@@ -5036,13 +5036,9 @@ EXPORT_SYMBOL_GPL(ring_buffer_consume);
* @flags: gfp flags to use for memory allocation
*
* This performs the initial preparations necessary to iterate
- * through the buffer. Memory is allocated, buffer recording
+ * through the buffer. Memory is allocated, buffer resizing
* is disabled, and the iterator pointer is returned to the caller.
*
- * Disabling buffer recording prevents the reading from being
- * corrupted. This is not a consuming read, so a producer is not
- * expected.
- *
* After a sequence of ring_buffer_read_prepare calls, the user is
* expected to make at least one call to ring_buffer_read_prepare_sync.
* Afterwards, ring_buffer_read_start is invoked to get things going
@@ -5129,8 +5125,7 @@ EXPORT_SYMBOL_GPL(ring_buffer_read_start);
* ring_buffer_read_finish - finish reading the iterator of the buffer
* @iter: The iterator retrieved by ring_buffer_start
*
- * This re-enables the recording to the buffer, and frees the
- * iterator.
+ * This re-enables resizing of the buffer, and frees the iterator.
*/
void
ring_buffer_read_finish(struct ring_buffer_iter *iter)
@@ -5138,12 +5133,7 @@ ring_buffer_read_finish(struct ring_buffer_iter *iter)
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
unsigned long flags;
- /*
- * Ring buffer is disabled from recording, here's a good place
- * to check the integrity of the ring buffer.
- * Must prevent readers from trying to read, as the check
- * clears the HEAD page and readers require it.
- */
+ /* Use this opportunity to check the integrity of the ring buffer. */
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_check_pages(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
Adjust the following code documentation: * Kernel-doc comments for ring_buffer_read_prepare() and ring_buffer_read_finish() mention that recording to the ring buffer is disabled when the read is active. Remove mention of this restriction because it was already lifted in commit 1039221cc278 ("ring-buffer: Do not disable recording when there is an iterator"). * Function ring_buffer_read_finish() performs a self-check of the ring-buffer by locking cpu_buffer->reader_lock and then calling rb_check_pages(). The preceding comment explains that the lock is needed because rb_check_pages() clears the HEAD flag required by readers which might be running in parallel. Remove this explanation because commit 8843e06f67b1 ("ring-buffer: Handle race between rb_move_tail and rb_check_pages") simplified the function so it no longer resets the mentioned flag. Nonetheless, the lock is still needed because a reader swapping a page into the ring buffer can make the underlying doubly-linked list temporarily inconsistent. This is a non-functional change. Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> --- kernel/trace/ring_buffer.c | 16 +++------------- 1 file changed, 3 insertions(+), 13 deletions(-)