struct trace_iterator *iter);

	void			(*pipe_open)(struct trace_iterator *iter);

	void			(*wait_pipe)(struct trace_iterator *iter);

	void			(*close)(struct trace_iterator *iter);

	void			(*pipe_close)(struct trace_iterator *iter);

	ssize_t			(*read)(struct trace_iterator *iter,
@@ -566,8 +564,6 @@ void trace_init_global_iter(struct trace_iterator *iter); 


void tracing_iter_reset(struct trace_iterator *iter, int cpu);



void poll_wait_pipe(struct trace_iterator *iter);



void tracing_sched_switch_trace(struct trace_array *tr,

				struct task_struct *prev,

				struct task_struct *next,

kernel/trace/trace_functions.c

+0 −1
Original line number Diff line number Diff line
@@ -252,7 +252,6 @@ static struct tracer function_trace __tracer_data = 
	.init		= function_trace_init,

	.reset		= function_trace_reset,

	.start		= function_trace_start,

	.wait_pipe	= poll_wait_pipe,

	.flags		= &func_flags,

	.set_flag	= func_set_flag,

	.allow_instances = true,

kernel/trace/trace_functions_graph.c

+0 −1
Original line number Diff line number Diff line
@@ -1505,7 +1505,6 @@ static struct tracer graph_trace __tracer_data = { 
	.pipe_open	= graph_trace_open,

	.close		= graph_trace_close,

	.pipe_close	= graph_trace_close,

	.wait_pipe	= poll_wait_pipe,

	.init		= graph_trace_init,

	.reset		= graph_trace_reset,

	.print_line	= print_graph_function,

kernel/trace/trace_nop.c

+0 −1
Original line number Diff line number Diff line
@@ -91,7 +91,6 @@ struct tracer nop_trace __read_mostly = 
	.name		= "nop",

	.init		= nop_trace_init,

	.reset		= nop_trace_reset,

	.wait_pipe	= poll_wait_pipe,

#ifdef CONFIG_FTRACE_SELFTEST

	.selftest	= trace_selftest_startup_nop,

#endif

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