tracing/ring-buffer: Only have tracing_on disable tracing buffers
As the ring-buffer code is being used by other facilities in the
kernel, having tracing_on file disable *all* buffers is not a desired
affect. It should only disable the ftrace buffers that are being used.
Move the code into the trace.c file and use the buffer disabling
for tracing_on() and tracing_off(). This way only the ftrace buffers
will be affected by them and other kernel utilities will not be
confused to why their output suddenly stopped.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 67be037..7be2e88 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -151,6 +151,9 @@
void ring_buffer_record_disable(struct ring_buffer *buffer);
void ring_buffer_record_enable(struct ring_buffer *buffer);
+void ring_buffer_record_off(struct ring_buffer *buffer);
+void ring_buffer_record_on(struct ring_buffer *buffer);
+int ring_buffer_record_is_on(struct ring_buffer *buffer);
void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index f5b7b5c..cf8d11e 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -154,35 +154,12 @@
static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
+/* Used for individual buffers (after the counter) */
+#define RB_BUFFER_OFF (1 << 20)
+
#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
/**
- * tracing_on - enable all tracing buffers
- *
- * This function enables all tracing buffers that may have been
- * disabled with tracing_off.
- */
-void tracing_on(void)
-{
- set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
-}
-EXPORT_SYMBOL_GPL(tracing_on);
-
-/**
- * tracing_off - turn off all tracing buffers
- *
- * This function stops all tracing buffers from recording data.
- * It does not disable any overhead the tracers themselves may
- * be causing. This function simply causes all recording to
- * the ring buffers to fail.
- */
-void tracing_off(void)
-{
- clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
-}
-EXPORT_SYMBOL_GPL(tracing_off);
-
-/**
* tracing_off_permanent - permanently disable ring buffers
*
* This function, once called, will disable all ring buffers
@@ -193,15 +170,6 @@
set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
}
-/**
- * tracing_is_on - show state of ring buffers enabled
- */
-int tracing_is_on(void)
-{
- return ring_buffer_flags == RB_BUFFERS_ON;
-}
-EXPORT_SYMBOL_GPL(tracing_is_on);
-
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT 4U
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
@@ -2619,6 +2587,63 @@
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
/**
+ * ring_buffer_record_off - stop all writes into the buffer
+ * @buffer: The ring buffer to stop writes to.
+ *
+ * This prevents all writes to the buffer. Any attempt to write
+ * to the buffer after this will fail and return NULL.
+ *
+ * This is different than ring_buffer_record_disable() as
+ * it works like an on/off switch, where as the disable() verison
+ * must be paired with a enable().
+ */
+void ring_buffer_record_off(struct ring_buffer *buffer)
+{
+ unsigned int rd;
+ unsigned int new_rd;
+
+ do {
+ rd = atomic_read(&buffer->record_disabled);
+ new_rd = rd | RB_BUFFER_OFF;
+ } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_off);
+
+/**
+ * ring_buffer_record_on - restart writes into the buffer
+ * @buffer: The ring buffer to start writes to.
+ *
+ * This enables all writes to the buffer that was disabled by
+ * ring_buffer_record_off().
+ *
+ * This is different than ring_buffer_record_enable() as
+ * it works like an on/off switch, where as the enable() verison
+ * must be paired with a disable().
+ */
+void ring_buffer_record_on(struct ring_buffer *buffer)
+{
+ unsigned int rd;
+ unsigned int new_rd;
+
+ do {
+ rd = atomic_read(&buffer->record_disabled);
+ new_rd = rd & ~RB_BUFFER_OFF;
+ } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_record_on);
+
+/**
+ * ring_buffer_record_is_on - return true if the ring buffer can write
+ * @buffer: The ring buffer to see if write is enabled
+ *
+ * Returns true if the ring buffer is in a state that it accepts writes.
+ */
+int ring_buffer_record_is_on(struct ring_buffer *buffer)
+{
+ return !atomic_read(&buffer->record_disabled);
+}
+
+/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
* @buffer: The ring buffer to stop writes to.
* @cpu: The CPU buffer to stop
@@ -4039,68 +4064,6 @@
}
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
-#ifdef CONFIG_TRACING
-static ssize_t
-rb_simple_read(struct file *filp, char __user *ubuf,
- size_t cnt, loff_t *ppos)
-{
- unsigned long *p = filp->private_data;
- char buf[64];
- int r;
-
- if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
- r = sprintf(buf, "permanently disabled\n");
- else
- r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
-
- return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
-}
-
-static ssize_t
-rb_simple_write(struct file *filp, const char __user *ubuf,
- size_t cnt, loff_t *ppos)
-{
- unsigned long *p = filp->private_data;
- unsigned long val;
- int ret;
-
- ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
- if (ret)
- return ret;
-
- if (val)
- set_bit(RB_BUFFERS_ON_BIT, p);
- else
- clear_bit(RB_BUFFERS_ON_BIT, p);
-
- (*ppos)++;
-
- return cnt;
-}
-
-static const struct file_operations rb_simple_fops = {
- .open = tracing_open_generic,
- .read = rb_simple_read,
- .write = rb_simple_write,
- .llseek = default_llseek,
-};
-
-
-static __init int rb_init_debugfs(void)
-{
- struct dentry *d_tracer;
-
- d_tracer = tracing_init_dentry();
-
- trace_create_file("tracing_on", 0644, d_tracer,
- &ring_buffer_flags, &rb_simple_fops);
-
- return 0;
-}
-
-fs_initcall(rb_init_debugfs);
-#endif
-
#ifdef CONFIG_HOTPLUG_CPU
static int rb_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 10d5503..f3c13d6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -352,6 +352,59 @@
static DECLARE_DELAYED_WORK(wakeup_work, wakeup_work_handler);
/**
+ * tracing_on - enable tracing buffers
+ *
+ * This function enables tracing buffers that may have been
+ * disabled with tracing_off.
+ */
+void tracing_on(void)
+{
+ if (global_trace.buffer)
+ ring_buffer_record_on(global_trace.buffer);
+ /*
+ * This flag is only looked at when buffers haven't been
+ * allocated yet. We don't really care about the race
+ * between setting this flag and actually turning
+ * on the buffer.
+ */
+ global_trace.buffer_disabled = 0;
+}
+EXPORT_SYMBOL_GPL(tracing_on);
+
+/**
+ * tracing_off - turn off tracing buffers
+ *
+ * This function stops the tracing buffers from recording data.
+ * It does not disable any overhead the tracers themselves may
+ * be causing. This function simply causes all recording to
+ * the ring buffers to fail.
+ */
+void tracing_off(void)
+{
+ if (global_trace.buffer)
+ ring_buffer_record_on(global_trace.buffer);
+ /*
+ * This flag is only looked at when buffers haven't been
+ * allocated yet. We don't really care about the race
+ * between setting this flag and actually turning
+ * on the buffer.
+ */
+ global_trace.buffer_disabled = 1;
+}
+EXPORT_SYMBOL_GPL(tracing_off);
+
+/**
+ * tracing_is_on - show state of ring buffers enabled
+ */
+int tracing_is_on(void)
+{
+ if (global_trace.buffer)
+ return ring_buffer_record_is_on(global_trace.buffer);
+ return !global_trace.buffer_disabled;
+}
+EXPORT_SYMBOL_GPL(tracing_is_on);
+
+/**
* trace_wake_up - wake up tasks waiting for trace input
*
* Schedules a delayed work to wake up any task that is blocked on the
@@ -4567,6 +4620,55 @@
create_trace_option_core_file(trace_options[i], i);
}
+static ssize_t
+rb_simple_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct ring_buffer *buffer = filp->private_data;
+ char buf[64];
+ int r;
+
+ if (buffer)
+ r = ring_buffer_record_is_on(buffer);
+ else
+ r = 0;
+
+ r = sprintf(buf, "%d\n", r);
+
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+rb_simple_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ struct ring_buffer *buffer = filp->private_data;
+ unsigned long val;
+ int ret;
+
+ ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+ if (ret)
+ return ret;
+
+ if (buffer) {
+ if (val)
+ ring_buffer_record_on(buffer);
+ else
+ ring_buffer_record_off(buffer);
+ }
+
+ (*ppos)++;
+
+ return cnt;
+}
+
+static const struct file_operations rb_simple_fops = {
+ .open = tracing_open_generic,
+ .read = rb_simple_read,
+ .write = rb_simple_write,
+ .llseek = default_llseek,
+};
+
static __init int tracer_init_debugfs(void)
{
struct dentry *d_tracer;
@@ -4626,6 +4728,9 @@
trace_create_file("trace_clock", 0644, d_tracer, NULL,
&trace_clock_fops);
+ trace_create_file("tracing_on", 0644, d_tracer,
+ global_trace.buffer, &rb_simple_fops);
+
#ifdef CONFIG_DYNAMIC_FTRACE
trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
&ftrace_update_tot_cnt, &tracing_dyn_info_fops);
@@ -4863,6 +4968,8 @@
goto out_free_cpumask;
}
global_trace.entries = ring_buffer_size(global_trace.buffer);
+ if (global_trace.buffer_disabled)
+ tracing_off();
#ifdef CONFIG_TRACER_MAX_TRACE
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 54faec7..ce887c0 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -154,6 +154,7 @@
struct ring_buffer *buffer;
unsigned long entries;
int cpu;
+ int buffer_disabled;
cycle_t time_start;
struct task_struct *waiter;
struct trace_array_cpu *data[NR_CPUS];