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Diffstat (limited to 'Documentation/locking/seqlock.rst')
| -rw-r--r-- | Documentation/locking/seqlock.rst | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/Documentation/locking/seqlock.rst b/Documentation/locking/seqlock.rst index bfda1a5fecad..9899871d3d9a 100644 --- a/Documentation/locking/seqlock.rst +++ b/Documentation/locking/seqlock.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + ====================================== Sequence counters and sequential locks ====================================== @@ -153,7 +155,7 @@ Use seqcount_latch_t when the write side sections cannot be protected from interruption by readers. This is typically the case when the read side can be invoked from NMI handlers. -Check `raw_write_seqcount_latch()` for more information. +Check `write_seqcount_latch()` for more information. .. _seqlock_t: @@ -218,13 +220,14 @@ Read path, three categories: according to a passed marker. This is used to avoid lockless readers starvation (too much retry loops) in case of a sharp spike in write activity. First, a lockless read is tried (even marker passed). If - that trial fails (odd sequence counter is returned, which is used as - the next iteration marker), the lockless read is transformed to a - full locking read and no retry loop is necessary:: + that trial fails (sequence counter doesn't match), make the marker + odd for the next iteration, the lockless read is transformed to a + full locking read and no retry loop is necessary, for example:: /* marker; even initialization */ - int seq = 0; + int seq = 1; do { + seq++; /* 2 on the 1st/lockless path, otherwise odd */ read_seqbegin_or_lock(&foo_seqlock, &seq); /* ... [[read-side critical section]] ... */ |