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>hifive-unleashed-5.1
Matthew Wilcox
Jonathan Corbet
parent
aa931b44ae
commit
14ebc28e07
|
|
@ -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
|
||||
|
|
@ -22,6 +22,7 @@ Core utilities
|
|||
flexible-arrays
|
||||
librs
|
||||
genalloc
|
||||
errseq
|
||||
printk-formats
|
||||
|
||||
Interfaces for kernel debugging
|
||||
|
|
|
|||
|
|
@ -1,6 +1,6 @@
|
|||
/* SPDX-License-Identifier: GPL-2.0 */
|
||||
/*
|
||||
* See Documentation/errseq.rst and lib/errseq.c
|
||||
* See Documentation/core-api/errseq.rst and lib/errseq.c
|
||||
*/
|
||||
#ifndef _LINUX_ERRSEQ_H
|
||||
#define _LINUX_ERRSEQ_H
|
||||
|
|
|
|||
37
lib/errseq.c
37
lib/errseq.c
|
|
@ -46,14 +46,14 @@
|
|||
* @eseq: errseq_t field that should be set
|
||||
* @err: error to set (must be between -1 and -MAX_ERRNO)
|
||||
*
|
||||
* This function sets the error in *eseq, and increments the sequence counter
|
||||
* This function sets the error in @eseq, and increments the sequence counter
|
||||
* if the last sequence was sampled at some point in the past.
|
||||
*
|
||||
* Any error set will always overwrite an existing error.
|
||||
*
|
||||
* We do return the latest value here, primarily for debugging purposes. The
|
||||
* return value should not be used as a previously sampled value in later calls
|
||||
* as it will not have the SEEN flag set.
|
||||
* Return: The previous value, primarily for debugging purposes. The
|
||||
* return value should not be used as a previously sampled value in later
|
||||
* calls as it will not have the SEEN flag set.
|
||||
*/
|
||||
errseq_t errseq_set(errseq_t *eseq, int err)
|
||||
{
|
||||
|
|
@ -108,11 +108,13 @@ errseq_t errseq_set(errseq_t *eseq, int err)
|
|||
EXPORT_SYMBOL(errseq_set);
|
||||
|
||||
/**
|
||||
* errseq_sample - grab current errseq_t value
|
||||
* @eseq: pointer to errseq_t to be sampled
|
||||
* errseq_sample() - Grab current errseq_t value.
|
||||
* @eseq: Pointer to errseq_t to be sampled.
|
||||
*
|
||||
* This function allows callers to sample an errseq_t value, marking it as
|
||||
* "seen" if required.
|
||||
*
|
||||
* Return: The current errseq value.
|
||||
*/
|
||||
errseq_t errseq_sample(errseq_t *eseq)
|
||||
{
|
||||
|
|
@ -134,15 +136,15 @@ errseq_t errseq_sample(errseq_t *eseq)
|
|||
EXPORT_SYMBOL(errseq_sample);
|
||||
|
||||
/**
|
||||
* errseq_check - has an error occurred since a particular sample point?
|
||||
* @eseq: pointer to errseq_t value to be checked
|
||||
* @since: previously-sampled errseq_t from which to check
|
||||
* errseq_check() - Has an error occurred since a particular sample point?
|
||||
* @eseq: Pointer to errseq_t value to be checked.
|
||||
* @since: Previously-sampled errseq_t from which to check.
|
||||
*
|
||||
* Grab the value that eseq points to, and see if it has changed "since"
|
||||
* the given value was sampled. The "since" value is not advanced, so there
|
||||
* Grab the value that eseq points to, and see if it has changed @since
|
||||
* the given value was sampled. The @since value is not advanced, so there
|
||||
* is no need to mark the value as seen.
|
||||
*
|
||||
* Returns the latest error set in the errseq_t or 0 if it hasn't changed.
|
||||
* Return: The latest error set in the errseq_t or 0 if it hasn't changed.
|
||||
*/
|
||||
int errseq_check(errseq_t *eseq, errseq_t since)
|
||||
{
|
||||
|
|
@ -155,11 +157,11 @@ int errseq_check(errseq_t *eseq, errseq_t since)
|
|||
EXPORT_SYMBOL(errseq_check);
|
||||
|
||||
/**
|
||||
* errseq_check_and_advance - check an errseq_t and advance to current value
|
||||
* @eseq: pointer to value being checked and reported
|
||||
* @since: pointer to previously-sampled errseq_t to check against and advance
|
||||
* errseq_check_and_advance() - Check an errseq_t and advance to current value.
|
||||
* @eseq: Pointer to value being checked and reported.
|
||||
* @since: Pointer to previously-sampled errseq_t to check against and advance.
|
||||
*
|
||||
* Grab the eseq value, and see whether it matches the value that "since"
|
||||
* Grab the eseq value, and see whether it matches the value that @since
|
||||
* points to. If it does, then just return 0.
|
||||
*
|
||||
* If it doesn't, then the value has changed. Set the "seen" flag, and try to
|
||||
|
|
@ -170,6 +172,9 @@ EXPORT_SYMBOL(errseq_check);
|
|||
* value. The caller must provide that if necessary. Because of this, callers
|
||||
* may want to do a lockless errseq_check before taking the lock and calling
|
||||
* this.
|
||||
*
|
||||
* Return: Negative errno if one has been stored, or 0 if no new error has
|
||||
* occurred.
|
||||
*/
|
||||
int errseq_check_and_advance(errseq_t *eseq, errseq_t *since)
|
||||
{
|
||||
|
|
|
|||
Loading…
Reference in New Issue