From b1169cc69ba96b124df820904a6d3eb775491d7f Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
Date: Tue, 29 Apr 2014 17:54:37 -0400
Subject: [PATCH] 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: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 29 ++++------------------------
kernel/trace/trace.h | 4 ----
kernel/trace/trace_functions.c | 1 -
kernel/trace/trace_functions_graph.c | 1 -
kernel/trace/trace_nop.c | 1 -
kernel/trace/trace_sched_wakeup.c | 2 --
6 files changed, 4 insertions(+), 34 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e058c6091e454..4c392c8238bf9 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8624b50414660..3b3e09e61f338 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -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,
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 2d9482b8f26a2..57f0ec962d2ca 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -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,
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index deff11200261b..b86dd4d8c6a67 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -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,
diff --git a/kernel/trace/trace_nop.c b/kernel/trace/trace_nop.c
index 69a5cc94c01a3..fcf0a9e489162 100644
--- a/kernel/trace/trace_nop.c
+++ b/kernel/trace/trace_nop.c
@@ -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
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 1573c03640d23..19bd8928ce944 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -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,
--
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