diff options
| author | Wang Wensheng <wsw9603@163.com> | 2026-09-26 17:45:02 +0800 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2026-09-29 16:50:37 +0200 |
| commit | 267f1127c0f4035448acc6f2c3321eb38e54eecc (patch) | |
| tree | b9c5bd97be671151e126247140b01709eb414f7f /kernel | |
| parent | 731383dcf511c4d9ee00b3dc9f4f65689e233401 (diff) | |
| download | linux-267f1127c0f4035448acc6f2c3321eb38e54eecc.tar.gz linux-267f1127c0f4035448acc6f2c3321eb38e54eecc.zip | |
printk_ringbuffer: Avoid needless read of prb_desc
Since commit f244b4dc53e5 ("printk: ringbuffer: Improve prb_next_seq()
performance"), desc_read() allows @desc_out to be NULL. We can drop the
local `desc` variable in desc_reopen_last() and prb_first_seq(). Also
update the comment for desc_read().
v1->v2:
Update the comment suggested by John.
Signed-off-by: Wang Wensheng <wsw9603@163.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://patch.msgid.link/20260926094502.251204-1-wsw9603@163.com
Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 85c0c854b3ce..d38e7c2f6887 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -439,13 +439,12 @@ static enum desc_state get_desc_state(unsigned long id, } /* - * Get a copy of a specified descriptor and return its queried state. If the - * descriptor is in an inconsistent state (miss or reserved), the caller can - * only expect the descriptor's @state_var field to be valid. + * Get the state of a specified descriptor. * - * The sequence number and caller_id can be optionally retrieved. Like all - * non-state_var data, they are only valid if the descriptor is in a - * consistent state. + * Optionally, a copy of the descriptor, sequence number and/or caller ID can + * be retrieved. However, (with the exception of @desc_out->state_var) all + * retrieved values are invalid if the descriptor is in an inconsistent state + * (miss or reserved). */ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, unsigned long id, struct prb_desc *desc_out, @@ -1335,7 +1334,6 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring, { unsigned long prev_state_val; enum desc_state d_state; - struct prb_desc desc; struct prb_desc *d; unsigned long id; u32 cid; @@ -1346,7 +1344,7 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring, * To reduce unnecessarily reopening, first check if the descriptor * state and caller ID are correct. */ - d_state = desc_read(desc_ring, id, &desc, NULL, &cid); + d_state = desc_read(desc_ring, id, NULL, NULL, &cid); if (d_state != desc_committed || cid != caller_id) return NULL; @@ -2007,14 +2005,13 @@ u64 prb_first_seq(struct printk_ringbuffer *rb) { struct prb_desc_ring *desc_ring = &rb->desc_ring; enum desc_state d_state; - struct prb_desc desc; unsigned long id; u64 seq; for (;;) { id = atomic_long_read(&rb->desc_ring.tail_id); /* LMM(prb_first_seq:A) */ - d_state = desc_read(desc_ring, id, &desc, &seq, NULL); /* LMM(prb_first_seq:B) */ + d_state = desc_read(desc_ring, id, NULL, &seq, NULL); /* LMM(prb_first_seq:B) */ /* * This loop will not be infinite because the tail is |