[PATCH 2/2] ring-buffer: replace most bug ons with warn on and disable buffer

Steven Rostedt
2008-11-11T04:12:53Z

[-- Attachment #1: 0002-ring-buffer-replace-most-bug-ons-with-warn-on-and-d.patch --]
[-- Type: text/plain, Size: 6417 bytes --]

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: Steven Rostedt <srostedt@redhat.com>
---
kernel/trace/ring_buffer.c | 65 +++++++++++++++++++++++++++++++++-----------
1 files changed, 49 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index ee9b93d..a6b8f9d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -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)) { \
@@ -201,10 +202,28 @@ struct ring_buffer_iter {
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); \
+ WARN_ON(1); \
return -1; \
} \
} 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;
}
@@ -1661,8 +1693,9 @@ 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) &&
- (iter->head + length > rb_commit_index(cpu_buffer)));
+ 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);

--
1.5.6.5

--