7e6ea92df3
Impact: display events when they arrive Now that the events don't use wake_up() anymore, we need the nop tracer to poll waiting for events on the pipe. Especially because nop is useful to look at orphan traces types (traces types that don't rely on specific tracers) because it doesn't produce traces itself. And unlike other tracers that trigger specific traces periodically, nop triggers no traces by itself that can wake him. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <1237759847-21025-5-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
102 lines
2.2 KiB
C
102 lines
2.2 KiB
C
/*
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* nop tracer
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*
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* Copyright (C) 2008 Steven Noonan <steven@uplinklabs.net>
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*
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/debugfs.h>
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#include <linux/ftrace.h>
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#include "trace.h"
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/* Our two options */
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enum {
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TRACE_NOP_OPT_ACCEPT = 0x1,
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TRACE_NOP_OPT_REFUSE = 0x2
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};
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/* Options for the tracer (see trace_options file) */
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static struct tracer_opt nop_opts[] = {
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/* Option that will be accepted by set_flag callback */
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{ TRACER_OPT(test_nop_accept, TRACE_NOP_OPT_ACCEPT) },
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/* Option that will be refused by set_flag callback */
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{ TRACER_OPT(test_nop_refuse, TRACE_NOP_OPT_REFUSE) },
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{ } /* Always set a last empty entry */
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};
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static struct tracer_flags nop_flags = {
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/* You can check your flags value here when you want. */
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.val = 0, /* By default: all flags disabled */
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.opts = nop_opts
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};
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static struct trace_array *ctx_trace;
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static void start_nop_trace(struct trace_array *tr)
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{
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/* Nothing to do! */
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}
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static void stop_nop_trace(struct trace_array *tr)
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{
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/* Nothing to do! */
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}
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static int nop_trace_init(struct trace_array *tr)
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{
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ctx_trace = tr;
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start_nop_trace(tr);
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return 0;
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}
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static void nop_trace_reset(struct trace_array *tr)
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{
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stop_nop_trace(tr);
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}
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/* It only serves as a signal handler and a callback to
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* accept or refuse tthe setting of a flag.
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* If you don't implement it, then the flag setting will be
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* automatically accepted.
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*/
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static int nop_set_flag(u32 old_flags, u32 bit, int set)
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{
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/*
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* Note that you don't need to update nop_flags.val yourself.
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* The tracing Api will do it automatically if you return 0
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*/
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if (bit == TRACE_NOP_OPT_ACCEPT) {
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printk(KERN_DEBUG "nop_test_accept flag set to %d: we accept."
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" Now cat trace_options to see the result\n",
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set);
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return 0;
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}
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if (bit == TRACE_NOP_OPT_REFUSE) {
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printk(KERN_DEBUG "nop_test_refuse flag set to %d: we refuse."
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"Now cat trace_options to see the result\n",
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set);
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return -EINVAL;
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}
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return 0;
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}
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struct tracer nop_trace __read_mostly =
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{
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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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.flags = &nop_flags,
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.set_flag = nop_set_flag
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};
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