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added 'fence' instructions to the barrier

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This commit is contained in:
Araq 2014-06-06 02:05:17 +02:00
commit b7cbb08f99
3 changed files with 24 additions and 39 deletions
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25
lib/pure/concurrency/threadpool.nim
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@ -53,12 +53,15 @@ type
interest: bool ## wether the master is interested in the "all done" event
proc barrierEnter(b: ptr Barrier) {.compilerProc, inline.} =
## due to the signaling between threads, it is ensured we are the only
## one with access to 'entered' so we don't need 'atomicInc' here:
# due to the signaling between threads, it is ensured we are the only
# one with access to 'entered' so we don't need 'atomicInc' here:
inc b.entered
# also we need no 'fence' instructions here as soon 'nimArgsPassingDone'
# will be called which already will perform a fence for us.
proc barrierLeave(b: ptr Barrier) {.compilerProc, inline.} =
atomicInc b.left
when not defined(x86): fence()
if b.interest and b.left == b.entered: signal(b.cv)
proc openBarrier(b: ptr Barrier) {.compilerProc, inline.} =
@ -67,10 +70,12 @@ proc openBarrier(b: ptr Barrier) {.compilerProc, inline.} =
b.interest = false
proc closeBarrier(b: ptr Barrier) {.compilerProc.} =
fence()
if b.left != b.entered:
b.cv = createCondVar()
b.interest = true # XXX we really need to ensure no re-orderings are done
# by the C compiler here
fence()
b.interest = true
fence()
while b.left != b.entered: await(b.cv)
destroyCondVar(b.cv)
@ -207,9 +212,9 @@ proc `^`*[T](prom: Promise[T]): T =
result = prom.blob
proc awaitAny*(promises: openArray[RawPromise]): int =
# awaits any of the given promises. Returns the index of one promise for which
## a value arrived. A promise only supports one call to 'awaitAny' at the
## same time. That means if you await([a,b]) and await([b,c]) the second
## awaits any of the given promises. Returns the index of one promise for
## which a value arrived. A promise only supports one call to 'awaitAny' at
## the same time. That means if you await([a,b]) and await([b,c]) the second
## call will only await 'c'. If there is no promise left to be able to wait
## on, -1 is returned.
## **Note**: This results in non-deterministic behaviour and so should be
@ -294,14 +299,16 @@ proc preferSpawn*(): bool =
proc spawn*(call: expr): expr {.magic: "Spawn".}
## always spawns a new task, so that the 'call' is never executed on
## the calling thread. 'call' has to be proc call 'p(...)' where 'p'
## is gcsafe and has 'void' as the return type.
## is gcsafe and has a return type that is either 'void' or compatible
## with ``Promise[T]``.
template spawnX*(call: expr): expr =
## spawns a new task if a CPU core is ready, otherwise executes the
## call in the calling thread. Usually it is advised to
## use 'spawn' in order to not block the producer for an unknown
## amount of time. 'call' has to be proc call 'p(...)' where 'p'
## is gcsafe and has 'void' as the return type.
## is gcsafe and has a return type that is either 'void' or compatible
## with ``Promise[T]``.
(if preferSpawn(): spawn call else: call)
proc parallel*(body: stmt) {.magic: "Parallel".}