count "dud" sparks (expressions that were already evaluated when sparked)
[ghc.git] / rts / Capability.c
index c27733f..9f7d152 100644 (file)
 
 #include "PosixSource.h"
 #include "Rts.h"
-#include "RtsUtils.h"
-#include "RtsFlags.h"
-#include "STM.h"
-#include "OSThreads.h"
+
 #include "Capability.h"
 #include "Schedule.h"
 #include "Sparks.h"
 #include "Trace.h"
-#include "GC.h"
+#include "sm/GC.h" // for gcWorkerThread()
+#include "STM.h"
+#include "RtsUtils.h"
 
 // one global capability, this is the Capability for non-threaded
 // builds, and for +RTS -N1
 Capability MainCapability;
 
-nat n_capabilities;
+nat n_capabilities = 0;
 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.
 // Maintaining a global free list of Capabilities would require global
 // locking, so we don't do that.
-Capability *last_free_capability;
+Capability *last_free_capability = NULL;
 
 /* GC indicator, in scope for the scheduler, init'ed to false */
 volatile StgWord waiting_for_gc = 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
+ * stgAllocForGMP() function (which gets called by gmp functions).
+ * */
+Capability * rts_unsafeGetMyCapability (void)
+{
+#if defined(THREADED_RTS)
+  return myTask()->cap;
+#else
+  return &MainCapability;
+#endif
+}
+
 #if defined(THREADED_RTS)
 STATIC_INLINE rtsBool
 globalWorkToDo (void)
 {
-    return blackholes_need_checking
-       || sched_state >= SCHED_INTERRUPTING
-       ;
+    return sched_state >= SCHED_INTERRUPTING
+        || recent_activity == ACTIVITY_INACTIVE; // need to check for deadlock
 }
 #endif
 
@@ -63,37 +76,40 @@ findSpark (Capability *cap)
   rtsBool retry;
   nat i = 0;
 
-  if (!emptyRunQueue(cap)) {
+  if (!emptyRunQueue(cap) || cap->returning_tasks_hd != NULL) {
       // If there are other threads, don't try to run any new
       // sparks: sparks might be speculative, we don't want to take
       // resources away from the main computation.
       return 0;
   }
 
-  // first try to get a spark from our own pool.
-  // We should be using reclaimSpark(), because it works without
-  // needing any atomic instructions:
-  //   spark = reclaimSpark(cap->sparks);
-  // However, measurements show that this makes at least one benchmark
-  // slower (prsa) and doesn't affect the others.
-  spark = tryStealSpark(cap);
-  if (spark != NULL) {
-      cap->sparks_converted++;
+  do {
+      retry = rtsFalse;
 
-      // Post event for running a spark from capability's own pool.
-      postEvent(cap, EVENT_RUN_SPARK, cap->r.rCurrentTSO->id, 0);
+      // first try to get a spark from our own pool.
+      // We should be using reclaimSpark(), because it works without
+      // needing any atomic instructions:
+      //   spark = reclaimSpark(cap->sparks);
+      // However, measurements show that this makes at least one benchmark
+      // slower (prsa) and doesn't affect the others.
+      spark = tryStealSpark(cap);
+      if (spark != NULL) {
+          cap->sparks_converted++;
 
-      return spark;
-  }
+          // Post event for running a spark from capability's own pool.
+          traceEventRunSpark(cap, cap->r.rCurrentTSO);
 
-  if (n_capabilities == 1) { return NULL; } // makes no sense...
+          return spark;
+      }
+      if (!emptySparkPoolCap(cap)) {
+          retry = rtsTrue;
+      }
 
-  debugTrace(DEBUG_sched,
-            "cap %d: Trying to steal work from other capabilities", 
-            cap->no);
+      if (n_capabilities == 1) { return NULL; } // makes no sense...
 
-  do {
-      retry = rtsFalse;
+      debugTrace(DEBUG_sched,
+                 "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.  */
@@ -113,14 +129,9 @@ findSpark (Capability *cap)
           }
 
           if (spark != NULL) {
-              debugTrace(DEBUG_sched,
-                "cap %d: Stole a spark from capability %d",
-                         cap->no, robbed->no);
               cap->sparks_converted++;
 
-              postEvent(cap, EVENT_STEAL_SPARK, 
-                        cap->r.rCurrentTSO->id, robbed->no);
-                        
+              traceEventStealSpark(cap, cap->r.rCurrentTSO, robbed->no);
               
               return spark;
           }
@@ -161,10 +172,10 @@ STATIC_INLINE void
 newReturningTask (Capability *cap, Task *task)
 {
     ASSERT_LOCK_HELD(&cap->lock);
-    ASSERT(task->return_link == NULL);
+    ASSERT(task->next == NULL);
     if (cap->returning_tasks_hd) {
-       ASSERT(cap->returning_tasks_tl->return_link == NULL);
-       cap->returning_tasks_tl->return_link = task;
+       ASSERT(cap->returning_tasks_tl->next == NULL);
+       cap->returning_tasks_tl->next = task;
     } else {
        cap->returning_tasks_hd = task;
     }
@@ -178,11 +189,11 @@ popReturningTask (Capability *cap)
     Task *task;
     task = cap->returning_tasks_hd;
     ASSERT(task);
-    cap->returning_tasks_hd = task->return_link;
+    cap->returning_tasks_hd = task->next;
     if (!cap->returning_tasks_hd) {
        cap->returning_tasks_tl = NULL;
     }
-    task->return_link = NULL;
+    task->next = NULL;
     return task;
 }
 #endif
@@ -200,7 +211,6 @@ initCapability( Capability *cap, nat i )
 
     cap->no = i;
     cap->in_haskell        = rtsFalse;
-    cap->in_gc             = rtsFalse;
 
     cap->run_queue_hd      = END_TSO_QUEUE;
     cap->run_queue_tl      = END_TSO_QUEUE;
@@ -209,19 +219,20 @@ initCapability( Capability *cap, nat i )
     initMutex(&cap->lock);
     cap->running_task      = NULL; // indicates cap is free
     cap->spare_workers     = NULL;
-    cap->suspended_ccalling_tasks = NULL;
+    cap->n_spare_workers   = 0;
+    cap->suspended_ccalls  = NULL;
     cap->returning_tasks_hd = NULL;
     cap->returning_tasks_tl = NULL;
-    cap->wakeup_queue_hd    = END_TSO_QUEUE;
-    cap->wakeup_queue_tl    = END_TSO_QUEUE;
+    cap->inbox              = (Message*)END_TSO_QUEUE;
     cap->sparks_created     = 0;
+    cap->sparks_dud         = 0;
     cap->sparks_converted   = 0;
     cap->sparks_pruned      = 0;
 #endif
 
     cap->f.stgEagerBlackholeInfo = (W_)&__stg_EAGER_BLACKHOLE_info;
-    cap->f.stgGCEnter1     = (F_)__stg_gc_enter_1;
-    cap->f.stgGCFun        = (F_)__stg_gc_fun;
+    cap->f.stgGCEnter1     = (StgFunPtr)__stg_gc_enter_1;
+    cap->f.stgGCFun        = (StgFunPtr)__stg_gc_fun;
 
     cap->mut_lists  = stgMallocBytes(sizeof(bdescr *) *
                                     RtsFlags.GcFlags.generations,
@@ -240,6 +251,7 @@ initCapability( Capability *cap, nat i )
     cap->free_trec_headers = NO_TREC;
     cap->transaction_tokens = 0;
     cap->context_switch = 0;
+    cap->pinned_object_block = NULL;
 }
 
 /* ---------------------------------------------------------------------------
@@ -330,7 +342,7 @@ 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",
-               cap->no, task->tso ? "bound task" : "worker",
+               cap->no, task->incall->tso ? "bound task" : "worker",
                (void *)task->id);
     ACQUIRE_LOCK(&task->lock);
     task->wakeup = rtsTrue;
@@ -382,8 +394,11 @@ releaseCapability_ (Capability* cap,
     // 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);
-       task = cap->run_queue_hd->bound;
+       // 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;
     }
@@ -396,7 +411,7 @@ releaseCapability_ (Capability* cap,
        if (sched_state < SCHED_SHUTTING_DOWN || !emptyRunQueue(cap)) {
            debugTrace(DEBUG_sched,
                       "starting new worker on capability %d", cap->no);
-           startWorkerTask(cap, workerStart);
+           startWorkerTask(cap);
            return;
        }
     }
@@ -404,7 +419,7 @@ releaseCapability_ (Capability* cap,
     // 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 || 
-        !emptyRunQueue(cap) || !emptyWakeupQueue(cap) ||
+        !emptyRunQueue(cap) || !emptyInbox(cap) ||
         !emptySparkPoolCap(cap) || globalWorkToDo()) {
        if (cap->spare_workers) {
            giveCapabilityToTask(cap,cap->spare_workers);
@@ -442,16 +457,33 @@ releaseCapabilityAndQueueWorker (Capability* cap USED_IF_THREADS)
 
     task = cap->running_task;
 
+    // If the Task is stopped, we shouldn't be yielding, we should
+    // be just exiting.
+    ASSERT(!task->stopped);
+
     // If the current task is a worker, save it on the spare_workers
     // list of this Capability.  A worker can mark itself as stopped,
     // in which case it is not replaced on the spare_worker queue.
     // This happens when the system is shutting down (see
     // Schedule.c:workerStart()).
-    // Also, be careful to check that this task hasn't just exited
-    // Haskell to do a foreign call (task->suspended_tso).
-    if (!isBoundTask(task) && !task->stopped && !task->suspended_tso) {
-       task->next = cap->spare_workers;
-       cap->spare_workers = task;
+    if (!isBoundTask(task))
+    {
+        if (cap->n_spare_workers < MAX_SPARE_WORKERS)
+        {
+            task->next = cap->spare_workers;
+            cap->spare_workers = task;
+            cap->n_spare_workers++;
+        }
+        else
+        {
+            debugTrace(DEBUG_sched, "%d spare workers already, exiting",
+                       cap->n_spare_workers);
+            releaseCapability_(cap,rtsFalse);
+            // hold the lock until after workerTaskStop; c.f. scheduleWorker()
+            workerTaskStop(task);
+            RELEASE_LOCK(&cap->lock);
+            shutdownThread();
+        }
     }
     // Bound tasks just float around attached to their TSOs.
 
@@ -486,7 +518,7 @@ waitForReturnCapability (Capability **pCap, Task *task)
     if (cap == NULL) {
        // Try last_free_capability first
        cap = last_free_capability;
-       if (!cap->running_task) {
+       if (cap->running_task) {
            nat i;
            // otherwise, search for a free capability
             cap = NULL;
@@ -566,10 +598,9 @@ yieldCapability (Capability** pCap, Task *task)
     Capability *cap = *pCap;
 
     if (waiting_for_gc == PENDING_GC_PAR) {
-       debugTrace(DEBUG_sched, "capability %d: becoming a GC thread", cap->no);
-        postEvent(cap, EVENT_GC_START, 0, 0);
+        traceEventGcStart(cap);
         gcWorkerThread(cap);
-        postEvent(cap, EVENT_GC_END, 0, 0);
+        traceEventGcEnd(cap);
         return;
     }
 
@@ -598,7 +629,7 @@ yieldCapability (Capability** pCap, Task *task)
                continue;
            }
 
-           if (task->tso == NULL) {
+           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.
@@ -609,7 +640,8 @@ yieldCapability (Capability** pCap, Task *task)
                }
                cap->spare_workers = task->next;
                task->next = NULL;
-           }
+                cap->n_spare_workers--;
+            }
            cap->running_task = task;
            RELEASE_LOCK(&cap->lock);
            break;
@@ -626,50 +658,6 @@ yieldCapability (Capability** pCap, Task *task)
 }
 
 /* ----------------------------------------------------------------------------
- * Wake up a thread on a Capability.
- *
- * This is used when the current Task is running on a Capability and
- * wishes to wake up a thread on a different Capability.
- * ------------------------------------------------------------------------- */
-
-void
-wakeupThreadOnCapability (Capability *my_cap, 
-                          Capability *other_cap, 
-                          StgTSO *tso)
-{
-    ACQUIRE_LOCK(&other_cap->lock);
-
-    // ASSUMES: cap->lock is held (asserted in wakeupThreadOnCapability)
-    if (tso->bound) {
-       ASSERT(tso->bound->cap == tso->cap);
-       tso->bound->cap = other_cap;
-    }
-    tso->cap = other_cap;
-
-    ASSERT(tso->bound ? tso->bound->cap == other_cap : 1);
-
-    if (other_cap->running_task == NULL) {
-       // nobody is running this Capability, we can add our thread
-       // directly onto the run queue and start up a Task to run it.
-
-       other_cap->running_task = myTask(); 
-            // precond for releaseCapability_() and appendToRunQueue()
-
-       appendToRunQueue(other_cap,tso);
-
-       releaseCapability_(other_cap,rtsFalse);
-    } else {
-       appendToWakeupQueue(my_cap,other_cap,tso);
-        other_cap->context_switch = 1;
-       // someone is running on this Capability, so it cannot be
-       // freed without first checking the wakeup queue (see
-       // releaseCapability_).
-    }
-
-    RELEASE_LOCK(&other_cap->lock);
-}
-
-/* ----------------------------------------------------------------------------
  * prodCapability
  *
  * If a Capability is currently idle, wake up a Task on it.  Used to 
@@ -742,12 +730,13 @@ shutdownCapability (Capability *cap, Task *task, rtsBool safe)
                 if (!osThreadIsAlive(t->id)) {
                     debugTrace(DEBUG_sched, 
                                "worker thread %p has died unexpectedly", (void *)t->id);
-                        if (!prev) {
-                            cap->spare_workers = t->next;
-                        } else {
-                            prev->next = t->next;
-                        }
-                        prev = t;
+                    cap->n_spare_workers--;
+                    if (!prev) {
+                        cap->spare_workers = t->next;
+                    } else {
+                        prev->next = t->next;
+                    }
+                    prev = t;
                 }
             }
         }
@@ -767,17 +756,24 @@ shutdownCapability (Capability *cap, Task *task, rtsBool safe)
         // that will try to return to code that has been unloaded.
         // 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_ccalling_tasks && safe) {
+        if (cap->suspended_ccalls && safe) {
            debugTrace(DEBUG_sched, 
                       "thread(s) are involved in foreign calls, yielding");
             cap->running_task = NULL;
            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
+            // will only be sent once.
+            //
+            // To reproduce this deadlock: run ffi002(threaded1)
+            // repeatedly on a loaded machine.
+            ioManagerDie();
             yieldThread();
             continue;
         }
-            
-        postEvent(cap, EVENT_SHUTDOWN, 0, 0);
-       debugTrace(DEBUG_sched, "capability %d is stopped.", cap->no);
+
+        traceEventShutdown(cap);
        RELEASE_LOCK(&cap->lock);
        break;
     }
@@ -819,6 +815,7 @@ static void
 freeCapability (Capability *cap)
 {
     stgFree(cap->mut_lists);
+    stgFree(cap->saved_mut_lists);
 #if defined(THREADED_RTS)
     freeSparkPool(cap->sparks);
 #endif
@@ -845,11 +842,11 @@ freeCapabilities (void)
 
 void
 markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta, 
-                      rtsBool prune_sparks USED_IF_THREADS)
+                      rtsBool no_mark_sparks USED_IF_THREADS)
 {
     nat i;
     Capability *cap;
-    Task *task;
+    InCall *incall;
 
     // Each GC thread is responsible for following roots from the
     // Capability of the same number.  There will usually be the same
@@ -861,20 +858,15 @@ markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta,
        evac(user, (StgClosure **)(void *)&cap->run_queue_hd);
        evac(user, (StgClosure **)(void *)&cap->run_queue_tl);
 #if defined(THREADED_RTS)
-       evac(user, (StgClosure **)(void *)&cap->wakeup_queue_hd);
-       evac(user, (StgClosure **)(void *)&cap->wakeup_queue_tl);
+        evac(user, (StgClosure **)(void *)&cap->inbox);
 #endif
-       for (task = cap->suspended_ccalling_tasks; task != NULL; 
-            task=task->next) {
-           debugTrace(DEBUG_sched,
-                      "evac'ing suspended TSO %lu", (unsigned long)task->suspended_tso->id);
-           evac(user, (StgClosure **)(void *)&task->suspended_tso);
+       for (incall = cap->suspended_ccalls; incall != NULL; 
+            incall=incall->next) {
+           evac(user, (StgClosure **)(void *)&incall->suspended_tso);
        }
 
 #if defined(THREADED_RTS)
-        if (prune_sparks) {
-            pruneSparkQueue (evac, user, cap);
-        } else {
+        if (!no_mark_sparks) {
             traverseSparkQueue (evac, user, cap);
         }
 #endif
@@ -892,3 +884,8 @@ markCapabilities (evac_fn evac, void *user)
 {
     markSomeCapabilities(evac, user, 0, 1, rtsFalse);
 }
+
+/* -----------------------------------------------------------------------------
+   Messages
+   -------------------------------------------------------------------------- */
+