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sync: support concurrent selects on same channel(s) (#7415)

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This commit is contained in:
Uwe Krüger
2020-12-20 04:52:40 +01:00
committed by GitHub
parent b29bcb3fbe
commit af9766a7d6
2 changed files with 88 additions and 9 deletions
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22
vlib/sync/channels.v
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@@ -511,20 +511,18 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
mut subscr := []Subscription{len: channels.len}
sem := new_semaphore()
for i, ch in channels {
subscr[i].sem = sem
if dir[i] == .push {
mut null16 := u16(0)
for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
null16 = u16(0)
}
subscr[i].sem = sem
subscr[i].prev = &ch.write_subscriber
unsafe {
subscr[i].nxt = C.atomic_exchange_ptr(&ch.write_subscriber, &subscr[i])
}
if voidptr(subscr[i].nxt) != voidptr(0) {
unsafe {
subscr[i].nxt.prev = &subscr[i]
}
subscr[i].nxt.prev = &subscr[i].nxt
}
C.atomic_store_u16(&ch.write_sub_mtx, u16(0))
} else {
@@ -532,13 +530,12 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
null16 = u16(0)
}
subscr[i].sem = sem
subscr[i].prev = &ch.read_subscriber
unsafe {
subscr[i].nxt = C.atomic_exchange_ptr(&ch.read_subscriber, &subscr[i])
}
if voidptr(subscr[i].nxt) != voidptr(0) {
unsafe { subscr[i].nxt.prev = &subscr[i] }
subscr[i].nxt.prev = &subscr[i].nxt
}
C.atomic_store_u16(&ch.read_sub_mtx, u16(0))
}
@@ -577,7 +574,8 @@ pub fn channel_select(mut channels []&Channel, dir []Direction, mut objrefs []vo
}
if timeout == 0 {
goto restore
} else if timeout > 0 {
}
if timeout > 0 {
remaining := timeout - stopwatch.elapsed()
if !sem.timed_wait(remaining) {
goto restore
@@ -594,8 +592,11 @@ restore:
for !C.atomic_compare_exchange_weak_u16(&ch.write_sub_mtx, &null16, u16(1)) {
null16 = u16(0)
}
subscr[i].prev = subscr[i].nxt
unsafe {
*subscr[i].prev = subscr[i].nxt
}
if subscr[i].nxt != 0 {
subscr[i].nxt.prev = subscr[i].prev
// just in case we have missed a semaphore during restore
subscr[i].nxt.sem.post()
}
@@ -605,8 +606,11 @@ restore:
for !C.atomic_compare_exchange_weak_u16(&ch.read_sub_mtx, &null16, u16(1)) {
null16 = u16(0)
}
subscr[i].prev = subscr[i].nxt
unsafe {
*subscr[i].prev = subscr[i].nxt
}
if subscr[i].nxt != 0 {
subscr[i].nxt.prev = subscr[i].prev
subscr[i].nxt.sem.post()
}
C.atomic_store_u16(&ch.read_sub_mtx, u16(0))