int gpr_stack_lockfree_pop(gpr_stack_lockfree *stack) {
lockfree_node head;
lockfree_node newhead;
do {
head.atm = gpr_atm_acq_load(&(stack->head.atm));
if (head.contents.index == INVALID_ENTRY_INDEX) {
return -1;
}
newhead.atm =
gpr_atm_no_barrier_load(&(stack->entries[head.contents.index].atm));
} while (!gpr_atm_no_barrier_cas(&(stack->head.atm), head.atm, newhead.atm));
#ifndef NDEBUG
/* Check for valid pop */
{
int pushed_index = head.contents.index / (8 * sizeof(gpr_atm));
int pushed_bit = head.contents.index % (8 * sizeof(gpr_atm));
gpr_atm old_val;
old_val = gpr_atm_no_barrier_fetch_add(&stack->pushed[pushed_index],
-((gpr_atm)1 << pushed_bit));
GPR_ASSERT((old_val & (((gpr_atm)1) << pushed_bit)) != 0);
}
#endif
return head.contents.index;
}
void grpc_channel_update_call_size_estimate(grpc_channel *channel,
size_t size) {
size_t cur = (size_t)gpr_atm_no_barrier_load(&channel->call_size_estimate);
if (cur < size) {
/* size grew: update estimate */
gpr_atm_no_barrier_cas(&channel->call_size_estimate, (gpr_atm)cur,
(gpr_atm)size);
/* if we lose: never mind, something else will likely update soon enough */
} else if (cur == size) {
/* no change: holding pattern */
} else if (cur > 0) {
/* size shrank: decrease estimate */
gpr_atm_no_barrier_cas(
&channel->call_size_estimate, (gpr_atm)cur,
(gpr_atm)(GPR_MIN(cur - 1, (255 * cur + size) / 256)));
/* if we lose: never mind, something else will likely update soon enough */
}
}