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tor/src/ext/timeouts/timeout.c

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/* ==========================================================================
* timeout.c - Tickless hierarchical timing wheel.
* --------------------------------------------------------------------------
* Copyright (c) 2013, 2014 William Ahern
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to permit
* persons to whom the Software is furnished to do so, subject to the
* following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
* NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
* ==========================================================================
*/
#ifdef HAVE_CONFIG_H
#include "orconfig.h"
#endif
#include <limits.h> /* CHAR_BIT */
#include <stddef.h> /* NULL */
#include <stdlib.h> /* malloc(3) free(3) */
#include <stdio.h> /* FILE fprintf(3) */
#include <inttypes.h> /* UINT64_C uint64_t */
#include <string.h> /* memset(3) */
#include <errno.h> /* errno */
#include <sys/queue.h> /* TAILQ(3) */
#include "timeout.h"
#ifndef TIMEOUT_DEBUG
#define TIMEOUT_DEBUG 0
#endif
#if TIMEOUT_DEBUG - 0
#include "timeout-debug.h"
#endif
#ifdef TIMEOUT_DISABLE_RELATIVE_ACCESS
#define TO_SET_TIMEOUTS(to, T) ((void)0)
#else
#define TO_SET_TIMEOUTS(to, T) ((to)->timeouts = (T))
#endif
/*
* A N C I L L A R Y R O U T I N E S
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#define abstime_t timeout_t /* for documentation purposes */
#define reltime_t timeout_t /* "" */
#if !defined countof
#define countof(a) (sizeof (a) / sizeof *(a))
#endif
#if !defined endof
#define endof(a) (&(a)[countof(a)])
#endif
#if !defined MIN
#define MIN(a, b) (((a) < (b))? (a) : (b))
#endif
#if !defined MAX
#define MAX(a, b) (((a) > (b))? (a) : (b))
#endif
#if !defined TAILQ_CONCAT
#define TAILQ_CONCAT(head1, head2, field) do { \
if (!TAILQ_EMPTY(head2)) { \
*(head1)->tqh_last = (head2)->tqh_first; \
(head2)->tqh_first->field.tqe_prev = (head1)->tqh_last; \
(head1)->tqh_last = (head2)->tqh_last; \
TAILQ_INIT((head2)); \
} \
} while (0)
#endif
#if !defined TAILQ_FOREACH_SAFE
#define TAILQ_FOREACH_SAFE(var, head, field, tvar) \
for ((var) = TAILQ_FIRST(head); \
(var) && ((tvar) = TAILQ_NEXT(var, field), 1); \
(var) = (tvar))
#endif
/*
* B I T M A N I P U L A T I O N R O U T I N E S
*
* The macros and routines below implement wheel parameterization. The
* inputs are:
*
* WHEEL_BIT - The number of value bits mapped in each wheel. The
* lowest-order WHEEL_BIT bits index the lowest-order (highest
* resolution) wheel, the next group of WHEEL_BIT bits the
* higher wheel, etc.
*
* WHEEL_NUM - The number of wheels. WHEEL_BIT * WHEEL_NUM = the number of
* value bits used by all the wheels. For the default of 6 and
* 4, only the low 24 bits are processed. Any timeout value
* larger than this will cycle through again.
*
* The implementation uses bit fields to remember which slot in each wheel
* is populated, and to generate masks of expiring slots according to the
* current update interval (i.e. the "tickless" aspect). The slots to
* process in a wheel are (populated-set & interval-mask).
*
* WHEEL_BIT cannot be larger than 6 bits because 2^6 -> 64 is the largest
* number of slots which can be tracked in a uint64_t integer bit field.
* WHEEL_BIT cannot be smaller than 3 bits because of our rotr and rotl
* routines, which only operate on all the value bits in an integer, and
* there's no integer smaller than uint8_t.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#if !defined WHEEL_BIT
#define WHEEL_BIT 6
#endif
#if !defined WHEEL_NUM
#define WHEEL_NUM 4
#endif
#define WHEEL_LEN (1U << WHEEL_BIT)
#define WHEEL_MAX (WHEEL_LEN - 1)
#define WHEEL_MASK (WHEEL_LEN - 1)
#define TIMEOUT_MAX ((TIMEOUT_C(1) << (WHEEL_BIT * WHEEL_NUM)) - 1)
#include "timeout-bitops.c"
#if WHEEL_BIT == 6
#define ctz(n) ctz64(n)
#define clz(n) clz64(n)
#define fls(n) ((int)(64 - clz64(n)))
#else
#define ctz(n) ctz32(n)
#define clz(n) clz32(n)
#define fls(n) ((int)(32 - clz32(n)))
#endif
#if WHEEL_BIT == 6
#define WHEEL_C(n) UINT64_C(n)
#define WHEEL_PRIu PRIu64
#define WHEEL_PRIx PRIx64
typedef uint64_t wheel_t;
#elif WHEEL_BIT == 5
#define WHEEL_C(n) UINT32_C(n)
#define WHEEL_PRIu PRIu32
#define WHEEL_PRIx PRIx32
typedef uint32_t wheel_t;
#elif WHEEL_BIT == 4
#define WHEEL_C(n) UINT16_C(n)
#define WHEEL_PRIu PRIu16
#define WHEEL_PRIx PRIx16
typedef uint16_t wheel_t;
#elif WHEEL_BIT == 3
#define WHEEL_C(n) UINT8_C(n)
#define WHEEL_PRIu PRIu8
#define WHEEL_PRIx PRIx8
typedef uint8_t wheel_t;
#else
#error invalid WHEEL_BIT value
#endif
static inline wheel_t rotl(const wheel_t v, int c) {
if (!(c &= (sizeof v * CHAR_BIT - 1)))
return v;
return (v << c) | (v >> (sizeof v * CHAR_BIT - c));
} /* rotl() */
static inline wheel_t rotr(const wheel_t v, int c) {
if (!(c &= (sizeof v * CHAR_BIT - 1)))
return v;
return (v >> c) | (v << (sizeof v * CHAR_BIT - c));
} /* rotr() */
/*
* T I M E R R O U T I N E S
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
TAILQ_HEAD(timeout_list, timeout);
struct timeouts {
struct timeout_list wheel[WHEEL_NUM][WHEEL_LEN], expired;
wheel_t pending[WHEEL_NUM];
timeout_t curtime;
timeout_t hertz;
}; /* struct timeouts */
static struct timeouts *timeouts_init(struct timeouts *T, timeout_t hz) {
unsigned i, j;
for (i = 0; i < countof(T->wheel); i++) {
for (j = 0; j < countof(T->wheel[i]); j++) {
TAILQ_INIT(&T->wheel[i][j]);
}
}
TAILQ_INIT(&T->expired);
for (i = 0; i < countof(T->pending); i++) {
T->pending[i] = 0;
}
T->curtime = 0;
T->hertz = (hz)? hz : TIMEOUT_mHZ;
return T;
} /* timeouts_init() */
TIMEOUT_PUBLIC struct timeouts *timeouts_open(timeout_t hz, int *error) {
struct timeouts *T;
if ((T = malloc(sizeof *T)))
return timeouts_init(T, hz);
*error = errno;
return NULL;
} /* timeouts_open() */
static void timeouts_reset(struct timeouts *T) {
struct timeout_list reset;
struct timeout *to;
unsigned i, j;
TAILQ_INIT(&reset);
for (i = 0; i < countof(T->wheel); i++) {
for (j = 0; j < countof(T->wheel[i]); j++) {
TAILQ_CONCAT(&reset, &T->wheel[i][j], tqe);
}
}
TAILQ_CONCAT(&reset, &T->expired, tqe);
TAILQ_FOREACH(to, &reset, tqe) {
to->pending = NULL;
TO_SET_TIMEOUTS(to, NULL);
}
} /* timeouts_reset() */
TIMEOUT_PUBLIC void timeouts_close(struct timeouts *T) {
/*
* NOTE: Delete installed timeouts so timeout_pending() and
* timeout_expired() worked as expected.
*/
timeouts_reset(T);
free(T);
} /* timeouts_close() */
TIMEOUT_PUBLIC timeout_t timeouts_hz(struct timeouts *T) {
return T->hertz;
} /* timeouts_hz() */
TIMEOUT_PUBLIC void timeouts_del(struct timeouts *T, struct timeout *to) {
if (to->pending) {
TAILQ_REMOVE(to->pending, to, tqe);
if (to->pending != &T->expired && TAILQ_EMPTY(to->pending)) {
ptrdiff_t index = to->pending - &T->wheel[0][0];
int wheel = index / WHEEL_LEN;
int slot = index % WHEEL_LEN;
T->pending[wheel] &= ~(WHEEL_C(1) << slot);
}
to->pending = NULL;
TO_SET_TIMEOUTS(to, NULL);
}
} /* timeouts_del() */
static inline reltime_t timeout_rem(struct timeouts *T, struct timeout *to) {
return to->expires - T->curtime;
} /* timeout_rem() */
static inline int timeout_wheel(timeout_t timeout) {
/* must be called with timeout != 0, so fls input is nonzero */
return (fls(MIN(timeout, TIMEOUT_MAX)) - 1) / WHEEL_BIT;
} /* timeout_wheel() */
static inline int timeout_slot(int wheel, timeout_t expires) {
return WHEEL_MASK & ((expires >> (wheel * WHEEL_BIT)) - !!wheel);
} /* timeout_slot() */
static void timeouts_sched(struct timeouts *T, struct timeout *to, timeout_t expires) {
timeout_t rem;
int wheel, slot;
timeouts_del(T, to);
to->expires = expires;
TO_SET_TIMEOUTS(to, T);
if (expires > T->curtime) {
rem = timeout_rem(T, to);
/* rem is nonzero since:
* rem == timeout_rem(T,to),
* == to->expires - T->curtime
* and above we have expires > T->curtime.
*/
wheel = timeout_wheel(rem);
slot = timeout_slot(wheel, to->expires);
to->pending = &T->wheel[wheel][slot];
TAILQ_INSERT_TAIL(to->pending, to, tqe);
T->pending[wheel] |= WHEEL_C(1) << slot;
} else {
to->pending = &T->expired;
TAILQ_INSERT_TAIL(to->pending, to, tqe);
}
} /* timeouts_sched() */
#ifndef TIMEOUT_DISABLE_INTERVALS
static void timeouts_readd(struct timeouts *T, struct timeout *to) {
to->expires += to->interval;
if (to->expires <= T->curtime) {
/* If we've missed the next firing of this timeout, reschedule
* it to occur at the next multiple of its interval after
* the last time that it fired.
*/
timeout_t n = T->curtime - to->expires;
timeout_t r = n % to->interval;
to->expires = T->curtime + (to->interval - r);
}
timeouts_sched(T, to, to->expires);
} /* timeouts_readd() */
#endif
TIMEOUT_PUBLIC void timeouts_add(struct timeouts *T, struct timeout *to, timeout_t timeout) {
#ifndef TIMEOUT_DISABLE_INTERVALS
if (to->flags & TIMEOUT_INT)
to->interval = MAX(1, timeout);
#endif
if (to->flags & TIMEOUT_ABS)
timeouts_sched(T, to, timeout);
else
timeouts_sched(T, to, T->curtime + timeout);
} /* timeouts_add() */
TIMEOUT_PUBLIC void timeouts_update(struct timeouts *T, abstime_t curtime) {
timeout_t elapsed = curtime - T->curtime;
struct timeout_list todo;
int wheel;
TAILQ_INIT(&todo);
/*
* There's no avoiding looping over every wheel. It's best to keep
* WHEEL_NUM smallish.
*/
for (wheel = 0; wheel < WHEEL_NUM; wheel++) {
wheel_t pending;
/*
* Calculate the slots expiring in this wheel
*
* If the elapsed time is greater than the maximum period of
* the wheel, mark every position as expiring.
*
* Otherwise, to determine the expired slots fill in all the
* bits between the last slot processed and the current
* slot, inclusive of the last slot. We'll bitwise-AND this
* with our pending set below.
*
* If a wheel rolls over, force a tick of the next higher
* wheel.
*/
if ((elapsed >> (wheel * WHEEL_BIT)) > WHEEL_MAX) {
pending = (wheel_t)~WHEEL_C(0);
} else {
wheel_t _elapsed = WHEEL_MASK & (elapsed >> (wheel * WHEEL_BIT));
int oslot, nslot;
/*
* TODO: It's likely that at least one of the
* following three bit fill operations is redundant
* or can be replaced with a simpler operation.
*/
oslot = WHEEL_MASK & (T->curtime >> (wheel * WHEEL_BIT));
pending = rotl(((UINT64_C(1) << _elapsed) - 1), oslot);
nslot = WHEEL_MASK & (curtime >> (wheel * WHEEL_BIT));
pending |= rotr(rotl(((WHEEL_C(1) << _elapsed) - 1), nslot), _elapsed);
pending |= WHEEL_C(1) << nslot;
}
while (pending & T->pending[wheel]) {
/* ctz input cannot be zero: loop condition. */
int slot = ctz(pending & T->pending[wheel]);
TAILQ_CONCAT(&todo, &T->wheel[wheel][slot], tqe);
T->pending[wheel] &= ~(UINT64_C(1) << slot);
}
if (!(0x1 & pending))
break; /* break if we didn't wrap around end of wheel */
/* if we're continuing, the next wheel must tick at least once */
elapsed = MAX(elapsed, (WHEEL_LEN << (wheel * WHEEL_BIT)));
}
T->curtime = curtime;
while (!TAILQ_EMPTY(&todo)) {
struct timeout *to = TAILQ_FIRST(&todo);
TAILQ_REMOVE(&todo, to, tqe);
to->pending = NULL;
timeouts_sched(T, to, to->expires);
}
return;
} /* timeouts_update() */
TIMEOUT_PUBLIC timeout_t timeouts_get_curtime(struct timeouts *T) {
return T->curtime;
} /* timeouts_get_curtime() */
TIMEOUT_PUBLIC void timeouts_step(struct timeouts *T, reltime_t elapsed) {
timeouts_update(T, T->curtime + elapsed);
} /* timeouts_step() */
TIMEOUT_PUBLIC bool timeouts_pending(struct timeouts *T) {
wheel_t pending = 0;
int wheel;
for (wheel = 0; wheel < WHEEL_NUM; wheel++) {
pending |= T->pending[wheel];
}
return !!pending;
} /* timeouts_pending() */
TIMEOUT_PUBLIC bool timeouts_expired(struct timeouts *T) {
return !TAILQ_EMPTY(&T->expired);
} /* timeouts_expired() */
/*
* Calculate the interval before needing to process any timeouts pending on
* any wheel.
*
* (This is separated from the public API routine so we can evaluate our
* wheel invariant assertions irrespective of the expired queue.)
*
* This might return a timeout value sooner than any installed timeout if
* only higher-order wheels have timeouts pending. We can only know when to
* process a wheel, not precisely when a timeout is scheduled. Our timeout
* accuracy could be off by 2^(N*M)-1 units where N is the wheel number and
* M is WHEEL_BIT. Only timeouts which have fallen through to wheel 0 can be
* known exactly.
*
* We should never return a timeout larger than the lowest actual timeout.
*/
static timeout_t timeouts_int(struct timeouts *T) {
timeout_t timeout = ~TIMEOUT_C(0), _timeout;
timeout_t relmask;
int wheel, slot;
relmask = 0;
for (wheel = 0; wheel < WHEEL_NUM; wheel++) {
if (T->pending[wheel]) {
slot = WHEEL_MASK & (T->curtime >> (wheel * WHEEL_BIT));
/* ctz input cannot be zero: T->pending[wheel] is
* nonzero, so rotr() is nonzero. */
_timeout = (ctz(rotr(T->pending[wheel], slot)) + !!wheel) << (wheel * WHEEL_BIT);
/* +1 to higher order wheels as those timeouts are one rotation in the future (otherwise they'd be on a lower wheel or expired) */
_timeout -= relmask & T->curtime;
/* reduce by how much lower wheels have progressed */
timeout = MIN(_timeout, timeout);
}
relmask <<= WHEEL_BIT;
relmask |= WHEEL_MASK;
}
return timeout;
} /* timeouts_int() */
/*
* Calculate the interval our caller can wait before needing to process
* events.
*/
TIMEOUT_PUBLIC timeout_t timeouts_timeout(struct timeouts *T) {
if (!TAILQ_EMPTY(&T->expired))
return 0;
return timeouts_int(T);
} /* timeouts_timeout() */
TIMEOUT_PUBLIC struct timeout *timeouts_get(struct timeouts *T) {
if (!TAILQ_EMPTY(&T->expired)) {
struct timeout *to = TAILQ_FIRST(&T->expired);
TAILQ_REMOVE(&T->expired, to, tqe);
to->pending = NULL;
TO_SET_TIMEOUTS(to, NULL);
#ifndef TIMEOUT_DISABLE_INTERVALS
if ((to->flags & TIMEOUT_INT) && to->interval > 0)
timeouts_readd(T, to);
#endif
return to;
} else {
return 0;
}
} /* timeouts_get() */
/*
* Use dumb looping to locate the earliest timeout pending on the wheel so
* our invariant assertions can check the result of our optimized code.
*/
static struct timeout *timeouts_min(struct timeouts *T) {
struct timeout *to, *min = NULL;
unsigned i, j;
for (i = 0; i < countof(T->wheel); i++) {
for (j = 0; j < countof(T->wheel[i]); j++) {
TAILQ_FOREACH(to, &T->wheel[i][j], tqe) {
if (!min || to->expires < min->expires)
min = to;
}
}
}
return min;
} /* timeouts_min() */
/*
* Check some basic algorithm invariants. If these invariants fail then
* something is definitely broken.
*/
#define report(...) do { \
if ((fp)) \
fprintf(fp, __VA_ARGS__); \
} while (0)
#define check(expr, ...) do { \
if (!(expr)) { \
report(__VA_ARGS__); \
return 0; \
} \
} while (0)
TIMEOUT_PUBLIC bool timeouts_check(struct timeouts *T, FILE *fp) {
timeout_t timeout;
struct timeout *to;
if ((to = timeouts_min(T))) {
check(to->expires > T->curtime, "missed timeout (expires:%" TIMEOUT_PRIu " <= curtime:%" TIMEOUT_PRIu ")\n", to->expires, T->curtime);
timeout = timeouts_int(T);
check(timeout <= to->expires - T->curtime, "wrong soft timeout (soft:%" TIMEOUT_PRIu " > hard:%" TIMEOUT_PRIu ") (expires:%" TIMEOUT_PRIu "; curtime:%" TIMEOUT_PRIu ")\n", timeout, (to->expires - T->curtime), to->expires, T->curtime);
timeout = timeouts_timeout(T);
check(timeout <= to->expires - T->curtime, "wrong soft timeout (soft:%" TIMEOUT_PRIu " > hard:%" TIMEOUT_PRIu ") (expires:%" TIMEOUT_PRIu "; curtime:%" TIMEOUT_PRIu ")\n", timeout, (to->expires - T->curtime), to->expires, T->curtime);
} else {
timeout = timeouts_timeout(T);
if (!TAILQ_EMPTY(&T->expired))
check(timeout == 0, "wrong soft timeout (soft:%" TIMEOUT_PRIu " != hard:%" TIMEOUT_PRIu ")\n", timeout, TIMEOUT_C(0));
else
check(timeout == ~TIMEOUT_C(0), "wrong soft timeout (soft:%" TIMEOUT_PRIu " != hard:%" TIMEOUT_PRIu ")\n", timeout, ~TIMEOUT_C(0));
}
return 1;
} /* timeouts_check() */
#define ENTER \
do { \
static const int pc0 = __LINE__; \
switch (pc0 + it->pc) { \
case __LINE__: (void)0
#define SAVE_AND_DO(do_statement) \
do { \
it->pc = __LINE__ - pc0; \
do_statement; \
case __LINE__: (void)0; \
} while (0)
#define YIELD(rv) \
SAVE_AND_DO(return (rv))
#define LEAVE \
SAVE_AND_DO(break); \
} \
} while (0)
TIMEOUT_PUBLIC struct timeout *timeouts_next(struct timeouts *T, struct timeouts_it *it) {
struct timeout *to;
ENTER;
if (it->flags & TIMEOUTS_EXPIRED) {
if (it->flags & TIMEOUTS_CLEAR) {
while ((to = timeouts_get(T))) {
YIELD(to);
}
} else {
TAILQ_FOREACH_SAFE(to, &T->expired, tqe, it->to) {
YIELD(to);
}
}
}
if (it->flags & TIMEOUTS_PENDING) {
for (it->i = 0; it->i < countof(T->wheel); it->i++) {
for (it->j = 0; it->j < countof(T->wheel[it->i]); it->j++) {
TAILQ_FOREACH_SAFE(to, &T->wheel[it->i][it->j], tqe, it->to) {
YIELD(to);
}
}
}
}
LEAVE;
return NULL;
} /* timeouts_next */
#undef LEAVE
#undef YIELD
#undef SAVE_AND_DO
#undef ENTER
/*
* T I M E O U T R O U T I N E S
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
TIMEOUT_PUBLIC struct timeout *timeout_init(struct timeout *to, int flags) {
memset(to, 0, sizeof *to);
to->flags = flags;
return to;
} /* timeout_init() */
#ifndef TIMEOUT_DISABLE_RELATIVE_ACCESS
TIMEOUT_PUBLIC bool timeout_pending(struct timeout *to) {
return to->pending && to->pending != &to->timeouts->expired;
} /* timeout_pending() */
TIMEOUT_PUBLIC bool timeout_expired(struct timeout *to) {
return to->pending && to->pending == &to->timeouts->expired;
} /* timeout_expired() */
TIMEOUT_PUBLIC void timeout_del(struct timeout *to) {
timeouts_del(to->timeouts, to);
} /* timeout_del() */
#endif
/*
* V E R S I O N I N T E R F A C E S
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
TIMEOUT_PUBLIC int timeout_version(void) {
return TIMEOUT_VERSION;
} /* timeout_version() */
TIMEOUT_PUBLIC const char *timeout_vendor(void) {
return TIMEOUT_VENDOR;
} /* timeout_version() */
TIMEOUT_PUBLIC int timeout_v_rel(void) {
return TIMEOUT_V_REL;
} /* timeout_version() */
TIMEOUT_PUBLIC int timeout_v_abi(void) {
return TIMEOUT_V_ABI;
} /* timeout_version() */
TIMEOUT_PUBLIC int timeout_v_api(void) {
return TIMEOUT_V_API;
} /* timeout_version() */
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