From b1169cc69ba96b124df820904a6d3eb775491d7f Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" 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 Signed-off-by: Steven Rostedt --- 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 e058c6091e45..4c392c8238bf 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 8624b5041466..3b3e09e61f33 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 2d9482b8f26a..57f0ec962d2c 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 deff11200261..b86dd4d8c6a6 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 69a5cc94c01a..fcf0a9e48916 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 1573c03640d2..19bd8928ce94 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, -- 2.20.1