--- /dev/null
+/*
+ * trace task wakeup timings
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
+ *
+ * Based on code from the latency_tracer, that is:
+ *
+ * Copyright (C) 2004-2006 Ingo Molnar
+ * Copyright (C) 2004 William Lee Irwin III
+ */
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+
+#include "trace.h"
+
+static struct trace_array *wakeup_trace;
+static int __read_mostly tracer_enabled;
+
+static struct task_struct *wakeup_task;
+static int wakeup_cpu;
+static unsigned wakeup_prio = -1;
+
+static DEFINE_SPINLOCK(wakeup_lock);
+
+static void notrace __wakeup_reset(struct trace_array *tr);
+
+/*
+ * Should this new latency be reported/recorded?
+ */
+static int notrace report_latency(cycle_t delta)
+{
+ if (tracing_thresh) {
+ if (delta < tracing_thresh)
+ return 0;
+ } else {
+ if (delta <= tracing_max_latency)
+ return 0;
+ }
+ return 1;
+}
+
+void notrace
+wakeup_sched_switch(struct task_struct *prev, struct task_struct *next)
+{
+ unsigned long latency = 0, t0 = 0, t1 = 0;
+ struct trace_array *tr = wakeup_trace;
+ struct trace_array_cpu *data;
+ cycle_t T0, T1, delta;
+ unsigned long flags;
+ long disabled;
+ int cpu;
+
+ if (unlikely(!tracer_enabled))
+ return;
+
+ /*
+ * When we start a new trace, we set wakeup_task to NULL
+ * and then set tracer_enabled = 1. We want to make sure
+ * that another CPU does not see the tracer_enabled = 1
+ * and the wakeup_task with an older task, that might
+ * actually be the same as next.
+ */
+ smp_rmb();
+
+ if (next != wakeup_task)
+ return;
+
+ /* The task we are waitng for is waking up */
+ data = tr->data[wakeup_cpu];
+
+ /* disable local data, not wakeup_cpu data */
+ cpu = raw_smp_processor_id();
+ disabled = atomic_inc_return(&tr->data[cpu]->disabled);
+ if (likely(disabled != 1))
+ goto out;
+
+ spin_lock_irqsave(&wakeup_lock, flags);
+
+ /* We could race with grabbing wakeup_lock */
+ if (unlikely(!tracer_enabled || next != wakeup_task))
+ goto out_unlock;
+
+ ftrace(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
+
+ /*
+ * usecs conversion is slow so we try to delay the conversion
+ * as long as possible:
+ */
+ T0 = data->preempt_timestamp;
+ T1 = now(cpu);
+ delta = T1-T0;
+
+ if (!report_latency(delta))
+ goto out_unlock;
+
+ latency = nsecs_to_usecs(delta);
+
+ tracing_max_latency = delta;
+ t0 = nsecs_to_usecs(T0);
+ t1 = nsecs_to_usecs(T1);
+
+ update_max_tr(tr, wakeup_task, wakeup_cpu);
+
+ if (tracing_thresh) {
+ printk(KERN_INFO "(%16s-%-5d|#%d): %lu us wakeup latency "
+ "violates %lu us threshold.\n"
+ " => started at timestamp %lu: ",
+ wakeup_task->comm, wakeup_task->pid,
+ raw_smp_processor_id(),
+ latency, nsecs_to_usecs(tracing_thresh), t0);
+ } else {
+ printk(KERN_INFO "(%16s-%-5d|#%d): new %lu us maximum "
+ "wakeup latency.\n => started at timestamp %lu: ",
+ wakeup_task->comm, wakeup_task->pid,
+ cpu, latency, t0);
+ }
+
+ printk(KERN_CONT " ended at timestamp %lu: ", t1);
+ dump_stack();
+ t1 = nsecs_to_usecs(now(cpu));
+ printk(KERN_CONT " dump-end timestamp %lu\n\n", t1);
+
+out_unlock:
+ __wakeup_reset(tr);
+ spin_unlock_irqrestore(&wakeup_lock, flags);
+out:
+ atomic_dec(&tr->data[cpu]->disabled);
+}
+
+static void notrace __wakeup_reset(struct trace_array *tr)
+{
+ struct trace_array_cpu *data;
+ int cpu;
+
+ assert_spin_locked(&wakeup_lock);
+
+ for_each_possible_cpu(cpu) {
+ data = tr->data[cpu];
+ tracing_reset(data);
+ }
+
+ wakeup_cpu = -1;
+ wakeup_prio = -1;
+
+ if (wakeup_task)
+ put_task_struct(wakeup_task);
+
+ wakeup_task = NULL;
+}
+
+static void notrace wakeup_reset(struct trace_array *tr)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&wakeup_lock, flags);
+ __wakeup_reset(tr);
+ spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+static notrace void
+wakeup_check_start(struct trace_array *tr, struct task_struct *p,
+ struct task_struct *curr)
+{
+ int cpu = smp_processor_id();
+ unsigned long flags;
+ long disabled;
+
+ if (likely(!rt_task(p)) ||
+ p->prio >= wakeup_prio ||
+ p->prio >= curr->prio)
+ return;
+
+ disabled = atomic_inc_return(&tr->data[cpu]->disabled);
+ if (unlikely(disabled != 1))
+ goto out;
+
+ /* interrupts should be off from try_to_wake_up */
+ spin_lock(&wakeup_lock);
+
+ /* check for races. */
+ if (!tracer_enabled || p->prio >= wakeup_prio)
+ goto out_locked;
+
+ /* reset the trace */
+ __wakeup_reset(tr);
+
+ wakeup_cpu = task_cpu(p);
+ wakeup_prio = p->prio;
+
+ wakeup_task = p;
+ get_task_struct(wakeup_task);
+
+ local_save_flags(flags);
+
+ tr->data[wakeup_cpu]->preempt_timestamp = now(cpu);
+ ftrace(tr, tr->data[wakeup_cpu], CALLER_ADDR1, CALLER_ADDR2, flags);
+
+out_locked:
+ spin_unlock(&wakeup_lock);
+out:
+ atomic_dec(&tr->data[cpu]->disabled);
+}
+
+notrace void
+ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr)
+{
+ if (likely(!tracer_enabled))
+ return;
+
+ wakeup_check_start(wakeup_trace, wakee, curr);
+}
+
+notrace void
+ftrace_wake_up_new_task(struct task_struct *wakee, struct task_struct *curr)
+{
+ if (likely(!tracer_enabled))
+ return;
+
+ wakeup_check_start(wakeup_trace, wakee, curr);
+}
+
+static notrace void start_wakeup_tracer(struct trace_array *tr)
+{
+ wakeup_reset(tr);
+
+ /*
+ * Don't let the tracer_enabled = 1 show up before
+ * the wakeup_task is reset. This may be overkill since
+ * wakeup_reset does a spin_unlock after setting the
+ * wakeup_task to NULL, but I want to be safe.
+ * This is a slow path anyway.
+ */
+ smp_wmb();
+
+ tracer_enabled = 1;
+
+ return;
+}
+
+static notrace void stop_wakeup_tracer(struct trace_array *tr)
+{
+ tracer_enabled = 0;
+}
+
+static notrace void wakeup_tracer_init(struct trace_array *tr)
+{
+ wakeup_trace = tr;
+
+ if (tr->ctrl)
+ start_wakeup_tracer(tr);
+}
+
+static notrace void wakeup_tracer_reset(struct trace_array *tr)
+{
+ if (tr->ctrl) {
+ stop_wakeup_tracer(tr);
+ /* make sure we put back any tasks we are tracing */
+ wakeup_reset(tr);
+ }
+}
+
+static void wakeup_tracer_ctrl_update(struct trace_array *tr)
+{
+ if (tr->ctrl)
+ start_wakeup_tracer(tr);
+ else
+ stop_wakeup_tracer(tr);
+}
+
+static void notrace wakeup_tracer_open(struct trace_iterator *iter)
+{
+ /* stop the trace while dumping */
+ if (iter->tr->ctrl)
+ stop_wakeup_tracer(iter->tr);
+}
+
+static void notrace wakeup_tracer_close(struct trace_iterator *iter)
+{
+ /* forget about any processes we were recording */
+ if (iter->tr->ctrl)
+ start_wakeup_tracer(iter->tr);
+}
+
+static struct tracer wakeup_tracer __read_mostly =
+{
+ .name = "wakeup",
+ .init = wakeup_tracer_init,
+ .reset = wakeup_tracer_reset,
+ .open = wakeup_tracer_open,
+ .close = wakeup_tracer_close,
+ .ctrl_update = wakeup_tracer_ctrl_update,
+ .print_max = 1,
+};
+
+__init static int init_wakeup_tracer(void)
+{
+ int ret;
+
+ ret = register_tracer(&wakeup_tracer);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+device_initcall(init_wakeup_tracer);
git.openpandora.org / pandora-kernel.git / commitdiff