Commit f536aafc authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
Browse files

ring-buffer: replace most bug ons with warn on and disable buffer 



This patch replaces most of the BUG_ONs in the ring_buffer code with
RB_WARN_ON variants. It adds some more variants as needed for the
replacement. This lets the buffer die nicely and still warn the user.

One BUG_ON remains in the code, and that is because it detects a
bad pointer passed in by the calling function, and not a bug by
the ring buffer code itself.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 5aa1ba6a

kernel/trace/ring_buffer.c

+49 −16
Original line number Diff line number Diff line
@@ -188,6 +188,7 @@ struct ring_buffer_iter { 
	u64				read_stamp;

};



/* buffer may be either ring_buffer or ring_buffer_per_cpu */

#define RB_WARN_ON(buffer, cond)				\

	do {							\

		if (unlikely(cond)) {				\
@@ -197,6 +198,15 @@ struct ring_buffer_iter { 
	} while (0)



#define RB_WARN_ON_RET(buffer, cond)				\

	do {							\

		if (unlikely(cond)) {				\

			atomic_inc(&buffer->record_disabled);	\

			WARN_ON(1);				\

			return;					\

		}						\

	} while (0)



#define RB_WARN_ON_RET_INT(buffer, cond)			\

	do {							\

		if (unlikely(cond)) {				\

			atomic_inc(&buffer->record_disabled);	\
@@ -205,6 +215,15 @@ struct ring_buffer_iter { 
		}						\

	} while (0)



#define RB_WARN_ON_RET_NULL(buffer, cond)			\

	do {							\

		if (unlikely(cond)) {				\

			atomic_inc(&buffer->record_disabled);	\

			WARN_ON(1);				\

			return NULL;				\

		}						\

	} while (0)



#define RB_WARN_ON_ONCE(buffer, cond)				\

	do {							\

		static int once;				\
@@ -215,6 +234,17 @@ struct ring_buffer_iter { 
		}						\

	} while (0)



/* buffer must be ring_buffer not per_cpu */

#define RB_WARN_ON_UNLOCK(buffer, cond)				\

	do {							\

		if (unlikely(cond)) {				\

			mutex_unlock(&buffer->mutex);		\

			atomic_inc(&buffer->record_disabled);	\

			WARN_ON(1);				\

			return -1;				\

		}						\

	} while (0)



/**

 * check_pages - integrity check of buffer pages

 * @cpu_buffer: CPU buffer with pages to test
@@ -227,13 +257,13 @@ static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) 
	struct list_head *head = &cpu_buffer->pages;

	struct buffer_page *page, *tmp;



	RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);

	RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);

	RB_WARN_ON_RET_INT(cpu_buffer, head->next->prev != head);

	RB_WARN_ON_RET_INT(cpu_buffer, head->prev->next != head);



	list_for_each_entry_safe(page, tmp, head, list) {

		RB_WARN_ON_RET(cpu_buffer,

		RB_WARN_ON_RET_INT(cpu_buffer,

			       page->list.next->prev != &page->list);

		RB_WARN_ON_RET(cpu_buffer,

		RB_WARN_ON_RET_INT(cpu_buffer,

			       page->list.prev->next != &page->list);

	}
@@ -440,13 +470,13 @@ rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages) 
	synchronize_sched();



	for (i = 0; i < nr_pages; i++) {

		BUG_ON(list_empty(&cpu_buffer->pages));

		RB_WARN_ON_RET(cpu_buffer, list_empty(&cpu_buffer->pages));

		p = cpu_buffer->pages.next;

		page = list_entry(p, struct buffer_page, list);

		list_del_init(&page->list);

		free_buffer_page(page);

	}

	BUG_ON(list_empty(&cpu_buffer->pages));

	RB_WARN_ON_RET(cpu_buffer, list_empty(&cpu_buffer->pages));



	rb_reset_cpu(cpu_buffer);
@@ -468,7 +498,7 @@ rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer, 
	synchronize_sched();



	for (i = 0; i < nr_pages; i++) {

		BUG_ON(list_empty(pages));

		RB_WARN_ON_RET(cpu_buffer, list_empty(pages));

		p = pages->next;

		page = list_entry(p, struct buffer_page, list);

		list_del_init(&page->list);
@@ -523,7 +553,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) 
	if (size < buffer_size) {



		/* easy case, just free pages */

		BUG_ON(nr_pages >= buffer->pages);

		RB_WARN_ON_UNLOCK(buffer, nr_pages >= buffer->pages);



		rm_pages = buffer->pages - nr_pages;
@@ -542,7 +572,8 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) 
	 * add these pages to the cpu_buffers. Otherwise we just free

	 * them all and return -ENOMEM;

	 */

	BUG_ON(nr_pages <= buffer->pages);

	RB_WARN_ON_UNLOCK(buffer, nr_pages <= buffer->pages);



	new_pages = nr_pages - buffer->pages;



	for_each_buffer_cpu(buffer, cpu) {
@@ -565,7 +596,7 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size) 
		rb_insert_pages(cpu_buffer, &pages, new_pages);

	}



	BUG_ON(!list_empty(&pages));

	RB_WARN_ON_UNLOCK(buffer, !list_empty(&pages));



 out:

	buffer->pages = nr_pages;
@@ -653,7 +684,7 @@ static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer) 
	     head += rb_event_length(event)) {



		event = __rb_page_index(cpu_buffer->head_page, head);

		BUG_ON(rb_null_event(event));

		RB_WARN_ON_RET(cpu_buffer, rb_null_event(event));

		/* Only count data entries */

		if (event->type != RINGBUF_TYPE_DATA)

			continue;
@@ -940,7 +971,7 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, 


	/* We reserved something on the buffer */



	BUG_ON(write > BUF_PAGE_SIZE);

	RB_WARN_ON_RET_NULL(cpu_buffer, write > BUF_PAGE_SIZE);



	event = __rb_page_index(tail_page, tail);

	rb_update_event(event, type, length);
@@ -1621,7 +1652,7 @@ static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer) 
	reader = rb_get_reader_page(cpu_buffer);



	/* This function should not be called when buffer is empty */

	BUG_ON(!reader);

	RB_WARN_ON_RET(cpu_buffer, !reader);



	event = rb_reader_event(cpu_buffer);
@@ -1648,7 +1679,8 @@ static void rb_advance_iter(struct ring_buffer_iter *iter) 
	 * Check if we are at the end of the buffer.

	 */

	if (iter->head >= rb_page_size(iter->head_page)) {

		BUG_ON(iter->head_page == cpu_buffer->commit_page);

		RB_WARN_ON_RET(buffer,

			       iter->head_page == cpu_buffer->commit_page);

		rb_inc_iter(iter);

		return;

	}
@@ -1661,7 +1693,8 @@ static void rb_advance_iter(struct ring_buffer_iter *iter) 
	 * This should not be called to advance the header if we are

	 * at the tail of the buffer.

	 */

	BUG_ON((iter->head_page == cpu_buffer->commit_page) &&

	RB_WARN_ON_RET(cpu_buffer,

		       (iter->head_page == cpu_buffer->commit_page) &&

		       (iter->head + length > rb_commit_index(cpu_buffer)));



	rb_update_iter_read_stamp(iter, event);

CRA Git | Maintained and supported by SUSTech CRA and CCSE