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Make extent_dss use C11-style atomics

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David Goldblatt 2017-04-04 17:58:06 -07:00 committed by David Goldblatt
parent 92aafb0efe
commit 55d992c48c
1 changed files with 21 additions and 15 deletions
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36
src/extent_dss.c
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@ -18,14 +18,15 @@ const char *dss_prec_names[] = {
* guarantee that sizeof(dss_prec_t) is the same as sizeof(unsigned), and we use * guarantee that sizeof(dss_prec_t) is the same as sizeof(unsigned), and we use
* atomic operations to synchronize the setting. * atomic operations to synchronize the setting.
*/ */
static unsigned dss_prec_default = (unsigned)DSS_PREC_DEFAULT; static atomic_u_t dss_prec_default = ATOMIC_INIT(
(unsigned)DSS_PREC_DEFAULT);
/* Base address of the DSS. */ /* Base address of the DSS. */
static void *dss_base; static void *dss_base;
/* Atomic boolean indicating whether the DSS is exhausted. */ /* Atomic boolean indicating whether the DSS is exhausted. */
static unsigned dss_exhausted; static atomic_b_t dss_exhausted;
/* Atomic current upper limit on DSS addresses. */ /* Atomic current upper limit on DSS addresses. */
static void *dss_max; static atomic_p_t dss_max;
/******************************************************************************/ /******************************************************************************/
@ -46,7 +47,7 @@ extent_dss_prec_get(void) {
if (!have_dss) { if (!have_dss) {
return dss_prec_disabled; return dss_prec_disabled;
} }
ret = (dss_prec_t)atomic_read_u(&dss_prec_default); ret = (dss_prec_t)atomic_load_u(&dss_prec_default, ATOMIC_ACQUIRE);
return ret; return ret;
} }
@ -55,7 +56,7 @@ extent_dss_prec_set(dss_prec_t dss_prec) {
if (!have_dss) { if (!have_dss) {
return (dss_prec != dss_prec_disabled); return (dss_prec != dss_prec_disabled);
} }
atomic_write_u(&dss_prec_default, (unsigned)dss_prec); atomic_store_u(&dss_prec_default, (unsigned)dss_prec, ATOMIC_RELEASE);
return false; return false;
} }
@ -69,7 +70,7 @@ extent_dss_max_update(void *new_addr) {
*/ */
spin_t spinner = SPIN_INITIALIZER; spin_t spinner = SPIN_INITIALIZER;
while (true) { while (true) {
void *max_prev = atomic_read_p(&dss_max); void *max_prev = atomic_load_p(&dss_max, ATOMIC_RELAXED);
max_cur = extent_dss_sbrk(0); max_cur = extent_dss_sbrk(0);
if ((uintptr_t)max_prev > (uintptr_t)max_cur) { if ((uintptr_t)max_prev > (uintptr_t)max_cur) {
@ -80,7 +81,8 @@ extent_dss_max_update(void *new_addr) {
spin_adaptive(&spinner); spin_adaptive(&spinner);
continue; continue;
} }
if (!atomic_cas_p(&dss_max, max_prev, max_cur)) { if (atomic_compare_exchange_weak_p(&dss_max, &max_prev,
max_cur, ATOMIC_ACQ_REL, ATOMIC_RELAXED)) {
break; break;
} }
} }
@ -114,7 +116,7 @@ extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
return NULL; return NULL;
} }
if (!atomic_read_u(&dss_exhausted)) { if (!atomic_load_b(&dss_exhausted, ATOMIC_ACQUIRE)) {
/* /*
* The loop is necessary to recover from races with other * The loop is necessary to recover from races with other
* threads that are using the DSS for something other than * threads that are using the DSS for something other than
@ -167,7 +169,8 @@ extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
* DSS while dss_max is greater than the current DSS * DSS while dss_max is greater than the current DSS
* max reported by sbrk(0). * max reported by sbrk(0).
*/ */
if (atomic_cas_p(&dss_max, max_cur, dss_next)) { if (!atomic_compare_exchange_weak_p(&dss_max, &max_cur,
dss_next, ATOMIC_ACQ_REL, ATOMIC_RELAXED)) {
continue; continue;
} }
@ -207,10 +210,12 @@ extent_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
* succeeded since this invocation started, in which * succeeded since this invocation started, in which
* case rollback is not necessary. * case rollback is not necessary.
*/ */
atomic_cas_p(&dss_max, dss_next, max_cur); atomic_compare_exchange_strong_p(&dss_max, &dss_next,
max_cur, ATOMIC_ACQ_REL, ATOMIC_RELAXED);
if (dss_prev == (void *)-1) { if (dss_prev == (void *)-1) {
/* OOM. */ /* OOM. */
atomic_write_u(&dss_exhausted, (unsigned)true); atomic_store_b(&dss_exhausted, true,
ATOMIC_RELEASE);
goto label_oom; goto label_oom;
} }
} }
@ -230,7 +235,8 @@ bool
extent_in_dss(void *addr) { extent_in_dss(void *addr) {
cassert(have_dss); cassert(have_dss);
return extent_in_dss_helper(addr, atomic_read_p(&dss_max)); return extent_in_dss_helper(addr, atomic_load_p(&dss_max,
ATOMIC_ACQUIRE));
} }
bool bool
@ -244,7 +250,7 @@ extent_dss_mergeable(void *addr_a, void *addr_b) {
return true; return true;
} }
max = atomic_read_p(&dss_max); max = atomic_load_p(&dss_max, ATOMIC_ACQUIRE);
return (extent_in_dss_helper(addr_a, max) == return (extent_in_dss_helper(addr_a, max) ==
extent_in_dss_helper(addr_b, max)); extent_in_dss_helper(addr_b, max));
} }
@ -254,8 +260,8 @@ extent_dss_boot(void) {
cassert(have_dss); cassert(have_dss);
dss_base = extent_dss_sbrk(0); dss_base = extent_dss_sbrk(0);
dss_exhausted = (unsigned)(dss_base == (void *)-1); atomic_store_b(&dss_exhausted, dss_base == (void *)-1, ATOMIC_RELAXED);
dss_max = dss_base; atomic_store_p(&dss_max, dss_base, ATOMIC_RELAXED);
} }
/******************************************************************************/ /******************************************************************************/