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tracing: Remove mock up poll wait function

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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: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2014-04-29 17:54:37 -04:00 committed by Steven Rostedt
parent f487426104
commit b1169cc69b
6 changed files with 4 additions and 34 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

29
kernel/trace/trace.c
View file

@ -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;

4
kernel/trace/trace.h
View file

@ -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,

1
kernel/trace/trace_functions.c
View file

@ -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,

1
kernel/trace/trace_functions_graph.c
View file

@ -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,

1
kernel/trace/trace_nop.c
View file

@ -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

2
kernel/trace/trace_sched_wakeup.c
View file

@ -705,7 +705,6 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.reset = wakeup_tracer_reset,
.start = wakeup_tracer_start,
.stop = wakeup_tracer_stop,
.wait_pipe = poll_wait_pipe,
.print_max = true,
.print_header = wakeup_print_header,
.print_line = wakeup_print_line,
@ -728,7 +727,6 @@ static struct tracer wakeup_dl_tracer __read_mostly =
.reset = wakeup_tracer_reset,
.start = wakeup_tracer_start,
.stop = wakeup_tracer_stop,
.wait_pipe = poll_wait_pipe,
.print_max = true,
.print_header = wakeup_print_header,
.print_line = wakeup_print_line,