Commit 9af4ab0e authored by Vincent Donnefort's avatar Vincent Donnefort Committed by Steven Rostedt (Google)
Browse files

tracing: Add reset to trace remotes 

Allow to reset the trace remote buffer by writing to the Tracefs "trace"
file. This is similar to the regular Tracefs interface.

Link: https://patch.msgid.link/20260309162516.2623589-7-vdonnefort@google.com


Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarVincent Donnefort <vdonnefort@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 96e43537

include/linux/trace_remote.h

+3 −0
Original line number Diff line number Diff line
@@ -17,6 +17,8 @@ 
 *			remote to allow writing.

 * @swap_reader_page:	Called when Tracefs consumes a new page from a

 *			ring-buffer. It is expected from the remote to isolate a

 * @reset:		Called on `echo 0 > trace`. It is expected from the

 *			remote to reset all ring-buffer pages.

 *			new reader-page from the @cpu ring-buffer.

 */

struct trace_remote_callbacks {
@@ -24,6 +26,7 @@ struct trace_remote_callbacks { 
	void	(*unload_trace_buffer)(struct trace_buffer_desc *desc, void *priv);

	int	(*enable_tracing)(bool enable, void *priv);

	int	(*swap_reader_page)(unsigned int cpu, void *priv);

	int	(*reset)(unsigned int cpu, void *priv);

};



int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv);

kernel/trace/trace_remote.c

+45 −0
Original line number Diff line number Diff line
@@ -63,6 +63,7 @@ static int trace_remote_load(struct trace_remote *remote) 
	rb_remote->desc = desc;

	rb_remote->swap_reader_page = remote->cbs->swap_reader_page;

	rb_remote->priv = remote->priv;

	rb_remote->reset = remote->cbs->reset;

	remote->trace_buffer = ring_buffer_alloc_remote(rb_remote);

	if (!remote->trace_buffer) {

		remote->cbs->unload_trace_buffer(desc, remote->priv);
@@ -138,6 +139,21 @@ static int trace_remote_disable_tracing(struct trace_remote *remote) 
	return 0;

}



static void trace_remote_reset(struct trace_remote *remote, int cpu)

{

	lockdep_assert_held(&remote->lock);



	if (!trace_remote_loaded(remote))

		return;



	if (cpu == RING_BUFFER_ALL_CPUS)

		ring_buffer_reset(remote->trace_buffer);

	else

		ring_buffer_reset_cpu(remote->trace_buffer, cpu);



	trace_remote_try_unload(remote);

}



static ssize_t

tracing_on_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos)

{
@@ -414,6 +430,26 @@ static const struct file_operations trace_pipe_fops = { 
	.release	= trace_pipe_release,

};



static ssize_t trace_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos)

{

	struct inode *inode = file_inode(filp);

	struct trace_remote *remote = inode->i_private;

	int cpu = RING_BUFFER_ALL_CPUS;



	if (inode->i_cdev)

		cpu = (long)inode->i_cdev - 1;



	guard(mutex)(&remote->lock);



	trace_remote_reset(remote, cpu);



	return cnt;

}



static const struct file_operations trace_fops = {

	.write		= trace_write,

};



static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote)

{

	struct dentry *remote_d, *percpu_d, *d;
@@ -452,6 +488,10 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo 
	if (!d)

		goto err;



	d = trace_create_file("trace", TRACEFS_MODE_WRITE, remote_d, remote, &trace_fops);

	if (!d)

		goto err;



	percpu_d = tracefs_create_dir("per_cpu", remote_d);

	if (!percpu_d) {

		pr_err("Failed to create tracefs dir "TRACEFS_DIR"%s/per_cpu/\n", name);
@@ -474,6 +514,11 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo 
					  &trace_pipe_fops);

		if (!d)

			goto err;



		d = trace_create_cpu_file("trace", TRACEFS_MODE_WRITE, cpu_d, remote, cpu,

					  &trace_fops);

		if (!d)

			goto err;

	}



	return 0;