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Code Issues Releases Wiki Activity

Use C11's stdatomic.h instead of isc_atomic where available

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This commit is contained in:
Mukund Sivaraman
2017-09-19 15:42:54 +05:30
parent fb088a00cf
commit 404c9b1c53
10 changed files with 315 additions and 49 deletions
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177
lib/isc/rwlock.c
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@@ -39,7 +39,7 @@
#define RWLOCK_MAX_ADAPTIVE_COUNT 100
#endif
#if defined(ISC_PLATFORM_HAVEXADD) && defined(ISC_PLATFORM_HAVECMPXCHG)
#if defined(ISC_RWLOCK_USEATOMIC)
static isc_result_t
isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type);
#endif
@@ -50,7 +50,7 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type);
static void
print_lock(const char *operation, isc_rwlock_t *rwl, isc_rwlocktype_t type) {
#if defined(ISC_PLATFORM_HAVEXADD) && defined(ISC_PLATFORM_HAVECMPXCHG)
#if defined(ISC_RWLOCK_USEATOMIC)
fprintf(stderr,
isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_PRINTLOCK2,
@@ -105,7 +105,7 @@ isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
rwl->magic = 0;
rwl->spins = 0;
#if defined(ISC_PLATFORM_HAVEXADD) && defined(ISC_PLATFORM_HAVECMPXCHG)
#if defined(ISC_RWLOCK_USEATOMIC)
rwl->write_requests = 0;
rwl->write_completions = 0;
rwl->cnt_and_flag = 0;
@@ -174,7 +174,7 @@ void
isc_rwlock_destroy(isc_rwlock_t *rwl) {
REQUIRE(VALID_RWLOCK(rwl));
#if defined(ISC_PLATFORM_HAVEXADD) && defined(ISC_PLATFORM_HAVECMPXCHG)
#if defined(ISC_RWLOCK_USEATOMIC)
REQUIRE(rwl->write_requests == rwl->write_completions &&
rwl->cnt_and_flag == 0 && rwl->readers_waiting == 0);
#else
@@ -191,7 +191,7 @@ isc_rwlock_destroy(isc_rwlock_t *rwl) {
DESTROYLOCK(&rwl->lock);
}
#if defined(ISC_PLATFORM_HAVEXADD) && defined(ISC_PLATFORM_HAVECMPXCHG)
#if defined(ISC_RWLOCK_USEATOMIC)
/*
* When some architecture-dependent atomic operations are available,
@@ -281,7 +281,13 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
UNLOCK(&rwl->lock);
}
#if defined(ISC_RWLOCK_USESTDATOMIC)
cntflag = atomic_fetch_add_explicit(&rwl->cnt_and_flag,
READER_INCR,
memory_order_relaxed);
#else
cntflag = isc_atomic_xadd(&rwl->cnt_and_flag, READER_INCR);
#endif
POST(cntflag);
while (1) {
if ((rwl->cnt_and_flag & WRITER_ACTIVE) == 0)
@@ -331,7 +337,12 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
isc_int32_t prev_writer;
/* enter the waiting queue, and wait for our turn */
#if defined(ISC_RWLOCK_USESTDATOMIC)
prev_writer = atomic_fetch_add_explicit(&rwl->write_requests, 1,
memory_order_relaxed);
#else
prev_writer = isc_atomic_xadd(&rwl->write_requests, 1);
#endif
while (rwl->write_completions != prev_writer) {
LOCK(&rwl->lock);
if (rwl->write_completions != prev_writer) {
@@ -344,9 +355,18 @@ isc__rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
}
while (1) {
cntflag = isc_atomic_cmpxchg(&rwl->cnt_and_flag, 0,
WRITER_ACTIVE);
if (cntflag == 0)
#if defined(ISC_RWLOCK_USESTDATOMIC)
atomic_int_fast32_t cntflag2 = 0;
atomic_compare_exchange_strong_explicit
(&rwl->cnt_and_flag, &cntflag2, WRITER_ACTIVE,
memory_order_relaxed, memory_order_relaxed);
#else
isc_int32_t cntflag2;
cntflag2 = isc_atomic_cmpxchg(&rwl->cnt_and_flag, 0,
WRITER_ACTIVE);
#endif
if (cntflag2 == 0)
break;
/* Another active reader or writer is working. */
@@ -409,14 +429,26 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (ISC_R_LOCKBUSY);
/* Otherwise, be ready for reading. */
#if defined(ISC_RWLOCK_USESTDATOMIC)
cntflag = atomic_fetch_add_explicit(&rwl->cnt_and_flag,
READER_INCR,
memory_order_relaxed);
#else
cntflag = isc_atomic_xadd(&rwl->cnt_and_flag, READER_INCR);
#endif
if ((cntflag & WRITER_ACTIVE) != 0) {
/*
* A writer is working. We lose, and cancel the read
* request.
*/
#if defined(ISC_RWLOCK_USESTDATOMIC)
cntflag = atomic_fetch_sub_explicit
(&rwl->cnt_and_flag, READER_INCR,
memory_order_relaxed);
#else
cntflag = isc_atomic_xadd(&rwl->cnt_and_flag,
-READER_INCR);
#endif
/*
* If no other readers are waiting and we've suspended
* new writers in this short period, wake them up.
@@ -432,16 +464,29 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
}
} else {
/* Try locking without entering the waiting queue. */
#if defined(ISC_RWLOCK_USESTDATOMIC)
atomic_int_fast32_t zero = 0;
if (!atomic_compare_exchange_strong_explicit
(&rwl->cnt_and_flag, &zero, WRITER_ACTIVE,
memory_order_relaxed, memory_order_relaxed))
return (ISC_R_LOCKBUSY);
#else
cntflag = isc_atomic_cmpxchg(&rwl->cnt_and_flag, 0,
WRITER_ACTIVE);
if (cntflag != 0)
return (ISC_R_LOCKBUSY);
#endif
/*
* XXXJT: jump into the queue, possibly breaking the writer
* order.
*/
#if defined(ISC_RWLOCK_USESTDATOMIC)
atomic_fetch_sub_explicit(&rwl->write_completions, 1,
memory_order_relaxed);
#else
(void)isc_atomic_xadd(&rwl->write_completions, -1);
#endif
rwl->write_granted++;
}
@@ -456,31 +501,60 @@ isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
isc_result_t
isc_rwlock_tryupgrade(isc_rwlock_t *rwl) {
isc_int32_t prevcnt;
REQUIRE(VALID_RWLOCK(rwl));
/* Try to acquire write access. */
prevcnt = isc_atomic_cmpxchg(&rwl->cnt_and_flag,
READER_INCR, WRITER_ACTIVE);
/*
* There must have been no writer, and there must have been at least
* one reader.
*/
INSIST((prevcnt & WRITER_ACTIVE) == 0 &&
(prevcnt & ~WRITER_ACTIVE) != 0);
#if defined(ISC_RWLOCK_USESTDATOMIC)
{
atomic_int_fast32_t reader_incr = READER_INCR;
if (prevcnt == READER_INCR) {
/* Try to acquire write access. */
atomic_compare_exchange_strong_explicit
(&rwl->cnt_and_flag, &reader_incr, WRITER_ACTIVE,
memory_order_relaxed, memory_order_relaxed);
/*
* We are the only reader and have been upgraded.
* Now jump into the head of the writer waiting queue.
* There must have been no writer, and there must have
* been at least one reader.
*/
(void)isc_atomic_xadd(&rwl->write_completions, -1);
} else
return (ISC_R_LOCKBUSY);
INSIST((reader_incr & WRITER_ACTIVE) == 0 &&
(reader_incr & ~WRITER_ACTIVE) != 0);
if (reader_incr == READER_INCR) {
/*
* We are the only reader and have been upgraded.
* Now jump into the head of the writer waiting queue.
*/
atomic_fetch_sub_explicit(&rwl->write_completions, 1,
memory_order_relaxed);
} else
return (ISC_R_LOCKBUSY);
}
#else
{
isc_int32_t prevcnt;
/* Try to acquire write access. */
prevcnt = isc_atomic_cmpxchg(&rwl->cnt_and_flag,
READER_INCR, WRITER_ACTIVE);
/*
* There must have been no writer, and there must have
* been at least one reader.
*/
INSIST((prevcnt & WRITER_ACTIVE) == 0 &&
(prevcnt & ~WRITER_ACTIVE) != 0);
if (prevcnt == READER_INCR) {
/*
* We are the only reader and have been upgraded.
* Now jump into the head of the writer waiting queue.
*/
(void)isc_atomic_xadd(&rwl->write_completions, -1);
} else
return (ISC_R_LOCKBUSY);
}
#endif
return (ISC_R_SUCCESS);
}
void
@@ -489,14 +563,33 @@ isc_rwlock_downgrade(isc_rwlock_t *rwl) {
REQUIRE(VALID_RWLOCK(rwl));
/* Become an active reader. */
prev_readers = isc_atomic_xadd(&rwl->cnt_and_flag, READER_INCR);
/* We must have been a writer. */
INSIST((prev_readers & WRITER_ACTIVE) != 0);
#if defined(ISC_RWLOCK_USESTDATOMIC)
{
/* Become an active reader. */
prev_readers = atomic_fetch_add_explicit(&rwl->cnt_and_flag,
READER_INCR,
memory_order_relaxed);
/* We must have been a writer. */
INSIST((prev_readers & WRITER_ACTIVE) != 0);
/* Complete write */
(void)isc_atomic_xadd(&rwl->cnt_and_flag, -WRITER_ACTIVE);
(void)isc_atomic_xadd(&rwl->write_completions, 1);
/* Complete write */
atomic_fetch_sub_explicit(&rwl->cnt_and_flag, WRITER_ACTIVE,
memory_order_relaxed);
atomic_fetch_add_explicit(&rwl->write_completions, 1,
memory_order_relaxed);
}
#else
{
/* Become an active reader. */
prev_readers = isc_atomic_xadd(&rwl->cnt_and_flag, READER_INCR);
/* We must have been a writer. */
INSIST((prev_readers & WRITER_ACTIVE) != 0);
/* Complete write */
(void)isc_atomic_xadd(&rwl->cnt_and_flag, -WRITER_ACTIVE);
(void)isc_atomic_xadd(&rwl->write_completions, 1);
}
#endif
/* Resume other readers */
LOCK(&rwl->lock);
@@ -517,8 +610,13 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
#endif
if (type == isc_rwlocktype_read) {
#if defined(ISC_RWLOCK_USESTDATOMIC)
prev_cnt = atomic_fetch_sub_explicit(&rwl->cnt_and_flag,
READER_INCR,
memory_order_relaxed);
#else
prev_cnt = isc_atomic_xadd(&rwl->cnt_and_flag, -READER_INCR);
#endif
/*
* If we're the last reader and any writers are waiting, wake
* them up. We need to wake up all of them to ensure the
@@ -537,8 +635,15 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
* Reset the flag, and (implicitly) tell other writers
* we are done.
*/
#if defined(ISC_RWLOCK_USESTDATOMIC)
atomic_fetch_sub_explicit(&rwl->cnt_and_flag, WRITER_ACTIVE,
memory_order_relaxed);
atomic_fetch_add_explicit(&rwl->write_completions, 1,
memory_order_relaxed);
#else
(void)isc_atomic_xadd(&rwl->cnt_and_flag, -WRITER_ACTIVE);
(void)isc_atomic_xadd(&rwl->write_completions, 1);
#endif
if (rwl->write_granted >= rwl->write_quota ||
rwl->write_requests == rwl->write_completions ||
@@ -576,7 +681,7 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (ISC_R_SUCCESS);
}
#else /* ISC_PLATFORM_HAVEXADD && ISC_PLATFORM_HAVECMPXCHG */
#else /* ISC_RWLOCK_USEATOMIC */
static isc_result_t
doit(isc_rwlock_t *rwl, isc_rwlocktype_t type, isc_boolean_t nonblock) {
@@ -782,7 +887,7 @@ isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (ISC_R_SUCCESS);
}
#endif /* ISC_PLATFORM_HAVEXADD && ISC_PLATFORM_HAVECMPXCHG */
#endif /* ISC_RWLOCK_USEATOMIC */
#else /* ISC_PLATFORM_USETHREADS */
isc_result_t