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>
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@ -1085,7 +1085,7 @@ update_max_tr_single(struct trace_array *tr, struct task_struct *tsk, int cpu)
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}
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#endif /* CONFIG_TRACER_MAX_TRACE */
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static void default_wait_pipe(struct trace_iterator *iter)
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static void wait_on_pipe(struct trace_iterator *iter)
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{
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/* Iterators are static, they should be filled or empty */
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if (trace_buffer_iter(iter, iter->cpu_file))
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@ -1202,8 +1202,6 @@ int register_tracer(struct tracer *type)
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else
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if (!type->flags->opts)
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type->flags->opts = dummy_tracer_opt;
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if (!type->wait_pipe)
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type->wait_pipe = default_wait_pipe;
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ret = run_tracer_selftest(type);
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if (ret < 0)
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@ -4207,25 +4205,6 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table)
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return trace_poll(iter, filp, poll_table);
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}
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/*
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* This is a make-shift waitqueue.
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* A tracer might use this callback on some rare cases:
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*
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* 1) the current tracer might hold the runqueue lock when it wakes up
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* a reader, hence a deadlock (sched, function, and function graph tracers)
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* 2) the function tracers, trace all functions, we don't want
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* the overhead of calling wake_up and friends
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* (and tracing them too)
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*
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* Anyway, this is really very primitive wakeup.
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*/
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void poll_wait_pipe(struct trace_iterator *iter)
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{
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set_current_state(TASK_INTERRUPTIBLE);
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/* sleep for 100 msecs, and try again. */
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schedule_timeout(HZ / 10);
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}
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/* Must be called with trace_types_lock mutex held. */
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static int tracing_wait_pipe(struct file *filp)
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{
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@ -4251,7 +4230,7 @@ static int tracing_wait_pipe(struct file *filp)
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mutex_unlock(&iter->mutex);
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iter->trace->wait_pipe(iter);
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wait_on_pipe(iter);
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mutex_lock(&iter->mutex);
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@ -5179,7 +5158,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
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goto out_unlock;
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}
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mutex_unlock(&trace_types_lock);
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iter->trace->wait_pipe(iter);
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wait_on_pipe(iter);
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mutex_lock(&trace_types_lock);
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if (signal_pending(current)) {
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size = -EINTR;
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@ -5390,7 +5369,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
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goto out;
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}
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mutex_unlock(&trace_types_lock);
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iter->trace->wait_pipe(iter);
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wait_on_pipe(iter);
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mutex_lock(&trace_types_lock);
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if (signal_pending(current)) {
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ret = -EINTR;
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@ -338,7 +338,6 @@ struct tracer_flags {
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* @stop: called when tracing is paused (echo 0 > tracing_enabled)
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* @open: called when the trace file is opened
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* @pipe_open: called when the trace_pipe file is opened
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* @wait_pipe: override how the user waits for traces on trace_pipe
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* @close: called when the trace file is released
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* @pipe_close: called when the trace_pipe file is released
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* @read: override the default read callback on trace_pipe
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@ -357,7 +356,6 @@ struct tracer {
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void (*stop)(struct trace_array *tr);
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void (*open)(struct trace_iterator *iter);
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void (*pipe_open)(struct trace_iterator *iter);
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void (*wait_pipe)(struct trace_iterator *iter);
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void (*close)(struct trace_iterator *iter);
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void (*pipe_close)(struct trace_iterator *iter);
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ssize_t (*read)(struct trace_iterator *iter,
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@ -566,8 +564,6 @@ void trace_init_global_iter(struct trace_iterator *iter);
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void tracing_iter_reset(struct trace_iterator *iter, int cpu);
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void poll_wait_pipe(struct trace_iterator *iter);
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void tracing_sched_switch_trace(struct trace_array *tr,
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struct task_struct *prev,
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struct task_struct *next,
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@ -252,7 +252,6 @@ static struct tracer function_trace __tracer_data =
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.init = function_trace_init,
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.reset = function_trace_reset,
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.start = function_trace_start,
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.wait_pipe = poll_wait_pipe,
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.flags = &func_flags,
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.set_flag = func_set_flag,
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.allow_instances = true,
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@ -1505,7 +1505,6 @@ static struct tracer graph_trace __tracer_data = {
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.pipe_open = graph_trace_open,
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.close = graph_trace_close,
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.pipe_close = graph_trace_close,
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.wait_pipe = poll_wait_pipe,
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.init = graph_trace_init,
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.reset = graph_trace_reset,
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.print_line = print_graph_function,
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@ -91,7 +91,6 @@ struct tracer nop_trace __read_mostly =
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.name = "nop",
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.init = nop_trace_init,
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.reset = nop_trace_reset,
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.wait_pipe = poll_wait_pipe,
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#ifdef CONFIG_FTRACE_SELFTEST
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.selftest = trace_selftest_startup_nop,
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#endif
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@ -705,7 +705,6 @@ static struct tracer wakeup_rt_tracer __read_mostly =
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.reset = wakeup_tracer_reset,
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.start = wakeup_tracer_start,
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.stop = wakeup_tracer_stop,
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.wait_pipe = poll_wait_pipe,
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.print_max = true,
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.print_header = wakeup_print_header,
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.print_line = wakeup_print_line,
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@ -728,7 +727,6 @@ static struct tracer wakeup_dl_tracer __read_mostly =
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.reset = wakeup_tracer_reset,
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.start = wakeup_tracer_start,
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.stop = wakeup_tracer_stop,
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.wait_pipe = poll_wait_pipe,
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.print_max = true,
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.print_header = wakeup_print_header,
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.print_line = wakeup_print_line,
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