Commit bf56987c authored by Loïc Grégoire's avatar Loïc Grégoire Committed by Petr Mladek
Browse files

printk: ringbuffer: fix errors in comments 



The printk ringbuffer implementation is described in the comment as
using three ringbuffers, but the current implementation uses two (desc
and data). Update the comment so it matches the code.

Fix few more known issues in the comments.

Signed-off-by: default avatarLoïc Grégoire <loicgre@gmail.com>
Reviewed-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20260328021855.53956-1-loicgre@gmail.com


[pmladek@suse.com: Fixed few more issues in the comments by John Ogness.]
Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent 407f666d

kernel/printk/printk_ringbuffer.c

+6 −6
Original line number Diff line number Diff line
@@ -14,7 +14,7 @@ 
 *

 * Data Structure

 * --------------

 * The printk_ringbuffer is made up of 3 internal ringbuffers:

 * The printk_ringbuffer is made up of 2 internal ringbuffers:

 *

 *   desc_ring

 *     A ring of descriptors and their meta data (such as sequence number,
@@ -224,7 +224,7 @@ 
 *

 *	prb_rec_init_rd(&r, &info, &text_buf[0], sizeof(text_buf));

 *

 *	prb_for_each_record(0, &test_rb, &seq, &r) {

 *	prb_for_each_record(0, &test_rb, seq, &r) {

 *		if (info.seq != seq)

 *			pr_warn("lost %llu records\n", info.seq - seq);

 *
@@ -1368,7 +1368,7 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring, 
	 *

	 * WMB from _prb_commit:A to _prb_commit:B

	 *    matching

	 * MB If desc_reopen_last:A to prb_reserve_in_last:A

	 * MB from desc_reopen_last:A to prb_reserve_in_last:A

	 */

	if (!atomic_long_try_cmpxchg(&d->state_var, &prev_state_val,

			DESC_SV(id, desc_reserved))) { /* LMM(desc_reopen_last:A) */
@@ -1773,9 +1773,9 @@ static void _prb_commit(struct prb_reserved_entry *e, unsigned long state_val) 
	 *

	 *    Relies on:

	 *

	 *    MB _prb_commit:B to prb_commit:A

	 *    MB from _prb_commit:B to prb_commit:A

	 *       matching

	 *    MB desc_reserve:D to desc_make_final:A

	 *    MB from desc_reserve:D to desc_make_final:A

	 */

	if (!atomic_long_try_cmpxchg(&d->state_var, &prev_state_val,

			DESC_SV(e->id, state_val))) { /* LMM(_prb_commit:B) */
@@ -2038,7 +2038,7 @@ u64 prb_first_seq(struct printk_ringbuffer *rb) 
		 *

		 * MB from desc_push_tail:B to desc_reserve:F

		 *    matching

		 * RMB prb_first_seq:B to prb_first_seq:A

		 * RMB from prb_first_seq:B to prb_first_seq:A

		 */

		smp_rmb(); /* LMM(prb_first_seq:C) */

	}

kernel/printk/printk_ringbuffer.h

+1 −1
Original line number Diff line number Diff line
@@ -383,7 +383,7 @@ for ((s) = from; prb_read_valid(rb, s, r); (s) = (r)->info->seq + 1) 
 *

 * This is a macro for conveniently iterating over a ringbuffer.

 * Note that @s may not be the sequence number of the record on each

 * iteration. For the sequence number, @r->info->seq should be checked.

 * iteration. For the sequence number, @i->seq should be checked.

 *

 * Context: Any context.

 */