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Subject[PATCH 16/23 -v6] trace generic call to schedule switch
This patch adds hooks into the schedule switch tracing to
allow other latency traces to hook into the schedule switches.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
lib/tracing/trace_sched_switch.c | 123 +++++++++++++++++++++++++++++++++------
lib/tracing/tracer.h | 14 ++++
2 files changed, 119 insertions(+), 18 deletions(-)
Index: linux-mcount.git/lib/tracing/tracer.h
===================================================================
--- linux-mcount.git.orig/lib/tracing/tracer.h 2008-01-25 21:47:25.000000000 -0500
+++ linux-mcount.git/lib/tracing/tracer.h 2008-01-25 21:47:27.000000000 -0500
@@ -112,4 +112,18 @@ static inline notrace cycle_t now(void)
return get_monotonic_cycles();
}

+#ifdef CONFIG_CONTEXT_SWITCH_TRACER
+typedef void (*tracer_switch_func_t)(void *private,
+ struct task_struct *prev,
+ struct task_struct *next);
+struct tracer_switch_ops {
+ tracer_switch_func_t func;
+ void *private;
+ struct tracer_switch_ops *next;
+};
+
+extern int register_tracer_switch(struct tracer_switch_ops *ops);
+extern int unregister_tracer_switch(struct tracer_switch_ops *ops);
+#endif /* CONFIG_CONTEXT_SWITCH_TRACER */
+
#endif /* _LINUX_MCOUNT_TRACER_H */
Index: linux-mcount.git/lib/tracing/trace_sched_switch.c
===================================================================
--- linux-mcount.git.orig/lib/tracing/trace_sched_switch.c 2008-01-25 21:47:25.000000000 -0500
+++ linux-mcount.git/lib/tracing/trace_sched_switch.c 2008-01-25 21:47:27.000000000 -0500
@@ -16,33 +16,21 @@

static struct tracing_trace *tracer_trace;
static int trace_enabled __read_mostly;
+static DEFINE_SPINLOCK(sched_switch_func_lock);

-static notrace void sched_switch_callback(const struct marker *mdata,
- void *private_data,
- const char *format, ...)
+static void notrace sched_switch_func(void *private,
+ struct task_struct *prev,
+ struct task_struct *next)
{
- struct tracing_trace **p = mdata->private;
- struct tracing_trace *tr = *p;
+ struct tracing_trace **ptr = private;
+ struct tracing_trace *tr = *ptr;
struct tracing_trace_cpu *data;
- struct task_struct *prev;
- struct task_struct *next;
unsigned long flags;
- va_list ap;
int cpu;

- if (likely(!atomic_read(&trace_record_cmdline)))
- return;
-
- tracing_record_cmdline(current);
-
if (likely(!trace_enabled))
return;

- va_start(ap, format);
- prev = va_arg(ap, typeof(prev));
- next = va_arg(ap, typeof(next));
- va_end(ap);
-
raw_local_irq_save(flags);
cpu = raw_smp_processor_id();
data = tr->data[cpu];
@@ -55,6 +43,105 @@ static notrace void sched_switch_callbac
raw_local_irq_restore(flags);
}

+static struct tracer_switch_ops sched_switch_ops __read_mostly =
+{
+ .func = sched_switch_func,
+ .private = &tracer_trace,
+};
+
+static tracer_switch_func_t tracer_switch_func __read_mostly =
+ sched_switch_func;
+
+static struct tracer_switch_ops *tracer_switch_func_ops __read_mostly =
+ &sched_switch_ops;
+
+static void notrace sched_switch_func_loop(void *private,
+ struct task_struct *prev,
+ struct task_struct *next)
+{
+ struct tracer_switch_ops *ops = tracer_switch_func_ops;
+
+ for (; ops != NULL; ops = ops->next)
+ ops->func(ops->private, prev, next);
+}
+
+notrace int register_tracer_switch(struct tracer_switch_ops *ops)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&sched_switch_func_lock, flags);
+ ops->next = tracer_switch_func_ops;
+ smp_wmb();
+ tracer_switch_func_ops = ops;
+
+ if (ops->next == &sched_switch_ops)
+ tracer_switch_func = sched_switch_func_loop;
+
+ spin_unlock_irqrestore(&sched_switch_func_lock, flags);
+
+ return 0;
+}
+
+notrace int unregister_tracer_switch(struct tracer_switch_ops *ops)
+{
+ unsigned long flags;
+ struct tracer_switch_ops **p = &tracer_switch_func_ops;
+ int ret;
+
+ spin_lock_irqsave(&sched_switch_func_lock, flags);
+
+ /*
+ * If the sched_switch is the only one left, then
+ * only call that function.
+ */
+ if (*p == ops && ops->next == &sched_switch_ops) {
+ tracer_switch_func = sched_switch_func;
+ tracer_switch_func_ops = &sched_switch_ops;
+ goto out;
+ }
+
+ for (; *p != &sched_switch_ops; p = &(*p)->next)
+ if (*p == ops)
+ break;
+
+ if (*p != ops) {
+ ret = -1;
+ goto out;
+ }
+
+ *p = (*p)->next;
+
+ out:
+ spin_unlock_irqrestore(&sched_switch_func_lock, flags);
+
+ return 0;
+}
+
+static notrace void sched_switch_callback(const struct marker *mdata,
+ void *private_data,
+ const char *format, ...)
+{
+ struct task_struct *prev;
+ struct task_struct *next;
+ va_list ap;
+
+ if (likely(!atomic_read(&trace_record_cmdline)))
+ return;
+
+ tracing_record_cmdline(current);
+
+ va_start(ap, format);
+ prev = va_arg(ap, typeof(prev));
+ next = va_arg(ap, typeof(next));
+ va_end(ap);
+
+ /*
+ * If tracer_switch_func only points to the local
+ * switch func, it still needs the ptr passed to it.
+ */
+ tracer_switch_func(mdata->private, prev, next);
+}
+
static notrace void sched_switch_reset(struct tracing_trace *tr)
{
int cpu;
--


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