Commit b2e7c6ed authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
Browse files

ring-buffer: Simplify ring_buffer_read_page() with guard() 

The function ring_buffer_read_page() had two gotos. One was simply
returning "ret" and the other was unlocking the reader_lock.

There's no reason to use goto to simply return the "ret" variable. Instead
just return the value.

The jump to the unlocking of the reader_lock can be replaced by
guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock).

With these two changes the "ret" variable is no longer used and can be
removed. The return value on non-error is what was read and is stored in
the "read" variable.

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250527145216.0187cf36@gandalf.local.home


Reviewed-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent f0d8cbc8

kernel/trace/ring_buffer.c

+11 −17
Original line number Diff line number Diff line
@@ -6531,38 +6531,37 @@ int ring_buffer_read_page(struct trace_buffer *buffer, 
	struct buffer_data_page *bpage;

	struct buffer_page *reader;

	unsigned long missed_events;

	unsigned long flags;

	unsigned int commit;

	unsigned int read;

	u64 save_timestamp;

	int ret = -1;



	if (!cpumask_test_cpu(cpu, buffer->cpumask))

		goto out;

		return -1;



	/*

	 * If len is not big enough to hold the page header, then

	 * we can not copy anything.

	 */

	if (len <= BUF_PAGE_HDR_SIZE)

		goto out;

		return -1;



	len -= BUF_PAGE_HDR_SIZE;



	if (!data_page || !data_page->data)

		goto out;

		return -1;



	if (data_page->order != buffer->subbuf_order)

		goto out;

		return -1;



	bpage = data_page->data;

	if (!bpage)

		goto out;

		return -1;



	raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);

	guard(raw_spinlock_irqsave)(&cpu_buffer->reader_lock);



	reader = rb_get_reader_page(cpu_buffer);

	if (!reader)

		goto out_unlock;

		return -1;



	event = rb_reader_event(cpu_buffer);
@@ -6596,7 +6595,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer, 
		if (full &&

		    (!read || (len < (commit - read)) ||

		     cpu_buffer->reader_page == cpu_buffer->commit_page))

			goto out_unlock;

			return -1;



		if (len > (commit - read))

			len = (commit - read);
@@ -6605,7 +6604,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer, 
		size = rb_event_ts_length(event);



		if (len < size)

			goto out_unlock;

			return -1;



		/* save the current timestamp, since the user will need it */

		save_timestamp = cpu_buffer->read_stamp;
@@ -6663,7 +6662,6 @@ int ring_buffer_read_page(struct trace_buffer *buffer, 
		if (reader->real_end)

			local_set(&bpage->commit, reader->real_end);

	}

	ret = read;



	cpu_buffer->lost_events = 0;
@@ -6690,11 +6688,7 @@ int ring_buffer_read_page(struct trace_buffer *buffer, 
	if (commit < buffer->subbuf_size)

		memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);



 out_unlock:

	raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);



 out:

	return ret;

	return read;

}

EXPORT_SYMBOL_GPL(ring_buffer_read_page);