/* ---------------------------------------------------------------------------
*
- * (c) The GHC Team, 2001
+ * (c) The GHC Team, 2001-2003
*
* Capabilities
*
* (the main, and only, consumer of this interface is the scheduler).
*
* --------------------------------------------------------------------------*/
-#ifndef __CAPABILITY_H__
-#define __CAPABILITY_H__
+
+#ifndef CAPABILITY_H
+#define CAPABILITY_H
+
#include "RtsFlags.h"
-/* ToDo: assume that RtsFlags.h has been included at usage sites of Capability.h? */
+#include "Task.h"
-#if !defined(SMP)
-extern Capability MainCapability;
-#endif
+struct Capability_ {
+ // State required by the STG virtual machine when running Haskell
+ // code. During STG execution, the BaseReg register always points
+ // to the StgRegTable of the current Capability (&cap->r).
+ StgFunTable f;
+ StgRegTable r;
-extern void initCapabilities(void);
-extern void grabCapability(Capability** pCap);
-extern void releaseCapability(Capability* cap);
+ nat no; // capability number.
-extern nat rts_n_free_capabilities;
-#if defined(RTS_SUPPORTS_THREADS)
-/* number of worker threads waiting for a return capability
- */
-extern nat rts_n_waiting_workers;
+ // The Task currently holding this Capability. This task has
+ // exclusive access to the contents of this Capability (apart from
+ // returning_tasks_hd/returning_tasks_tl).
+ // Locks required: cap->lock.
+ Task *running_task;
-extern void grabReturnCapability(Mutex* pMutex, Capability** pCap);
-extern void yieldToReturningWorker(Mutex* pMutex, Capability** pCap, Condition *pThreadCond);
-extern void waitForWorkCapability(Mutex* pMutex, Capability** pCap, Condition *pThreadCond);
-extern void passCapability(Mutex* pMutex, Capability* cap, Condition *pTargetThreadCond);
-extern void passCapabilityToWorker(Mutex* pMutex, Capability* cap);
+ // true if this Capability is running Haskell code, used for
+ // catching unsafe call-ins.
+ rtsBool in_haskell;
-static inline rtsBool needToYieldToReturningWorker(void)
-{
- return rts_n_waiting_workers > 0;
-}
+ // The run queue. The Task owning this Capability has exclusive
+ // access to its run queue, so can wake up threads without
+ // taking a lock, and the common path through the scheduler is
+ // also lock-free.
+ StgTSO *run_queue_hd;
+ StgTSO *run_queue_tl;
-static inline nat getFreeCapabilities (void)
-{
- return rts_n_free_capabilities;
-}
+ // Tasks currently making safe foreign calls. Doubly-linked.
+ // When returning, a task first acquires the Capability before
+ // removing itself from this list, so that the GC can find all
+ // the suspended TSOs easily. Hence, when migrating a Task from
+ // the returning_tasks list, we must also migrate its entry from
+ // this list.
+ Task *suspended_ccalling_tasks;
-static inline rtsBool noCapabilities (void)
-{
- return (rts_n_free_capabilities == 0);
-}
+#if defined(THREADED_RTS)
+ struct Capability_ *next;
+ struct Capability_ *prev;
+
+ // Worker Tasks waiting in the wings. Singly-linked.
+ Task *spare_workers;
-static inline rtsBool allFreeCapabilities (void)
+ // This lock protects running_task and returning_tasks_{hd,tl}.
+ Mutex lock;
+
+ // Tasks waiting to return from a foreign call, or waiting to make
+ // a new call-in using this Capability (NULL if empty).
+ // NB. this field needs to be modified by tasks other than the
+ // running_task, so it requires cap->lock to modify. A task can
+ // check whether it is NULL without taking the lock, however.
+ Task *returning_tasks_hd; // Singly-linked, with head/tail
+ Task *returning_tasks_tl;
+#endif
+}; // typedef Capability, defined in RtsAPI.h
+
+// Converts a *StgRegTable into a *Capability.
+//
+INLINE_HEADER Capability *
+regTableToCapability (StgRegTable *reg)
{
-# if defined(SMP)
- return (rts_n_free_capabilities == RtsFlags.ParFlags.nNodes);
-# else
- return (rts_n_free_capabilities == 1);
-# endif
+ return (Capability *)((void *)((unsigned char*)reg - sizeof(StgFunTable)));
}
-#endif /* RTS_SUPPORTS_THREADS */
+// Initialise the available capabilities.
+//
+void initCapabilities (void);
+
+// Release a capability. This is called by a Task that is exiting
+// Haskell to make a foreign call, or in various other cases when we
+// want to relinquish a Capability that we currently hold.
+//
+// ASSUMES: cap->running_task is the current Task.
+//
+#if defined(THREADED_RTS)
+void releaseCapability (Capability* cap);
+void releaseCapability_ (Capability* cap); // assumes cap->lock is held
+#else
+// releaseCapability() is empty in non-threaded RTS
+INLINE_HEADER void releaseCapability (Capability* cap STG_UNUSED) {};
+INLINE_HEADER void releaseCapability_ (Capability* cap STG_UNUSED) {};
+#endif
+
+#if !IN_STG_CODE && !defined(SMP)
+// for non-SMP, we have one global capability
+extern Capability MainCapability;
+#endif
+
+// Array of all the capabilities
+//
+extern nat n_capabilities;
+extern Capability *capabilities;
+
+// The Capability that was last free. Used as a good guess for where
+// to assign new threads.
+//
+extern Capability *last_free_capability;
+
+// Acquires a capability at a return point. If *cap is non-NULL, then
+// this is taken as a preference for the Capability we wish to
+// acquire.
+//
+// OS threads waiting in this function get priority over those waiting
+// in waitForCapability().
+//
+// On return, *cap is non-NULL, and points to the Capability acquired.
+//
+void waitForReturnCapability (Capability **cap/*in/out*/, Task *task);
+
+#if defined(THREADED_RTS)
+
+// Gives up the current capability IFF there is a higher-priority
+// thread waiting for it. This happens in one of two ways:
+//
+// (a) we are passing the capability to another OS thread, so
+// that it can run a bound Haskell thread, or
+//
+// (b) there is an OS thread waiting to return from a foreign call
+//
+// On return: *pCap is NULL if the capability was released. The
+// current task should then re-acquire it using waitForCapability().
+//
+void yieldCapability (Capability** pCap, Task *task);
+
+// Acquires a capability for doing some work.
+//
+// On return: pCap points to the capability.
+//
+void waitForCapability (Task *task, Mutex *mutex, Capability **pCap);
+
+// Wakes up a worker thread on just one Capability, used when we
+// need to service some global event.
+//
+void prodOneCapability (void);
+
+// Similar to prodOneCapability(), but prods all of them.
+//
+void prodAllCapabilities (void);
+
+// Waits for a capability to drain of runnable threads and workers,
+// and then acquires it. Used at shutdown time.
+//
+void shutdownCapability (Capability *cap, Task *task);
+
+#else // !THREADED_RTS
+
+// Grab a capability. (Only in the non-threaded RTS; in the threaded
+// RTS one of the waitFor*Capability() functions must be used).
+//
+extern void grabCapability (Capability **pCap);
+
+#endif /* !THREADED_RTS */
-#endif /* __CAPABILITY_H__ */
+#endif /* CAPABILITY_H */
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