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| author | John Ogness <john.ogness@linutronix.de> | 2024-02-07 14:46:57 +0106 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2024-02-07 17:23:18 +0100 |
| commit | 584528d621459d1a5c31da7a591218ad3bb96d6c (patch) | |
| tree | f1a953e7b1024ff242d32f078f7c3af94919e24d /kernel/printk/printk_ringbuffer.c | |
| parent | 36652d0f3bf34899e82d31a5fa9e2bdd02fd6381 (diff) | |
| download | linux-584528d621459d1a5c31da7a591218ad3bb96d6c.tar.gz linux-584528d621459d1a5c31da7a591218ad3bb96d6c.tar.bz2 linux-584528d621459d1a5c31da7a591218ad3bb96d6c.zip | |
printk: ringbuffer: Cleanup reader terminology
With the lockless ringbuffer, it is allowed that multiple
CPUs/contexts write simultaneously into the buffer. This creates
an ambiguity as some writers will finalize sooner.
The documentation for the prb_read functions is not clear as it
refers to "not yet written" and "no data available". Clarify the
return values and language to be in terms of the reader: records
available for reading.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240207134103.1357162-9-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/printk/printk_ringbuffer.c')
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 244d991ffd73..67ee1c62fcd6 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -1987,11 +1987,13 @@ u64 prb_first_seq(struct printk_ringbuffer *rb) } /* - * Non-blocking read of a record. Updates @seq to the last finalized record - * (which may have no data available). + * Non-blocking read of a record. * - * See the description of prb_read_valid() and prb_read_valid_info() - * for details. + * On success @seq is updated to the record that was read and (if provided) + * @r and @line_count will contain the read/calculated data. + * + * On failure @seq is updated to a record that is not yet available to the + * reader, but it will be the next record available to the reader. */ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, struct printk_record *r, unsigned int *line_count) @@ -2010,7 +2012,7 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, *seq = tail_seq; } else if (err == -ENOENT) { - /* Record exists, but no data available. Skip. */ + /* Record exists, but the data was lost. Skip. */ (*seq)++; } else { @@ -2043,7 +2045,7 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, * On success, the reader must check r->info.seq to see which record was * actually read. This allows the reader to detect dropped records. * - * Failure means @seq refers to a not yet written record. + * Failure means @seq refers to a record not yet available to the reader. */ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, struct printk_record *r) @@ -2073,7 +2075,7 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, * On success, the reader must check info->seq to see which record meta data * was actually read. This allows the reader to detect dropped records. * - * Failure means @seq refers to a not yet written record. + * Failure means @seq refers to a record not yet available to the reader. */ bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq, struct printk_info *info, unsigned int *line_count) |