rts/Linker.c (loadArchive):
[ghc.git] / rts / Capability.h
1 /* ---------------------------------------------------------------------------
2 *
3 * (c) The GHC Team, 2001-2006
4 *
5 * Capabilities
6 *
7 * For details on the high-level design, see
8 * http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Scheduler
9 *
10 * A Capability holds all the state an OS thread/task needs to run
11 * Haskell code: its STG registers, a pointer to its TSO, a nursery
12 * etc. During STG execution, a pointer to the Capabilitity is kept in
13 * a register (BaseReg).
14 *
15 * Only in a THREADED_RTS build will there be multiple capabilities,
16 * in the non-threaded RTS there is one global capability, called
17 * MainCapability.
18 *
19 * --------------------------------------------------------------------------*/
20
21 #ifndef CAPABILITY_H
22 #define CAPABILITY_H
23
24 #include "sm/GC.h" // for evac_fn
25 #include "Task.h"
26 #include "Sparks.h"
27
28 #include "BeginPrivate.h"
29
30 struct Capability_ {
31 // State required by the STG virtual machine when running Haskell
32 // code. During STG execution, the BaseReg register always points
33 // to the StgRegTable of the current Capability (&cap->r).
34 StgFunTable f;
35 StgRegTable r;
36
37 nat no; // capability number.
38
39 // The Task currently holding this Capability. This task has
40 // exclusive access to the contents of this Capability (apart from
41 // returning_tasks_hd/returning_tasks_tl).
42 // Locks required: cap->lock.
43 Task *running_task;
44
45 // true if this Capability is running Haskell code, used for
46 // catching unsafe call-ins.
47 rtsBool in_haskell;
48
49 // The run queue. The Task owning this Capability has exclusive
50 // access to its run queue, so can wake up threads without
51 // taking a lock, and the common path through the scheduler is
52 // also lock-free.
53 StgTSO *run_queue_hd;
54 StgTSO *run_queue_tl;
55
56 // Tasks currently making safe foreign calls. Doubly-linked.
57 // When returning, a task first acquires the Capability before
58 // removing itself from this list, so that the GC can find all
59 // the suspended TSOs easily. Hence, when migrating a Task from
60 // the returning_tasks list, we must also migrate its entry from
61 // this list.
62 InCall *suspended_ccalls;
63
64 // One mutable list per generation, so we don't need to take any
65 // locks when updating an old-generation thunk. This also lets us
66 // keep track of which closures this CPU has been mutating, so we
67 // can traverse them using the right thread during GC and avoid
68 // unnecessarily moving the data from one cache to another.
69 bdescr **mut_lists;
70 bdescr **saved_mut_lists; // tmp use during GC
71
72 // block for allocating pinned objects into
73 bdescr *pinned_object_block;
74
75 // Context switch flag. We used to have one global flag, now one
76 // per capability. Locks required : none (conflicts are harmless)
77 int context_switch;
78
79 #if defined(THREADED_RTS)
80 // Worker Tasks waiting in the wings. Singly-linked.
81 Task *spare_workers;
82 nat n_spare_workers; // count of above
83
84 // This lock protects running_task, returning_tasks_{hd,tl}, wakeup_queue.
85 Mutex lock;
86
87 // Tasks waiting to return from a foreign call, or waiting to make
88 // a new call-in using this Capability (NULL if empty).
89 // NB. this field needs to be modified by tasks other than the
90 // running_task, so it requires cap->lock to modify. A task can
91 // check whether it is NULL without taking the lock, however.
92 Task *returning_tasks_hd; // Singly-linked, with head/tail
93 Task *returning_tasks_tl;
94
95 // Messages, or END_TSO_QUEUE.
96 Message *inbox;
97
98 SparkPool *sparks;
99
100 // Stats on spark creation/conversion
101 nat sparks_created;
102 nat sparks_converted;
103 nat sparks_pruned;
104 #endif
105
106 // Per-capability STM-related data
107 StgTVarWatchQueue *free_tvar_watch_queues;
108 StgInvariantCheckQueue *free_invariant_check_queues;
109 StgTRecChunk *free_trec_chunks;
110 StgTRecHeader *free_trec_headers;
111 nat transaction_tokens;
112 } // typedef Capability is defined in RtsAPI.h
113 // Capabilities are stored in an array, so make sure that adjacent
114 // Capabilities don't share any cache-lines:
115 #ifndef mingw32_HOST_OS
116 ATTRIBUTE_ALIGNED(64)
117 #endif
118 ;
119
120
121 #if defined(THREADED_RTS)
122 #define ASSERT_TASK_ID(task) ASSERT(task->id == osThreadId())
123 #else
124 #define ASSERT_TASK_ID(task) /*empty*/
125 #endif
126
127 // These properties should be true when a Task is holding a Capability
128 #define ASSERT_FULL_CAPABILITY_INVARIANTS(cap,task) \
129 ASSERT(cap->running_task != NULL && cap->running_task == task); \
130 ASSERT(task->cap == cap); \
131 ASSERT_PARTIAL_CAPABILITY_INVARIANTS(cap,task)
132
133 // Sometimes a Task holds a Capability, but the Task is not associated
134 // with that Capability (ie. task->cap != cap). This happens when
135 // (a) a Task holds multiple Capabilities, and (b) when the current
136 // Task is bound, its thread has just blocked, and it may have been
137 // moved to another Capability.
138 #define ASSERT_PARTIAL_CAPABILITY_INVARIANTS(cap,task) \
139 ASSERT(cap->run_queue_hd == END_TSO_QUEUE ? \
140 cap->run_queue_tl == END_TSO_QUEUE : 1); \
141 ASSERT(myTask() == task); \
142 ASSERT_TASK_ID(task);
143
144 // Converts a *StgRegTable into a *Capability.
145 //
146 INLINE_HEADER Capability *
147 regTableToCapability (StgRegTable *reg)
148 {
149 return (Capability *)((void *)((unsigned char*)reg - STG_FIELD_OFFSET(Capability,r)));
150 }
151
152 // Initialise the available capabilities.
153 //
154 void initCapabilities (void);
155
156 // Release a capability. This is called by a Task that is exiting
157 // Haskell to make a foreign call, or in various other cases when we
158 // want to relinquish a Capability that we currently hold.
159 //
160 // ASSUMES: cap->running_task is the current Task.
161 //
162 #if defined(THREADED_RTS)
163 void releaseCapability (Capability* cap);
164 void releaseAndWakeupCapability (Capability* cap);
165 void releaseCapability_ (Capability* cap, rtsBool always_wakeup);
166 // assumes cap->lock is held
167 #else
168 // releaseCapability() is empty in non-threaded RTS
169 INLINE_HEADER void releaseCapability (Capability* cap STG_UNUSED) {};
170 INLINE_HEADER void releaseAndWakeupCapability (Capability* cap STG_UNUSED) {};
171 INLINE_HEADER void releaseCapability_ (Capability* cap STG_UNUSED,
172 rtsBool always_wakeup STG_UNUSED) {};
173 #endif
174
175 // declared in includes/rts/Threads.h:
176 // extern Capability MainCapability;
177
178 // declared in includes/rts/Threads.h:
179 // extern nat n_capabilities;
180
181 // Array of all the capabilities
182 //
183 extern Capability *capabilities;
184
185 // The Capability that was last free. Used as a good guess for where
186 // to assign new threads.
187 //
188 extern Capability *last_free_capability;
189
190 // GC indicator, in scope for the scheduler
191 #define PENDING_GC_SEQ 1
192 #define PENDING_GC_PAR 2
193 extern volatile StgWord waiting_for_gc;
194
195 // Acquires a capability at a return point. If *cap is non-NULL, then
196 // this is taken as a preference for the Capability we wish to
197 // acquire.
198 //
199 // OS threads waiting in this function get priority over those waiting
200 // in waitForCapability().
201 //
202 // On return, *cap is non-NULL, and points to the Capability acquired.
203 //
204 void waitForReturnCapability (Capability **cap/*in/out*/, Task *task);
205
206 EXTERN_INLINE void recordMutableCap (StgClosure *p, Capability *cap, nat gen);
207
208 EXTERN_INLINE void recordClosureMutated (Capability *cap, StgClosure *p);
209
210 #if defined(THREADED_RTS)
211
212 // Gives up the current capability IFF there is a higher-priority
213 // thread waiting for it. This happens in one of two ways:
214 //
215 // (a) we are passing the capability to another OS thread, so
216 // that it can run a bound Haskell thread, or
217 //
218 // (b) there is an OS thread waiting to return from a foreign call
219 //
220 // On return: *pCap is NULL if the capability was released. The
221 // current task should then re-acquire it using waitForCapability().
222 //
223 void yieldCapability (Capability** pCap, Task *task);
224
225 // Acquires a capability for doing some work.
226 //
227 // On return: pCap points to the capability.
228 //
229 void waitForCapability (Task *task, Mutex *mutex, Capability **pCap);
230
231 // Wakes up a worker thread on just one Capability, used when we
232 // need to service some global event.
233 //
234 void prodOneCapability (void);
235 void prodCapability (Capability *cap, Task *task);
236
237 // Similar to prodOneCapability(), but prods all of them.
238 //
239 void prodAllCapabilities (void);
240
241 // Waits for a capability to drain of runnable threads and workers,
242 // and then acquires it. Used at shutdown time.
243 //
244 void shutdownCapability (Capability *cap, Task *task, rtsBool wait_foreign);
245
246 // Attempt to gain control of a Capability if it is free.
247 //
248 rtsBool tryGrabCapability (Capability *cap, Task *task);
249
250 // Try to find a spark to run
251 //
252 StgClosure *findSpark (Capability *cap);
253
254 // True if any capabilities have sparks
255 //
256 rtsBool anySparks (void);
257
258 INLINE_HEADER rtsBool emptySparkPoolCap (Capability *cap);
259 INLINE_HEADER nat sparkPoolSizeCap (Capability *cap);
260 INLINE_HEADER void discardSparksCap (Capability *cap);
261
262 #else // !THREADED_RTS
263
264 // Grab a capability. (Only in the non-threaded RTS; in the threaded
265 // RTS one of the waitFor*Capability() functions must be used).
266 //
267 extern void grabCapability (Capability **pCap);
268
269 #endif /* !THREADED_RTS */
270
271 // cause all capabilities to context switch as soon as possible.
272 void setContextSwitches(void);
273 INLINE_HEADER void contextSwitchCapability(Capability *cap);
274
275 // Free all capabilities
276 void freeCapabilities (void);
277
278 // For the GC:
279 void markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta,
280 rtsBool no_mark_sparks);
281 void markCapabilities (evac_fn evac, void *user);
282 void traverseSparkQueues (evac_fn evac, void *user);
283
284 /* -----------------------------------------------------------------------------
285 Messages
286 -------------------------------------------------------------------------- */
287
288 #ifdef THREADED_RTS
289
290 INLINE_HEADER rtsBool emptyInbox(Capability *cap);;
291
292 #endif // THREADED_RTS
293
294 /* -----------------------------------------------------------------------------
295 * INLINE functions... private below here
296 * -------------------------------------------------------------------------- */
297
298 EXTERN_INLINE void
299 recordMutableCap (StgClosure *p, Capability *cap, nat gen)
300 {
301 bdescr *bd;
302
303 // We must own this Capability in order to modify its mutable list.
304 // ASSERT(cap->running_task == myTask());
305 // NO: assertion is violated by performPendingThrowTos()
306 bd = cap->mut_lists[gen];
307 if (bd->free >= bd->start + BLOCK_SIZE_W) {
308 bdescr *new_bd;
309 new_bd = allocBlock_lock();
310 new_bd->link = bd;
311 bd = new_bd;
312 cap->mut_lists[gen] = bd;
313 }
314 *bd->free++ = (StgWord)p;
315 }
316
317 EXTERN_INLINE void
318 recordClosureMutated (Capability *cap, StgClosure *p)
319 {
320 bdescr *bd;
321 bd = Bdescr((StgPtr)p);
322 if (bd->gen_no != 0) recordMutableCap(p,cap,bd->gen_no);
323 }
324
325
326 #if defined(THREADED_RTS)
327 INLINE_HEADER rtsBool
328 emptySparkPoolCap (Capability *cap)
329 { return looksEmpty(cap->sparks); }
330
331 INLINE_HEADER nat
332 sparkPoolSizeCap (Capability *cap)
333 { return sparkPoolSize(cap->sparks); }
334
335 INLINE_HEADER void
336 discardSparksCap (Capability *cap)
337 { return discardSparks(cap->sparks); }
338 #endif
339
340 INLINE_HEADER void
341 contextSwitchCapability (Capability *cap)
342 {
343 // setting HpLim to NULL ensures that the next heap check will
344 // fail, and the thread will return to the scheduler.
345 cap->r.rHpLim = NULL;
346 // But just in case it didn't work (the target thread might be
347 // modifying HpLim at the same time), we set the end-of-block
348 // context-switch flag too:
349 cap->context_switch = 1;
350 }
351
352 #ifdef THREADED_RTS
353
354 INLINE_HEADER rtsBool emptyInbox(Capability *cap)
355 {
356 return (cap->inbox == (Message*)END_TSO_QUEUE);
357 }
358
359 #endif
360
361 #include "EndPrivate.h"
362
363 #endif /* CAPABILITY_H */