rts/Linker.c: distinct between DATA and CODE labels when importing
[ghc.git] / rts / Capability.c
index 3b45dec..21f63f3 100644 (file)
@@ -1,10 +1,10 @@
 /* ---------------------------------------------------------------------------
  *
- * (c) The GHC Team, 2003-2006
+ * (c) The GHC Team, 2003-2012
  *
  * Capabilities
  *
- * A Capability represent the token required to execute STG code,
+ * A Capability represents the token required to execute STG code,
  * and all the state an OS thread/task needs to run Haskell code:
  * its STG registers, a pointer to its TSO, a nursery etc. During
  * STG execution, a pointer to the capabilitity is kept in a
 #include "STM.h"
 #include "RtsUtils.h"
 
+#if !defined(mingw32_HOST_OS)
+#include "rts/IOManager.h" // for setIOManagerControlFd()
+#endif
+
+#include <string.h>
+
 // one global capability, this is the Capability for non-threaded
 // builds, and for +RTS -N1
 Capability MainCapability;
 
 nat n_capabilities = 0;
-Capability *capabilities = NULL;
+nat enabled_capabilities = 0;
+
+// The array of Capabilities.  It's important that when we need
+// to allocate more Capabilities we don't have to move the existing
+// Capabilities, because there may be pointers to them in use
+// (e.g. threads in waitForReturnCapability(), see #8209), so this is
+// an array of Capability* rather than an array of Capability.
+Capability **capabilities = NULL;
 
 // Holds the Capability which last became free.  This is used so that
 // an in-call has a chance of quickly finding a free Capability.
@@ -40,13 +53,17 @@ Capability *capabilities = NULL;
 // locking, so we don't do that.
 Capability *last_free_capability = NULL;
 
-/* GC indicator, in scope for the scheduler, init'ed to false */
-volatile StgWord waiting_for_gc = 0;
+/*
+ * Indicates that the RTS wants to synchronise all the Capabilities
+ * for some reason.  All Capabilities should stop and return to the
+ * scheduler.
+ */
+volatile StgWord pending_sync = 0;
 
 /* Let foreign code get the current Capability -- assuming there is one!
  * This is useful for unsafe foreign calls because they are called with
  * the current Capability held, but they are not passed it. For example,
- * see see the integer-gmp package which calls allocateLocal() in its
+ * see see the integer-gmp package which calls allocate() in its
  * stgAllocForGMP() function (which gets called by gmp functions).
  * */
 Capability * rts_unsafeGetMyCapability (void)
@@ -113,13 +130,13 @@ findSpark (Capability *cap)
       if (n_capabilities == 1) { return NULL; } // makes no sense...
 
       debugTrace(DEBUG_sched,
-                 "cap %d: Trying to steal work from other capabilities", 
+                 "cap %d: Trying to steal work from other capabilities",
                  cap->no);
 
       /* visit cap.s 0..n-1 in sequence until a theft succeeds. We could
       start at a random place instead of 0 as well.  */
       for ( i=0 ; i < n_capabilities ; i++ ) {
-          robbed = &capabilities[i];
+          robbed = capabilities[i];
           if (cap == robbed)  // ourselves...
               continue;
 
@@ -141,7 +158,7 @@ findSpark (Capability *cap)
           if (spark != NULL) {
               cap->spark_stats.converted++;
               traceEventSparkSteal(cap, robbed->no);
-              
+
               return spark;
           }
           // otherwise: no success, try next one
@@ -162,7 +179,7 @@ anySparks (void)
     nat i;
 
     for (i=0; i < n_capabilities; i++) {
-        if (!emptySparkPoolCap(&capabilities[i])) {
+        if (!emptySparkPoolCap(capabilities[i])) {
             return rtsTrue;
         }
     }
@@ -183,10 +200,10 @@ newReturningTask (Capability *cap, Task *task)
     ASSERT_LOCK_HELD(&cap->lock);
     ASSERT(task->next == NULL);
     if (cap->returning_tasks_hd) {
-       ASSERT(cap->returning_tasks_tl->next == NULL);
-       cap->returning_tasks_tl->next = task;
+        ASSERT(cap->returning_tasks_tl->next == NULL);
+        cap->returning_tasks_tl->next = task;
     } else {
-       cap->returning_tasks_hd = task;
+        cap->returning_tasks_hd = task;
     }
     cap->returning_tasks_tl = task;
 }
@@ -200,7 +217,7 @@ popReturningTask (Capability *cap)
     ASSERT(task);
     cap->returning_tasks_hd = task->next;
     if (!cap->returning_tasks_hd) {
-       cap->returning_tasks_tl = NULL;
+        cap->returning_tasks_tl = NULL;
     }
     task->next = NULL;
     return task;
@@ -220,6 +237,8 @@ initCapability( Capability *cap, nat i )
 
     cap->no = i;
     cap->in_haskell        = rtsFalse;
+    cap->idle              = 0;
+    cap->disabled          = rtsFalse;
 
     cap->run_queue_hd      = END_TSO_QUEUE;
     cap->run_queue_tl      = END_TSO_QUEUE;
@@ -240,23 +259,29 @@ initCapability( Capability *cap, nat i )
     cap->spark_stats.converted  = 0;
     cap->spark_stats.gcd        = 0;
     cap->spark_stats.fizzled    = 0;
+#if !defined(mingw32_HOST_OS)
+    cap->io_manager_control_wr_fd = -1;
+#endif
 #endif
+    cap->total_allocated        = 0;
 
     cap->f.stgEagerBlackholeInfo = (W_)&__stg_EAGER_BLACKHOLE_info;
     cap->f.stgGCEnter1     = (StgFunPtr)__stg_gc_enter_1;
     cap->f.stgGCFun        = (StgFunPtr)__stg_gc_fun;
 
     cap->mut_lists  = stgMallocBytes(sizeof(bdescr *) *
-                                    RtsFlags.GcFlags.generations,
-                                    "initCapability");
+                                     RtsFlags.GcFlags.generations,
+                                     "initCapability");
     cap->saved_mut_lists = stgMallocBytes(sizeof(bdescr *) *
                                           RtsFlags.GcFlags.generations,
                                           "initCapability");
 
     for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
-       cap->mut_lists[g] = NULL;
+        cap->mut_lists[g] = NULL;
     }
 
+    cap->weak_ptr_list_hd = NULL;
+    cap->weak_ptr_list_tl = NULL;
     cap->free_tvar_watch_queues = END_STM_WATCH_QUEUE;
     cap->free_invariant_check_queues = END_INVARIANT_CHECK_QUEUE;
     cap->free_trec_chunks = END_STM_CHUNK_LIST;
@@ -264,7 +289,19 @@ initCapability( Capability *cap, nat i )
     cap->transaction_tokens = 0;
     cap->context_switch = 0;
     cap->pinned_object_block = NULL;
+    cap->pinned_object_blocks = NULL;
+
+#ifdef PROFILING
+    cap->r.rCCCS = CCS_SYSTEM;
+#else
+    cap->r.rCCCS = NULL;
+#endif
 
+    // cap->r.rCurrentTSO is charged for calls to allocate(), so we
+    // don't want it set when not running a Haskell thread.
+    cap->r.rCurrentTSO = NULL;
+
+    traceCapCreate(cap);
     traceCapsetAssignCap(CAPSET_OSPROCESS_DEFAULT, i);
     traceCapsetAssignCap(CAPSET_CLOCKDOMAIN_DEFAULT, i);
 #if defined(THREADED_RTS)
@@ -289,46 +326,71 @@ initCapabilities( void )
     traceCapsetCreate(CAPSET_CLOCKDOMAIN_DEFAULT, CapsetTypeClockdomain);
 
 #if defined(THREADED_RTS)
-    nat i;
 
 #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");
-       RtsFlags.ParFlags.nNodes = 1;
+        errorBelch("warning: multiple CPUs not supported in this build, reverting to 1");
+        RtsFlags.ParFlags.nNodes = 1;
     }
 #endif
 
+    n_capabilities = 0;
+    moreCapabilities(0, RtsFlags.ParFlags.nNodes);
     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_capabilities; i++) {
-       initCapability(&capabilities[i], i);
-    }
-
-    debugTrace(DEBUG_sched, "allocated %d capabilities", n_capabilities);
-
 #else /* !THREADED_RTS */
 
     n_capabilities = 1;
-    capabilities = &MainCapability;
+    capabilities = stgMallocBytes(sizeof(Capability*), "initCapabilities");
+    capabilities[0] = &MainCapability;
     initCapability(&MainCapability, 0);
 
 #endif
 
+    enabled_capabilities = n_capabilities;
+
     // There are no free capabilities to begin with.  We will start
     // a worker Task to each Capability, which will quickly put the
     // Capability on the free list when it finds nothing to do.
-    last_free_capability = &capabilities[0];
+    last_free_capability = capabilities[0];
+}
+
+void
+moreCapabilities (nat from USED_IF_THREADS, nat to USED_IF_THREADS)
+{
+#if defined(THREADED_RTS)
+    nat i;
+    Capability **old_capabilities = capabilities;
+
+    capabilities = stgMallocBytes(to * sizeof(Capability*), "moreCapabilities");
+
+    if (to == 1) {
+        // 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.
+        capabilities[0] = &MainCapability;
+        initCapability(&MainCapability, 0);
+    }
+    else
+    {
+        for (i = 0; i < to; i++) {
+            if (i < from) {
+                capabilities[i] = old_capabilities[i];
+            } else {
+                capabilities[i] = stgMallocBytes(sizeof(Capability),
+                                                 "moreCapabilities");
+                initCapability(capabilities[i], i);
+            }
+        }
+    }
+
+    debugTrace(DEBUG_sched, "allocated %d more capabilities", to - from);
+
+    if (old_capabilities != NULL) {
+        stgFree(old_capabilities);
+    }
+#endif
 }
 
 /* ----------------------------------------------------------------------------
@@ -336,11 +398,19 @@ initCapabilities( void )
  * soon as possible.
  * ------------------------------------------------------------------------- */
 
-void setContextSwitches(void)
+void contextSwitchAllCapabilities(void)
+{
+    nat i;
+    for (i=0; i < n_capabilities; i++) {
+        contextSwitchCapability(capabilities[i]);
+    }
+}
+
+void interruptAllCapabilities(void)
 {
     nat i;
     for (i=0; i < n_capabilities; i++) {
-        contextSwitchCapability(&capabilities[i]);
+        interruptCapability(capabilities[i]);
     }
 }
 
@@ -364,9 +434,9 @@ giveCapabilityToTask (Capability *cap USED_IF_DEBUG, Task *task)
 {
     ASSERT_LOCK_HELD(&cap->lock);
     ASSERT(task->cap == cap);
-    debugTrace(DEBUG_sched, "passing capability %d to %s %p",
+    debugTrace(DEBUG_sched, "passing capability %d to %s %#" FMT_HexWord64,
                cap->no, task->incall->tso ? "bound task" : "worker",
-               (void *)task->id);
+               serialisableTaskId(task));
     ACQUIRE_LOCK(&task->lock);
     if (task->wakeup == rtsFalse) {
         task->wakeup = rtsTrue;
@@ -389,7 +459,7 @@ giveCapabilityToTask (Capability *cap USED_IF_DEBUG, Task *task)
 
 #if defined(THREADED_RTS)
 void
-releaseCapability_ (Capability* cap, 
+releaseCapability_ (Capability* cap,
                     rtsBool always_wakeup)
 {
     Task *task;
@@ -403,56 +473,61 @@ releaseCapability_ (Capability* cap,
     // Check to see whether a worker thread can be given
     // the go-ahead to return the result of an external call..
     if (cap->returning_tasks_hd != NULL) {
-       giveCapabilityToTask(cap,cap->returning_tasks_hd);
-       // The Task pops itself from the queue (see waitForReturnCapability())
-       return;
+        giveCapabilityToTask(cap,cap->returning_tasks_hd);
+        // The Task pops itself from the queue (see waitForReturnCapability())
+        return;
     }
 
-    if (waiting_for_gc == PENDING_GC_SEQ) {
+    // If there is a pending sync, then we should just leave the
+    // Capability free.  The thread trying to sync will be about to
+    // call waitForReturnCapability().
+    if (pending_sync != 0 && pending_sync != SYNC_GC_PAR) {
       last_free_capability = cap; // needed?
-      debugTrace(DEBUG_sched, "GC pending, set capability %d free", cap->no);
+      debugTrace(DEBUG_sched, "sync pending, set capability %d free", cap->no);
       return;
-    } 
-
+    }
 
     // If the next thread on the run queue is a bound thread,
     // give this Capability to the appropriate Task.
-    if (!emptyRunQueue(cap) && cap->run_queue_hd->bound) {
-       // Make sure we're not about to try to wake ourselves up
-       // ASSERT(task != cap->run_queue_hd->bound);
+    if (!emptyRunQueue(cap) && peekRunQueue(cap)->bound) {
+        // Make sure we're not about to try to wake ourselves up
+        // ASSERT(task != cap->run_queue_hd->bound);
         // assertion is false: in schedule() we force a yield after
-       // ThreadBlocked, but the thread may be back on the run queue
-       // by now.
-       task = cap->run_queue_hd->bound->task;
-       giveCapabilityToTask(cap,task);
-       return;
+        // ThreadBlocked, but the thread may be back on the run queue
+        // by now.
+        task = peekRunQueue(cap)->bound->task;
+        giveCapabilityToTask(cap, task);
+        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
-       // shutting down, we never create a new worker.
-       if (sched_state < SCHED_SHUTTING_DOWN || !emptyRunQueue(cap)) {
-           debugTrace(DEBUG_sched,
-                      "starting new worker on capability %d", cap->no);
-           startWorkerTask(cap);
-           return;
-       }
+        // 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
+        // shutting down, we never create a new worker.
+        if (sched_state < SCHED_SHUTTING_DOWN || !emptyRunQueue(cap)) {
+            debugTrace(DEBUG_sched,
+                       "starting new worker on capability %d", cap->no);
+            startWorkerTask(cap);
+            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 (always_wakeup || 
+    if (always_wakeup ||
         !emptyRunQueue(cap) || !emptyInbox(cap) ||
-        !emptySparkPoolCap(cap) || globalWorkToDo()) {
-       if (cap->spare_workers) {
-           giveCapabilityToTask(cap,cap->spare_workers);
-           // The worker Task pops itself from the queue;
-           return;
-       }
+        (!cap->disabled && !emptySparkPoolCap(cap)) || globalWorkToDo()) {
+        if (cap->spare_workers) {
+            giveCapabilityToTask(cap, cap->spare_workers);
+            // The worker Task pops itself from the queue;
+            return;
+        }
     }
 
+#ifdef PROFILING
+    cap->r.rCCCS = CCS_IDLE;
+#endif
     last_free_capability = cap;
     debugTrace(DEBUG_sched, "freeing capability %d", cap->no);
 }
@@ -519,7 +594,7 @@ releaseCapabilityAndQueueWorker (Capability* cap USED_IF_THREADS)
 #endif
 
 /* ----------------------------------------------------------------------------
- * waitForReturnCapability( Task *task )
+ * waitForReturnCapability (Capability **pCap, Task *task)
  *
  * Purpose:  when an OS thread returns from an external call,
  * it calls waitForReturnCapability() (via Schedule.resumeThread())
@@ -541,29 +616,29 @@ waitForReturnCapability (Capability **pCap, Task *task)
     Capability *cap = *pCap;
 
     if (cap == NULL) {
-       // Try last_free_capability first
-       cap = last_free_capability;
-       if (cap->running_task) {
-           nat i;
-           // otherwise, search for a free capability
+        // Try last_free_capability first
+        cap = last_free_capability;
+        if (cap->running_task) {
+            nat i;
+            // otherwise, search for a free capability
             cap = NULL;
-           for (i = 0; i < n_capabilities; i++) {
-               if (!capabilities[i].running_task) {
-                    cap = &capabilities[i];
-                   break;
-               }
-           }
+            for (i = 0; i < n_capabilities; i++) {
+                if (!capabilities[i]->running_task) {
+                    cap = capabilities[i];
+                    break;
+                }
+            }
             if (cap == NULL) {
                 // Can't find a free one, use last_free_capability.
                 cap = last_free_capability;
             }
-       }
+        }
 
-       // record the Capability as the one this Task is now assocated with.
-       task->cap = cap;
+        // record the Capability as the one this Task is now assocated with.
+        task->cap = cap;
 
     } else {
-       ASSERT(task->cap == cap);
+        ASSERT(task->cap == cap);
     }
 
     ACQUIRE_LOCK(&cap->lock);
@@ -571,40 +646,44 @@ waitForReturnCapability (Capability **pCap, Task *task)
     debugTrace(DEBUG_sched, "returning; I want capability %d", cap->no);
 
     if (!cap->running_task) {
-       // It's free; just grab it
-       cap->running_task = task;
-       RELEASE_LOCK(&cap->lock);
+        // It's free; just grab it
+        cap->running_task = task;
+        RELEASE_LOCK(&cap->lock);
     } else {
-       newReturningTask(cap,task);
-       RELEASE_LOCK(&cap->lock);
-
-       for (;;) {
-           ACQUIRE_LOCK(&task->lock);
-           // task->lock held, cap->lock not held
-           if (!task->wakeup) waitCondition(&task->cond, &task->lock);
-           cap = task->cap;
-           task->wakeup = rtsFalse;
-           RELEASE_LOCK(&task->lock);
-
-           // now check whether we should wake up...
-           ACQUIRE_LOCK(&cap->lock);
-           if (cap->running_task == NULL) {
-               if (cap->returning_tasks_hd != task) {
-                   giveCapabilityToTask(cap,cap->returning_tasks_hd);
-                   RELEASE_LOCK(&cap->lock);
-                   continue;
-               }
-               cap->running_task = task;
-               popReturningTask(cap);
-               RELEASE_LOCK(&cap->lock);
-               break;
-           }
-           RELEASE_LOCK(&cap->lock);
-       }
+        newReturningTask(cap,task);
+        RELEASE_LOCK(&cap->lock);
+
+        for (;;) {
+            ACQUIRE_LOCK(&task->lock);
+            // task->lock held, cap->lock not held
+            if (!task->wakeup) waitCondition(&task->cond, &task->lock);
+            cap = task->cap;
+            task->wakeup = rtsFalse;
+            RELEASE_LOCK(&task->lock);
+
+            // now check whether we should wake up...
+            ACQUIRE_LOCK(&cap->lock);
+            if (cap->running_task == NULL) {
+                if (cap->returning_tasks_hd != task) {
+                    giveCapabilityToTask(cap,cap->returning_tasks_hd);
+                    RELEASE_LOCK(&cap->lock);
+                    continue;
+                }
+                cap->running_task = task;
+                popReturningTask(cap);
+                RELEASE_LOCK(&cap->lock);
+                break;
+            }
+            RELEASE_LOCK(&cap->lock);
+        }
 
     }
 
-    ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
+#ifdef PROFILING
+    cap->r.rCCCS = CCS_SYSTEM;
+#endif
+
+    ASSERT_FULL_CAPABILITY_INVARIANTS(cap, task);
 
     debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
 
@@ -617,78 +696,88 @@ waitForReturnCapability (Capability **pCap, Task *task)
  * yieldCapability
  * ------------------------------------------------------------------------- */
 
-void
-yieldCapability (Capability** pCap, Task *task)
+/* See Note [GC livelock] in Schedule.c for why we have gcAllowed
+   and return the rtsBool */
+rtsBool /* Did we GC? */
+yieldCapability (Capability** pCap, Task *task, rtsBool gcAllowed)
 {
     Capability *cap = *pCap;
 
-    if (waiting_for_gc == PENDING_GC_PAR) {
+    if ((pending_sync == SYNC_GC_PAR) && gcAllowed) {
         traceEventGcStart(cap);
         gcWorkerThread(cap);
         traceEventGcEnd(cap);
         traceSparkCounters(cap);
-        return;
+        // See Note [migrated bound threads 2]
+        if (task->cap == cap) {
+            return rtsTrue;
+        }
     }
 
-       debugTrace(DEBUG_sched, "giving up capability %d", cap->no);
+        debugTrace(DEBUG_sched, "giving up capability %d", cap->no);
 
-       // We must now release the capability and wait to be woken up
-       // again.
-       task->wakeup = rtsFalse;
-       releaseCapabilityAndQueueWorker(cap);
+        // We must now release the capability and wait to be woken up
+        // again.
+        task->wakeup = rtsFalse;
+        releaseCapabilityAndQueueWorker(cap);
 
-       for (;;) {
-           ACQUIRE_LOCK(&task->lock);
-           // task->lock held, cap->lock not held
-           if (!task->wakeup) waitCondition(&task->cond, &task->lock);
-           cap = task->cap;
-           task->wakeup = rtsFalse;
-           RELEASE_LOCK(&task->lock);
+        for (;;) {
+            ACQUIRE_LOCK(&task->lock);
+            // task->lock held, cap->lock not held
+            if (!task->wakeup) waitCondition(&task->cond, &task->lock);
+            cap = task->cap;
+            task->wakeup = rtsFalse;
+            RELEASE_LOCK(&task->lock);
 
-           debugTrace(DEBUG_sched, "woken up on capability %d", cap->no);
+            debugTrace(DEBUG_sched, "woken up on capability %d", cap->no);
 
-           ACQUIRE_LOCK(&cap->lock);
-           if (cap->running_task != NULL) {
-               debugTrace(DEBUG_sched, 
-                          "capability %d is owned by another task", cap->no);
-               RELEASE_LOCK(&cap->lock);
-               continue;
-           }
+            ACQUIRE_LOCK(&cap->lock);
+            if (cap->running_task != NULL) {
+                debugTrace(DEBUG_sched,
+                           "capability %d is owned by another task", cap->no);
+                RELEASE_LOCK(&cap->lock);
+                continue;
+            }
 
             if (task->cap != cap) {
                 // see Note [migrated bound threads]
                 debugTrace(DEBUG_sched,
                            "task has been migrated to cap %d", task->cap->no);
-               RELEASE_LOCK(&cap->lock);
-               continue;
-           }
+                RELEASE_LOCK(&cap->lock);
+                continue;
+            }
 
             if (task->incall->tso == NULL) {
-               ASSERT(cap->spare_workers != NULL);
-               // if we're not at the front of the queue, release it
-               // again.  This is unlikely to happen.
-               if (cap->spare_workers != task) {
-                   giveCapabilityToTask(cap,cap->spare_workers);
-                   RELEASE_LOCK(&cap->lock);
-                   continue;
-               }
-               cap->spare_workers = task->next;
-               task->next = NULL;
+                ASSERT(cap->spare_workers != NULL);
+                // if we're not at the front of the queue, release it
+                // again.  This is unlikely to happen.
+                if (cap->spare_workers != task) {
+                    giveCapabilityToTask(cap,cap->spare_workers);
+                    RELEASE_LOCK(&cap->lock);
+                    continue;
+                }
+                cap->spare_workers = task->next;
+                task->next = NULL;
                 cap->n_spare_workers--;
             }
-           cap->running_task = task;
-           RELEASE_LOCK(&cap->lock);
-           break;
-       }
 
-       debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
-       ASSERT(cap->running_task == task);
+            cap->running_task = task;
+            RELEASE_LOCK(&cap->lock);
+            break;
+        }
+
+        debugTrace(DEBUG_sched, "resuming capability %d", cap->no);
+        ASSERT(cap->running_task == task);
+
+#ifdef PROFILING
+        cap->r.rCCCS = CCS_SYSTEM;
+#endif
 
     *pCap = cap;
 
     ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task);
 
-    return;
+    return rtsFalse;
 }
 
 // Note [migrated bound threads]
@@ -708,10 +797,21 @@ yieldCapability (Capability** pCap, Task *task)
 //    hold Capabilty C, and task->cap == C, then task cannot be
 //    migrated under our feet.
 
+// Note [migrated bound threads 2]
+//
+// Second tricky case;
+//   - A bound Task becomes a GC thread
+//   - scheduleDoGC() migrates the thread belonging to this Task,
+//     because the Capability it is on is disabled
+//   - after GC, gcWorkerThread() returns, but now we are
+//     holding a Capability that is not the same as task->cap
+//   - Hence we must check for this case and immediately give up the
+//     cap we hold.
+
 /* ----------------------------------------------------------------------------
  * prodCapability
  *
- * If a Capability is currently idle, wake up a Task on it.  Used to 
+ * If a Capability is currently idle, wake up a Task on it.  Used to
  * get every Capability into the GC.
  * ------------------------------------------------------------------------- */
 
@@ -739,8 +839,8 @@ tryGrabCapability (Capability *cap, Task *task)
     if (cap->running_task != NULL) return rtsFalse;
     ACQUIRE_LOCK(&cap->lock);
     if (cap->running_task != NULL) {
-       RELEASE_LOCK(&cap->lock);
-       return rtsFalse;
+        RELEASE_LOCK(&cap->lock);
+        return rtsFalse;
     }
     task->cap = cap;
     cap->running_task = task;
@@ -759,7 +859,7 @@ tryGrabCapability (Capability *cap, Task *task)
  * allow the workers to stop.
  *
  * This function should be called when interrupted and
- * shutting_down_scheduler = rtsTrue, thus any worker that wakes up
+ * sched_state = SCHED_SHUTTING_DOWN, thus any worker that wakes up
  * will exit the scheduler and call taskStop(), and any bound thread
  * that wakes up will return to its caller.  Runnable threads are
  * killed.
@@ -767,7 +867,7 @@ tryGrabCapability (Capability *cap, Task *task)
  * ------------------------------------------------------------------------- */
 
 void
-shutdownCapability (Capability *cap,
+shutdownCapability (Capability *cap USED_IF_THREADS,
                     Task *task USED_IF_THREADS,
                     rtsBool safe USED_IF_THREADS)
 {
@@ -785,16 +885,16 @@ shutdownCapability (Capability *cap,
     for (i = 0; /* i < 50 */; i++) {
         ASSERT(sched_state == SCHED_SHUTTING_DOWN);
 
-       debugTrace(DEBUG_sched, 
-                  "shutting down capability %d, attempt %d", cap->no, i);
-       ACQUIRE_LOCK(&cap->lock);
-       if (cap->running_task) {
-           RELEASE_LOCK(&cap->lock);
-           debugTrace(DEBUG_sched, "not owner, yielding");
-           yieldThread();
-           continue;
-       }
-       cap->running_task = task;
+        debugTrace(DEBUG_sched,
+                   "shutting down capability %d, attempt %d", cap->no, i);
+        ACQUIRE_LOCK(&cap->lock);
+        if (cap->running_task) {
+            RELEASE_LOCK(&cap->lock);
+            debugTrace(DEBUG_sched, "not owner, yielding");
+            yieldThread();
+            continue;
+        }
+        cap->running_task = task;
 
         if (cap->spare_workers) {
             // Look for workers that have died without removing
@@ -807,8 +907,8 @@ shutdownCapability (Capability *cap,
             prev = NULL;
             for (t = cap->spare_workers; t != NULL; t = t->next) {
                 if (!osThreadIsAlive(t->id)) {
-                    debugTrace(DEBUG_sched, 
-                               "worker thread %p has died unexpectedly", (void *)t->id);
+                    debugTrace(DEBUG_sched,
+                               "worker thread %p has died unexpectedly", (void *)(size_t)t->id);
                     cap->n_spare_workers--;
                     if (!prev) {
                         cap->spare_workers = t->next;
@@ -820,14 +920,14 @@ shutdownCapability (Capability *cap,
             }
         }
 
-       if (!emptyRunQueue(cap) || cap->spare_workers) {
-           debugTrace(DEBUG_sched, 
-                      "runnable threads or workers still alive, yielding");
-           releaseCapability_(cap,rtsFalse); // this will wake up a worker
-           RELEASE_LOCK(&cap->lock);
-           yieldThread();
-           continue;
-       }
+        if (!emptyRunQueue(cap) || cap->spare_workers) {
+            debugTrace(DEBUG_sched,
+                       "runnable threads or workers still alive, yielding");
+            releaseCapability_(cap,rtsFalse); // this will wake up a worker
+            RELEASE_LOCK(&cap->lock);
+            yieldThread();
+            continue;
+        }
 
         // If "safe", then busy-wait for any threads currently doing
         // foreign calls.  If we're about to unload this DLL, for
@@ -836,10 +936,10 @@ shutdownCapability (Capability *cap,
         // We can be a bit more relaxed when this is a standalone
         // program that is about to terminate, and let safe=false.
         if (cap->suspended_ccalls && safe) {
-           debugTrace(DEBUG_sched, 
-                      "thread(s) are involved in foreign calls, yielding");
+            debugTrace(DEBUG_sched,
+                       "thread(s) are involved in foreign calls, yielding");
             cap->running_task = NULL;
-           RELEASE_LOCK(&cap->lock);
+            RELEASE_LOCK(&cap->lock);
             // The IO manager thread might have been slow to start up,
             // so the first attempt to kill it might not have
             // succeeded.  Just in case, try again - the kill message
@@ -852,24 +952,18 @@ shutdownCapability (Capability *cap,
             continue;
         }
 
-        traceEventShutdown(cap);
-       RELEASE_LOCK(&cap->lock);
-       break;
+        traceSparkCounters(cap);
+        RELEASE_LOCK(&cap->lock);
+        break;
     }
     // we now have the Capability, its run queue and spare workers
     // list are both empty.
 
     // ToDo: we can't drop this mutex, because there might still be
-    // threads performing foreign calls that will eventually try to 
+    // threads performing foreign calls that will eventually try to
     // return via resumeThread() and attempt to grab cap->lock.
     // closeMutex(&cap->lock);
-
-    traceSparkCounters(cap);
-
-#endif /* THREADED_RTS */
-
-    traceCapsetRemoveCap(CAPSET_OSPROCESS_DEFAULT, cap->no);
-    traceCapsetRemoveCap(CAPSET_CLOCKDOMAIN_DEFAULT, cap->no);
+#endif
 }
 
 void
@@ -878,11 +972,8 @@ shutdownCapabilities(Task *task, rtsBool safe)
     nat i;
     for (i=0; i < n_capabilities; i++) {
         ASSERT(task->incall->tso == NULL);
-        shutdownCapability(&capabilities[i], task, safe);
+        shutdownCapability(capabilities[i], task, safe);
     }
-    traceCapsetDelete(CAPSET_OSPROCESS_DEFAULT);
-    traceCapsetDelete(CAPSET_CLOCKDOMAIN_DEFAULT);
-
 #if defined(THREADED_RTS)
     ASSERT(checkSparkCountInvariant());
 #endif
@@ -896,6 +987,9 @@ freeCapability (Capability *cap)
 #if defined(THREADED_RTS)
     freeSparkPool(cap->sparks);
 #endif
+    traceCapsetRemoveCap(CAPSET_OSPROCESS_DEFAULT, cap->no);
+    traceCapsetRemoveCap(CAPSET_CLOCKDOMAIN_DEFAULT, cap->no);
+    traceCapDelete(cap);
 }
 
 void
@@ -904,11 +998,16 @@ freeCapabilities (void)
 #if defined(THREADED_RTS)
     nat i;
     for (i=0; i < n_capabilities; i++) {
-        freeCapability(&capabilities[i]);
+        freeCapability(capabilities[i]);
+        if (capabilities[i] != &MainCapability)
+            stgFree(capabilities[i]);
     }
 #else
     freeCapability(&MainCapability);
 #endif
+    stgFree(capabilities);
+    traceCapsetDelete(CAPSET_OSPROCESS_DEFAULT);
+    traceCapsetDelete(CAPSET_CLOCKDOMAIN_DEFAULT);
 }
 
 /* ---------------------------------------------------------------------------
@@ -953,7 +1052,7 @@ markCapabilities (evac_fn evac, void *user)
 {
     nat n;
     for (n = 0; n < n_capabilities; n++) {
-        markCapability(evac, user, &capabilities[n], rtsFalse);
+        markCapability(evac, user, capabilities[n], rtsFalse);
     }
 }
 
@@ -965,15 +1064,15 @@ rtsBool checkSparkCountInvariant (void)
     nat i;
 
     for (i = 0; i < n_capabilities; i++) {
-        sparks.created   += capabilities[i].spark_stats.created;
-        sparks.dud       += capabilities[i].spark_stats.dud;
-        sparks.overflowed+= capabilities[i].spark_stats.overflowed;
-        sparks.converted += capabilities[i].spark_stats.converted;
-        sparks.gcd       += capabilities[i].spark_stats.gcd;
-        sparks.fizzled   += capabilities[i].spark_stats.fizzled;
-        remaining        += sparkPoolSize(capabilities[i].sparks);
+        sparks.created   += capabilities[i]->spark_stats.created;
+        sparks.dud       += capabilities[i]->spark_stats.dud;
+        sparks.overflowed+= capabilities[i]->spark_stats.overflowed;
+        sparks.converted += capabilities[i]->spark_stats.converted;
+        sparks.gcd       += capabilities[i]->spark_stats.gcd;
+        sparks.fizzled   += capabilities[i]->spark_stats.fizzled;
+        remaining        += sparkPoolSize(capabilities[i]->sparks);
     }
-    
+
     /* The invariant is
      *   created = converted + remaining + gcd + fizzled
      */
@@ -987,3 +1086,15 @@ rtsBool checkSparkCountInvariant (void)
 
 }
 #endif
+
+#if !defined(mingw32_HOST_OS)
+void setIOManagerControlFd(nat cap_no USED_IF_THREADS, int fd USED_IF_THREADS) {
+#if defined(THREADED_RTS)
+    if (cap_no < n_capabilities) {
+        capabilities[cap_no]->io_manager_control_wr_fd = fd;
+    } else {
+        errorBelch("warning: setIOManagerControlFd called with illegal capability number.");
+    }
+#endif
+}
+#endif