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>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e058c60..4c392c8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1085,7 +1085,7 @@
}
#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 @@
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 @@
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 @@
mutex_unlock(&iter->mutex);
- iter->trace->wait_pipe(iter);
+ wait_on_pipe(iter);
mutex_lock(&iter->mutex);
@@ -5179,7 +5158,7 @@
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 @@
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;