diff options
Diffstat (limited to 'lib/errseq.c')
| -rw-r--r-- | lib/errseq.c | 86 |
1 files changed, 43 insertions, 43 deletions
diff --git a/lib/errseq.c b/lib/errseq.c index 841fa24e6e00..13a2581c5a87 100644 --- a/lib/errseq.c +++ b/lib/errseq.c @@ -1,7 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 #include <linux/err.h> #include <linux/bug.h> #include <linux/atomic.h> #include <linux/errseq.h> +#include <linux/log2.h> /* * An errseq_t is a way of recording errors in one place, and allowing any @@ -32,37 +34,35 @@ */ /* The low bits are designated for error code (max of MAX_ERRNO) */ -#define ERRSEQ_SHIFT ilog2(MAX_ERRNO + 1) +#define ERRSEQ_SHIFT (ilog2(MAX_ERRNO) + 1) /* This bit is used as a flag to indicate whether the value has been seen */ #define ERRSEQ_SEEN (1 << ERRSEQ_SHIFT) +/* Leverage macro ERRSEQ_SEEN to define errno mask macro here */ +#define ERRNO_MASK (ERRSEQ_SEEN - 1) + /* The lowest bit of the counter */ #define ERRSEQ_CTR_INC (1 << (ERRSEQ_SHIFT + 1)) /** - * __errseq_set - set a errseq_t for later reporting + * errseq_set - set a errseq_t for later reporting * @eseq: errseq_t field that should be set - * @err: error to 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. * - * Most callers will want to use the errseq_set inline wrapper to efficiently - * handle the common case where err is 0. - * - * We do return an errseq_t 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) +errseq_t errseq_set(errseq_t *eseq, int err) { errseq_t cur, old; - /* MAX_ERRNO must be able to serve as a mask */ - BUILD_BUG_ON_NOT_POWER_OF_2(MAX_ERRNO + 1); /* * Ensure the error code actually fits where we want it to go. If it @@ -80,7 +80,7 @@ errseq_t __errseq_set(errseq_t *eseq, int err) errseq_t new; /* Clear out error bits and set new error */ - new = (old & ~(MAX_ERRNO|ERRSEQ_SEEN)) | -err; + new = (old & ~(ERRNO_MASK | ERRSEQ_SEEN)) | -err; /* Only increment if someone has looked at it */ if (old & ERRSEQ_SEEN) @@ -107,44 +107,41 @@ errseq_t __errseq_set(errseq_t *eseq, int err) } return cur; } -EXPORT_SYMBOL(__errseq_set); +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. + * This function allows callers to initialise their errseq_t variable. + * If the error has been "seen", new callers will not see an old error. + * If there is an unseen error in @eseq, the caller of this function will + * see it the next time it checks for an error. + * + * Context: Any context. + * Return: The current errseq value. */ errseq_t errseq_sample(errseq_t *eseq) { errseq_t old = READ_ONCE(*eseq); - errseq_t new = old; - /* - * For the common case of no errors ever having been set, we can skip - * marking the SEEN bit. Once an error has been set, the value will - * never go back to zero. - */ - if (old != 0) { - new |= ERRSEQ_SEEN; - if (old != new) - cmpxchg(eseq, old, new); - } - return new; + /* If nobody has seen this error yet, then we can be the first. */ + if (!(old & ERRSEQ_SEEN)) + old = 0; + return old; } 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) { @@ -152,16 +149,16 @@ int errseq_check(errseq_t *eseq, errseq_t since) if (likely(cur == since)) return 0; - return -(cur & MAX_ERRNO); + return -(cur & ERRNO_MASK); } 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 @@ -172,6 +169,9 @@ 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) { @@ -201,7 +201,7 @@ int errseq_check_and_advance(errseq_t *eseq, errseq_t *since) if (new != old) cmpxchg(eseq, old, new); *since = new; - err = -(new & MAX_ERRNO); + err = -(new & ERRNO_MASK); } return err; } |