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Subject[RFC PATCH 07/30 v3] tracer add debugfs interface
This patch adds an interface into debugfs.

/debugfs/tracing/ctrl

echoing 1 into the ctrl file turns on the tracer,
and echoing 0 turns it off.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
lib/tracing/tracer.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++-
lib/tracing/tracer.h | 1
2 files changed, 87 insertions(+), 1 deletion(-)

Index: linux-compile.git/lib/tracing/tracer.c
===================================================================
--- linux-compile.git.orig/lib/tracing/tracer.c 2008-01-14 13:14:13.000000000 -0500
+++ linux-compile.git/lib/tracing/tracer.c 2008-01-14 14:57:59.000000000 -0500
@@ -15,6 +15,8 @@
#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/seq_file.h>
+#include <linux/debugfs.h>
+#include <linux/uaccess.h>
#include <linux/mcount.h>

#include "tracer.h"
@@ -58,9 +60,12 @@ static notrace void trace_function(const
int cpu;

raw_local_irq_save(flags);
- cpu = raw_smp_processor_id();

tr = &mctracer_trace;
+ if (!tr->ctrl)
+ goto out;
+
+ cpu = raw_smp_processor_id();

atomic_inc(&tr->disabled[cpu]);
if (likely(atomic_read(&tr->disabled[cpu]) == 1))
@@ -68,6 +73,7 @@ static notrace void trace_function(const

atomic_dec(&tr->disabled[cpu]);

+ out:
raw_local_irq_restore(flags);
}

@@ -76,6 +82,83 @@ static struct mcount_ops trace_ops __rea
.func = trace_function,
};

+#ifdef CONFIG_DEBUG_FS
+static int mctracer_open_generic(struct inode *inode, struct file *filp)
+{
+ filp->private_data = inode->i_private;
+ return 0;
+}
+
+
+static ssize_t mctracer_ctrl_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct mctracer_trace *tr = filp->private_data;
+ char buf[16];
+ int r;
+
+ r = sprintf(buf, "%ld\n", tr->ctrl);
+ return simple_read_from_buffer(ubuf, cnt, ppos,
+ buf, r);
+}
+
+static ssize_t mctracer_ctrl_write(struct file *filp,
+ const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct mctracer_trace *tr = filp->private_data;
+ long val;
+ char buf[16];
+
+ if (cnt > 15)
+ cnt = 15;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+
+ val = !!simple_strtoul(buf, NULL, 10);
+
+ tr->ctrl = val;
+
+ filp->f_pos += cnt;
+
+ return cnt;
+}
+
+static struct file_operations mctracer_ctrl_fops = {
+ .open = mctracer_open_generic,
+ .read = mctracer_ctrl_read,
+ .write = mctracer_ctrl_write,
+};
+
+static void mctrace_init_debugfs(void)
+{
+ struct dentry *d_mctracer;
+ struct dentry *entry;
+
+ d_mctracer = debugfs_create_dir("tracing", NULL);
+ if (!d_mctracer) {
+ pr_warning("Could not create debugfs directory mctracer\n");
+ return;
+ }
+
+ entry = debugfs_create_file("ctrl", 0644, d_mctracer,
+ &mctracer_trace, &mctracer_ctrl_fops);
+ if (!entry)
+ pr_warning("Could not create debugfs 'ctrl' entry\n");
+}
+#else /* CONFIG_DEBUG_FS */
+static void mctrace_init_debugfs(void)
+{
+ /*
+ * No way to turn on or off the trace function
+ * without debugfs.
+ */
+}
+#endif /* CONFIG_DEBUG_FS */
+
static notrace int page_order(const unsigned long size)
{
const unsigned long nr_pages = DIV_ROUND_UP(size, PAGE_SIZE);
@@ -112,6 +195,8 @@ static notrace int mctracer_alloc_buffer

register_mcount_function(&trace_ops);

+ mctrace_init_debugfs();
+
return 0;

free_buffers:
Index: linux-compile.git/lib/tracing/tracer.h
===================================================================
--- linux-compile.git.orig/lib/tracing/tracer.h 2008-01-14 13:14:13.000000000 -0500
+++ linux-compile.git/lib/tracing/tracer.h 2008-01-14 14:57:58.000000000 -0500
@@ -13,6 +13,7 @@ struct mctracer_trace {
void *trace[NR_CPUS];
unsigned long trace_idx[NR_CPUS];
unsigned long entries;
+ long ctrl;
atomic_t cnt;
atomic_t disabled[NR_CPUS];
atomic_t underrun[NR_CPUS];
--


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