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| author | Matthew Wilcox <mawilcox@microsoft.com> | 2017-12-22 06:32:16 -0800 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2018-01-01 12:40:27 -0700 |
| commit | 14ebc28e07e68ff412aa42f7d8b67969e2f63d00 (patch) | |
| tree | 7d5aa02eba4a70f4d8da61e51eae16e0c7956567 /Documentation | |
| parent | aa931b44ae3e32329b054e3cd8ba1a4f1aa9e0d8 (diff) | |
| download | linux-14ebc28e07e68ff412aa42f7d8b67969e2f63d00.tar.gz linux-14ebc28e07e68ff412aa42f7d8b67969e2f63d00.tar.bz2 linux-14ebc28e07e68ff412aa42f7d8b67969e2f63d00.zip | |
errseq: Add to documentation tree
- Move errseq.rst into core-api
- Add errseq to the core-api index
- Promote the header to a more prominent header type, otherwise we get three
entries in the table of contents.
- Reformat the table to look nicer and be a little more proportional in
terms of horizontal width per bit (the SF bit is still disproportionately
large, but there's no way to fix that).
- Include errseq kernel-doc in the errseq.rst
- Neaten some kernel-doc markup
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/core-api/errseq.rst (renamed from Documentation/errseq.rst) | 20 | ||||
| -rw-r--r-- | Documentation/core-api/index.rst | 1 |
2 files changed, 16 insertions, 5 deletions
diff --git a/Documentation/errseq.rst b/Documentation/core-api/errseq.rst index 4c29bd5afbc5..ff332e272405 100644 --- a/Documentation/errseq.rst +++ b/Documentation/core-api/errseq.rst @@ -1,5 +1,7 @@ +===================== The errseq_t datatype ===================== + An errseq_t is a way of recording errors in one place, and allowing any number of "subscribers" to tell whether it has changed since a previous point where it was sampled. @@ -21,12 +23,13 @@ a flag to tell whether the value has been sampled since a new value was recorded. That allows us to avoid bumping the counter if no one has sampled it since the last time an error was recorded. -Thus we end up with a value that looks something like this:: +Thus we end up with a value that looks something like this: - bit: 31..13 12 11..0 - +-----------------+----+----------------+ - | counter | SF | errno | - +-----------------+----+----------------+ ++--------------------------------------+----+------------------------+ +| 31..13 | 12 | 11..0 | ++--------------------------------------+----+------------------------+ +| counter | SF | errno | ++--------------------------------------+----+------------------------+ The general idea is for "watchers" to sample an errseq_t value and keep it as a running cursor. That value can later be used to tell whether @@ -42,6 +45,7 @@ has ever been an error set since it was first initialized. API usage ========= + Let me tell you a story about a worker drone. Now, he's a good worker overall, but the company is a little...management heavy. He has to report to 77 supervisors today, and tomorrow the "big boss" is coming in @@ -125,6 +129,7 @@ not usable by anyone else. Serializing errseq_t cursor updates =================================== + Note that the errseq_t API does not protect the errseq_t cursor during a check_and_advance_operation. Only the canonical error code is handled atomically. In a situation where more than one task might be using the @@ -147,3 +152,8 @@ errseq_check_and_advance after taking the lock. e.g.:: That avoids the spinlock in the common case where nothing has changed since the last time it was checked. + +Functions +========= + +.. kernel-doc:: lib/errseq.c diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index d55ee6b006ed..1b1fd01990b5 100644 --- a/Documentation/core-api/index.rst +++ b/Documentation/core-api/index.rst @@ -22,6 +22,7 @@ Core utilities flexible-arrays librs genalloc + errseq printk-formats Interfaces for kernel debugging |