diff options
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 |