* STG execution, a pointer to the capabilitity is kept in a
* register (BaseReg; actually it is a pointer to cap->r).
*
- * Only in an SMP build will there be multiple capabilities, for
- * the threaded RTS and other non-threaded builds, there is only
- * one global capability, namely MainCapability.
+ * Only in an THREADED_RTS build will there be multiple capabilities,
+ * for non-threaded builds there is only one global capability, namely
+ * MainCapability.
*
* --------------------------------------------------------------------------*/
#include "Schedule.h"
#include "Sparks.h"
-#if !defined(SMP)
-Capability MainCapability; // for non-SMP, we have one global capability
-#endif
+// one global capability, this is the Capability for non-threaded
+// builds, and for +RTS -N1
+Capability MainCapability;
nat n_capabilities;
Capability *capabilities = NULL;
STATIC_INLINE rtsBool
anyWorkForMe( Capability *cap, Task *task )
{
- // If the run queue is not empty, then we only wake up the guy who
- // can run the thread at the head, even if there is some other
- // reason for this task to run (eg. interrupted=rtsTrue).
- if (!emptyRunQueue(cap)) {
- if (cap->run_queue_hd->bound == NULL) {
- return (task->tso == NULL);
- } else {
- return (cap->run_queue_hd->bound == task);
- }
- } else if (task->tso == NULL && !emptySparkPoolCap(cap)) {
- return rtsTrue;
+ if (task->tso != NULL) {
+ // A bound task only runs if its thread is on the run queue of
+ // the capability on which it was woken up. Otherwise, we
+ // can't be sure that we have the right capability: the thread
+ // might be woken up on some other capability, and task->cap
+ // could change under our feet.
+ return !emptyRunQueue(cap) && cap->run_queue_hd->bound == task;
+ } else {
+ // A vanilla worker task runs if either there is a lightweight
+ // thread at the head of the run queue, or the run queue is
+ // empty and (there are sparks to execute, or there is some
+ // other global condition to check, such as threads blocked on
+ // blackholes).
+ if (emptyRunQueue(cap)) {
+ return !emptySparkPoolCap(cap) || globalWorkToDo();
+ } else
+ return cap->run_queue_hd->bound == NULL;
}
- return globalWorkToDo();
}
#endif
/* ---------------------------------------------------------------------------
* Function: initCapabilities()
*
- * Purpose: set up the Capability handling. For the SMP build,
+ * Purpose: set up the Capability handling. For the THREADED_RTS build,
* we keep a table of them, the size of which is
* controlled by the user via the RTS flag -N.
*
void
initCapabilities( void )
{
-#if defined(SMP)
- nat i,n;
+#if defined(THREADED_RTS)
+ nat i;
-#ifndef REG_BaseReg
+#ifndef REG_Base
// We can't support multiple CPUs if BaseReg is not a register
if (RtsFlags.ParFlags.nNodes > 1) {
errorBelch("warning: multiple CPUs not supported in this build, reverting to 1");
}
#endif
- n_capabilities = n = RtsFlags.ParFlags.nNodes;
- capabilities = stgMallocBytes(n * sizeof(Capability), "initCapabilities");
+ n_capabilities = RtsFlags.ParFlags.nNodes;
+
+ if (n_capabilities == 1) {
+ capabilities = &MainCapability;
+ // THREADED_RTS must work on builds that don't have a mutable
+ // BaseReg (eg. unregisterised), so in this case
+ // capabilities[0] must coincide with &MainCapability.
+ } else {
+ capabilities = stgMallocBytes(n_capabilities * sizeof(Capability),
+ "initCapabilities");
+ }
- for (i = 0; i < n; i++) {
+ for (i = 0; i < n_capabilities; i++) {
initCapability(&capabilities[i], i);
}
- IF_DEBUG(scheduler, sched_belch("allocated %d capabilities", n));
-#else
+ IF_DEBUG(scheduler, sched_belch("allocated %d capabilities",
+ n_capabilities));
+
+#else /* !THREADED_RTS */
+
n_capabilities = 1;
capabilities = &MainCapability;
initCapability(&MainCapability, 0);
+
#endif
// There are no free capabilities to begin with. We will start
return;
}
- // If we have an unbound thread on the run queue, or if there's
- // anything else to do, give the Capability to a worker thread.
- if (!emptyRunQueue(cap) || !emptySparkPoolCap(cap) || globalWorkToDo()) {
- if (cap->spare_workers) {
- giveCapabilityToTask(cap,cap->spare_workers);
- // The worker Task pops itself from the queue;
- return;
- }
-
+ if (!cap->spare_workers) {
// Create a worker thread if we don't have one. If the system
// is interrupted, we only create a worker task if there
// are threads that need to be completed. If the system is
}
}
+ // If we have an unbound thread on the run queue, or if there's
+ // anything else to do, give the Capability to a worker thread.
+ if (!emptyRunQueue(cap) || !emptySparkPoolCap(cap) || globalWorkToDo()) {
+ if (cap->spare_workers) {
+ giveCapabilityToTask(cap,cap->spare_workers);
+ // The worker Task pops itself from the queue;
+ return;
+ }
+ }
+
last_free_capability = cap;
IF_DEBUG(scheduler, sched_belch("freeing capability %d", cap->no));
}
}
RELEASE_LOCK(&cap->lock);
}
+ return;
}
void
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