added 'activeProducer' feature

malebolgia.nimble

@@ -1,10 +1,10 @@
 # Package
 
-version       = "1.3.1"
-author        = "Araq"
-description   = "Malebolgia creates new spawns. Experiments with thread pools and related APIs."
-license       = "MIT"
-srcDir        = "src"
+version = "1.3.2"
+author = "Araq"
+description = "Malebolgia creates new spawns. Experiments with thread pools and related APIs."
+license = "MIT"
+srcDir = "src"
 
 
 # Dependencies

src/malebolgia.nim

@@ -14,22 +14,26 @@
     runningTasks: int
     stopToken: Atomic[bool]
     shouldEndAt: Time
-    usesTimeout: bool
+    usesTimeout, activeProducer: bool
 
 proc `=destroy`(m: var Master) {.inline.} =
   deinitCond(m.c)
   deinitLock(m.L)
 
 proc `=copy`(dest: var Master; src: Master) {.error.}
 proc `=sink`(dest: var Master; src: Master) {.error.}
 
-proc createMaster*(timeout = default(Duration)): Master =
+proc createMaster*(timeout = default(Duration); activeProducer = false): Master =
+  ## Set `activeProducer` to true to prevent the master thread from
+  ## running a task directly.
+  ## But beware! This can introduce deadlocks for recursive loads!
   result = default(Master)
   initCond(result.c)
   initLock(result.L)
   if timeout != default(Duration):
     result.usesTimeout = true
     result.shouldEndAt = getTime() + timeout
+  result.activeProducer = activeProducer
 
 proc cancel*(m: var Master) =
   ## Try to stop all running tasks immediately.
@@ -163,17 +167,20 @@
   deinitCond(chan.spaceAvailable)
   deinitLock(chan.L)
 
+proc shouldSend(master: var Master): bool {.inline.} =
+  master.activeProducer or busyThreads.load(moRelaxed) < ThreadPoolSize-1
+
 template spawnImplRes[T](master: var Master; fn: typed; res: T) =
   if stillHaveTime(master):
-    if busyThreads.load(moRelaxed) < ThreadPoolSize-1:
+    if shouldSend(master):
       taskCreated master
       send PoolTask(m: addr(master), t: toTask(fn), result: addr res)
     else:
       res = fn
 
 template spawnImplNoRes(master: var Master; fn: typed) =
   if stillHaveTime(master):
-    if busyThreads.load(moRelaxed) < ThreadPoolSize-1:
+    if shouldSend(master):
       taskCreated master
       send PoolTask(m: addr(master), t: toTask(fn), result: nil)
     else: