diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/ioq.c | 22 |
1 files changed, 11 insertions, 11 deletions
@@ -313,9 +313,11 @@ static void ioq_slot_wake(struct ioqq *ioqq, ioq_slot *slot) { cond_broadcast(&monitor->cond); } -/** Branch-free (slot & IOQ_SKIP) ? ~IOQ_BLOCKED : 0 */ -static uintptr_t ioq_skip_mask(uintptr_t slot) { - return -(slot >> IOQ_SKIP_BIT) << 1; +/** Branch-free ((slot & IOQ_SKIP) ? skip : full) & ~IOQ_BLOCKED */ +static uintptr_t ioq_slot_blend(uintptr_t slot, uintptr_t skip, uintptr_t full) { + uintptr_t mask = -(slot >> IOQ_SKIP_BIT); + uintptr_t ret = (skip & mask) | (full & ~mask); + return ret & ~IOQ_BLOCKED; } /** Push an entry into a slot. */ @@ -323,19 +325,18 @@ static bool ioq_slot_push(struct ioqq *ioqq, ioq_slot *slot, struct ioq_ent *ent uintptr_t prev = load(slot, relaxed); while (true) { - size_t skip_mask = ioq_skip_mask(prev); - size_t full_mask = ~skip_mask & ~IOQ_BLOCKED; - if (prev & full_mask) { + uintptr_t full = ioq_slot_blend(prev, 0, prev); + if (full) { // full(ptr) → wait prev = ioq_slot_wait(ioqq, slot, prev); continue; } // empty → full(ptr) - uintptr_t next = ((uintptr_t)ent >> 1) & full_mask; + uintptr_t next = (uintptr_t)ent >> 1; // skip(1) → empty // skip(n) → skip(n - 1) - next |= (prev - IOQ_SKIP_ONE) & skip_mask; + next = ioq_slot_blend(prev, prev - IOQ_SKIP_ONE, next); if (compare_exchange_weak(slot, &prev, next, release, relaxed)) { break; @@ -357,9 +358,8 @@ static struct ioq_ent *ioq_slot_pop(struct ioqq *ioqq, ioq_slot *slot, bool bloc // skip(n) → skip(n + 1) // full(ptr) → full(ptr - 1) uintptr_t next = prev + IOQ_SKIP_ONE; - // skip(n) → ~IOQ_BLOCKED // full(ptr) → 0 - next &= ioq_skip_mask(next); + next = ioq_slot_blend(next, next, 0); if (block && next) { prev = ioq_slot_wait(ioqq, slot, prev); @@ -378,7 +378,7 @@ static struct ioq_ent *ioq_slot_pop(struct ioqq *ioqq, ioq_slot *slot, bool bloc // empty → 0 // skip(n) → 0 // full(ptr) → ptr - prev &= ioq_skip_mask(~prev); + prev = ioq_slot_blend(prev, 0, prev); return (struct ioq_ent *)(prev << 1); } |