b24413180f560 (Greg Kroah-Hartman 2017-11-01 15:07:57 +0100 1) // SPDX-License-Identifier: GPL-2.0
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 2) #include <linux/err.h>
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 3) #include <linux/bug.h>
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 4) #include <linux/atomic.h>
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 5) #include <linux/errseq.h>
aa6159ab99a9a (Andy Shevchenko 2020-12-15 20:42:48 -0800 6) #include <linux/log2.h>
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 7)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 8) /*
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 9) * An errseq_t is a way of recording errors in one place, and allowing any
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 10) * number of "subscribers" to tell whether it has changed since a previous
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 11) * point where it was sampled.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 12) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 13) * It's implemented as an unsigned 32-bit value. The low order bits are
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 14) * designated to hold an error code (between 0 and -MAX_ERRNO). The upper bits
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 15) * are used as a counter. This is done with atomics instead of locking so that
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 16) * these functions can be called from any context.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 17) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 18) * The general idea is for consumers to sample an errseq_t value. That value
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 19) * can later be used to tell whether any new errors have occurred since that
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 20) * sampling was done.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 21) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 22) * Note that there is a risk of collisions if new errors are being recorded
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 23) * frequently, since we have so few bits to use as a counter.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 24) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 25) * To mitigate this, one bit is used as a flag to tell whether the value has
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 26) * been sampled since a new value was recorded. That allows us to avoid bumping
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 27) * the counter if no one has sampled it since the last time an error was
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 28) * recorded.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 29) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 30) * A new errseq_t should always be zeroed out. A errseq_t value of all zeroes
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 31) * is the special (but common) case where there has never been an error. An all
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 32) * zero value thus serves as the "epoch" if one wishes to know whether there
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 33) * has ever been an error set since it was first initialized.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 34) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 35)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 36) /* The low bits are designated for error code (max of MAX_ERRNO) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 37) #define ERRSEQ_SHIFT ilog2(MAX_ERRNO + 1)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 38)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 39) /* This bit is used as a flag to indicate whether the value has been seen */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 40) #define ERRSEQ_SEEN (1 << ERRSEQ_SHIFT)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 41)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 42) /* The lowest bit of the counter */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 43) #define ERRSEQ_CTR_INC (1 << (ERRSEQ_SHIFT + 1))
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 44)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 45) /**
3acdfd280fe7d (Jeff Layton 2017-07-24 06:22:15 -0400 46) * errseq_set - set a errseq_t for later reporting
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 47) * @eseq: errseq_t field that should be set
3acdfd280fe7d (Jeff Layton 2017-07-24 06:22:15 -0400 48) * @err: error to set (must be between -1 and -MAX_ERRNO)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 49) *
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 50) * This function sets the error in @eseq, and increments the sequence counter
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 51) * if the last sequence was sampled at some point in the past.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 52) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 53) * Any error set will always overwrite an existing error.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 54) *
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 55) * Return: The previous value, primarily for debugging purposes. The
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 56) * return value should not be used as a previously sampled value in later
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 57) * calls as it will not have the SEEN flag set.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 58) */
3acdfd280fe7d (Jeff Layton 2017-07-24 06:22:15 -0400 59) errseq_t errseq_set(errseq_t *eseq, int err)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 60) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 61) errseq_t cur, old;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 62)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 63) /* MAX_ERRNO must be able to serve as a mask */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 64) BUILD_BUG_ON_NOT_POWER_OF_2(MAX_ERRNO + 1);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 65)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 66) /*
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 67) * Ensure the error code actually fits where we want it to go. If it
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 68) * doesn't then just throw a warning and don't record anything. We
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 69) * also don't accept zero here as that would effectively clear a
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 70) * previous error.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 71) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 72) old = READ_ONCE(*eseq);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 73)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 74) if (WARN(unlikely(err == 0 || (unsigned int)-err > MAX_ERRNO),
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 75) "err = %d\n", err))
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 76) return old;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 77)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 78) for (;;) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 79) errseq_t new;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 80)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 81) /* Clear out error bits and set new error */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 82) new = (old & ~(MAX_ERRNO|ERRSEQ_SEEN)) | -err;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 83)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 84) /* Only increment if someone has looked at it */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 85) if (old & ERRSEQ_SEEN)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 86) new += ERRSEQ_CTR_INC;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 87)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 88) /* If there would be no change, then call it done */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 89) if (new == old) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 90) cur = new;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 91) break;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 92) }
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 93)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 94) /* Try to swap the new value into place */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 95) cur = cmpxchg(eseq, old, new);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 96)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 97) /*
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 98) * Call it success if we did the swap or someone else beat us
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 99) * to it for the same value.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 100) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 101) if (likely(cur == old || cur == new))
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 102) break;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 103)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 104) /* Raced with an update, try again */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 105) old = cur;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 106) }
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 107) return cur;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 108) }
3acdfd280fe7d (Jeff Layton 2017-07-24 06:22:15 -0400 109) EXPORT_SYMBOL(errseq_set);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 110)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 111) /**
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 112) * errseq_sample() - Grab current errseq_t value.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 113) * @eseq: Pointer to errseq_t to be sampled.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 114) *
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 115) * This function allows callers to initialise their errseq_t variable.
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 116) * If the error has been "seen", new callers will not see an old error.
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 117) * If there is an unseen error in @eseq, the caller of this function will
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 118) * see it the next time it checks for an error.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 119) *
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 120) * Context: Any context.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 121) * Return: The current errseq value.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 122) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 123) errseq_t errseq_sample(errseq_t *eseq)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 124) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 125) errseq_t old = READ_ONCE(*eseq);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 126)
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 127) /* If nobody has seen this error yet, then we can be the first. */
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 128) if (!(old & ERRSEQ_SEEN))
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 129) old = 0;
b4678df184b31 (Matthew Wilcox 2018-04-24 14:02:57 -0700 130) return old;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 131) }
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 132) EXPORT_SYMBOL(errseq_sample);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 133)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 134) /**
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 135) * errseq_check() - Has an error occurred since a particular sample point?
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 136) * @eseq: Pointer to errseq_t value to be checked.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 137) * @since: Previously-sampled errseq_t from which to check.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 138) *
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 139) * Grab the value that eseq points to, and see if it has changed @since
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 140) * the given value was sampled. The @since value is not advanced, so there
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 141) * is no need to mark the value as seen.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 142) *
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 143) * Return: The latest error set in the errseq_t or 0 if it hasn't changed.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 144) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 145) int errseq_check(errseq_t *eseq, errseq_t since)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 146) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 147) errseq_t cur = READ_ONCE(*eseq);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 148)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 149) if (likely(cur == since))
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 150) return 0;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 151) return -(cur & MAX_ERRNO);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 152) }
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 153) EXPORT_SYMBOL(errseq_check);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 154)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 155) /**
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 156) * errseq_check_and_advance() - Check an errseq_t and advance to current value.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 157) * @eseq: Pointer to value being checked and reported.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 158) * @since: Pointer to previously-sampled errseq_t to check against and advance.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 159) *
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 160) * Grab the eseq value, and see whether it matches the value that @since
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 161) * points to. If it does, then just return 0.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 162) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 163) * If it doesn't, then the value has changed. Set the "seen" flag, and try to
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 164) * swap it into place as the new eseq value. Then, set that value as the new
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 165) * "since" value, and return whatever the error portion is set to.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 166) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 167) * Note that no locking is provided here for concurrent updates to the "since"
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 168) * value. The caller must provide that if necessary. Because of this, callers
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 169) * may want to do a lockless errseq_check before taking the lock and calling
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 170) * this.
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 171) *
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 172) * Return: Negative errno if one has been stored, or 0 if no new error has
14ebc28e07e68 (Matthew Wilcox 2017-12-22 06:32:16 -0800 173) * occurred.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 174) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 175) int errseq_check_and_advance(errseq_t *eseq, errseq_t *since)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 176) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 177) int err = 0;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 178) errseq_t old, new;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 179)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 180) /*
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 181) * Most callers will want to use the inline wrapper to check this,
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 182) * so that the common case of no error is handled without needing
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 183) * to take the lock that protects the "since" value.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 184) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 185) old = READ_ONCE(*eseq);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 186) if (old != *since) {
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 187) /*
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 188) * Set the flag and try to swap it into place if it has
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 189) * changed.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 190) *
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 191) * We don't care about the outcome of the swap here. If the
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 192) * swap doesn't occur, then it has either been updated by a
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 193) * writer who is altering the value in some way (updating
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 194) * counter or resetting the error), or another reader who is
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 195) * just setting the "seen" flag. Either outcome is OK, and we
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 196) * can advance "since" and return an error based on what we
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 197) * have.
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 198) */
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 199) new = old | ERRSEQ_SEEN;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 200) if (new != old)
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 201) cmpxchg(eseq, old, new);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 202) *since = new;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 203) err = -(new & MAX_ERRNO);
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 204) }
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 205) return err;
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 206) }
84cbadadc6eaf (Jeff Layton 2017-07-06 07:02:24 -0400 207) EXPORT_SYMBOL(errseq_check_and_advance);
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