67 lines
2.8 KiB
Diff
67 lines
2.8 KiB
Diff
From: John Ogness <john.ogness@linutronix.de>
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Date: Mon, 6 Nov 2023 15:01:58 +0000
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Subject: [PATCH 092/134] printk: ringbuffer: Cleanup reader terminology
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz
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With the lockless ringbuffer, it is allowed that multiple
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CPUs/contexts write simultaneously into the buffer. This creates
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an ambiguity as some writers will finalize sooner.
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The documentation for the prb_read functions is not clear as it
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refers to "not yet written" and "no data available". Clarify the
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return values and language to be in terms of the reader: records
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available for reading.
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Signed-off-by: John Ogness <john.ogness@linutronix.de>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/printk/printk_ringbuffer.c | 16 +++++++++-------
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1 file changed, 9 insertions(+), 7 deletions(-)
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--- a/kernel/printk/printk_ringbuffer.c
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+++ b/kernel/printk/printk_ringbuffer.c
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@@ -1987,11 +1987,13 @@ u64 prb_first_seq(struct printk_ringbuff
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}
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/*
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- * Non-blocking read of a record. Updates @seq to the last finalized record
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- * (which may have no data available).
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+ * Non-blocking read of a record.
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*
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- * See the description of prb_read_valid() and prb_read_valid_info()
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- * for details.
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+ * On success @seq is updated to the record that was read and (if provided)
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+ * @r and @line_count will contain the read/calculated data.
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+ *
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+ * On failure @seq is updated to a record that is not yet available to the
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+ * reader, but it will be the next record available to the reader.
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*/
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static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq,
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struct printk_record *r, unsigned int *line_count)
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@@ -2010,7 +2012,7 @@ static bool _prb_read_valid(struct print
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*seq = tail_seq;
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} else if (err == -ENOENT) {
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- /* Record exists, but no data available. Skip. */
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+ /* Record exists, but the data was lost. Skip. */
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(*seq)++;
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} else {
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@@ -2043,7 +2045,7 @@ static bool _prb_read_valid(struct print
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* On success, the reader must check r->info.seq to see which record was
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* actually read. This allows the reader to detect dropped records.
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*
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- * Failure means @seq refers to a not yet written record.
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+ * Failure means @seq refers to a record not yet available to the reader.
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*/
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bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq,
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struct printk_record *r)
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@@ -2073,7 +2075,7 @@ bool prb_read_valid(struct printk_ringbu
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* On success, the reader must check info->seq to see which record meta data
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* was actually read. This allows the reader to detect dropped records.
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*
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- * Failure means @seq refers to a not yet written record.
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+ * Failure means @seq refers to a record not yet available to the reader.
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*/
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bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq,
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struct printk_info *info, unsigned int *line_count)
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