1 /* -----------------------------------------------------------------------------
2 * $Id: TSO.h,v 1.9 1999/12/01 14:34:49 simonmar Exp $
4 * (c) The GHC Team, 1998-1999
6 * The definitions for Thread State Objects.
8 * ---------------------------------------------------------------------------*/
13 #if defined(PROFILING)
15 CostCentreStack *CCCS; /* thread's current CCS */
17 #else /* !PROFILING */
20 #endif /* PROFILING */
30 #if defined(TICKY_TICKY)
33 #else /* !TICKY_TICKY */
36 #endif /* TICKY_TICKY */
52 * We are completely paranoid and make thread IDs 64 bits to avoid
53 * having to worry about overflow. A little calculation shows that
54 * even doing 10^6 forks per second would take 35 million years to
55 * overflow a 64 bit thread ID :-)
58 typedef StgWord32 StgThreadID;
61 * This type is returned to the scheduler by a thread that has
62 * stopped for one reason or another.
66 HeapOverflow, /* might also be StackOverflow */
71 } StgThreadReturnCode;
74 * Threads may be blocked for several reasons. A blocked thread will
75 * have the reason in the why_blocked field of the TSO, and some
76 * further info (such as the closure the thread is blocked on, or the
77 * file descriptor if the thread is waiting on I/O) in the block_info
99 * TSOs live on the heap, and therefore look just like heap objects.
100 * Large TSOs will live in their own "block group" allocated by the
101 * storage manager, and won't be copied during garbage collection.
104 typedef struct StgTSO_ {
106 struct StgTSO_* link;
107 StgMutClosure * mut_link; /* TSO's are mutable of course! */
108 StgTSOWhatNext whatNext;
109 StgTSOBlockReason why_blocked;
110 StgTSOBlockInfo block_info;
111 struct StgTSO_* blocked_exceptions;
113 StgTSOTickyInfo ticky;
118 /* The thread stack... */
119 StgWord stack_size; /* stack size in *words* */
120 StgWord max_stack_size; /* maximum stack size in *words* */
128 /* -----------------------------------------------------------------------------
131 An active thread has the following properties:
133 tso->stack < tso->sp < tso->stack+tso->stack_size
134 tso->stack_size <= tso->max_stack_size
135 tso->splim == tso->stack + RESERVED_STACK_WORDS;
137 RESERVED_STACK_WORDS is large enough for any heap-check or
140 The size of the TSO struct plus the stack is either
141 (a) smaller than a block, or
142 (b) a multiple of BLOCK_SIZE
144 tso->block_reason tso->block_info location
145 ----------------------------------------------------------------------
146 NotBlocked NULL runnable_queue, or running
148 BlockedOnBlackHole the BLACKHOLE_BQ the BLACKHOLE_BQ's queue
150 BlockedOnMVar the MVAR the MVAR's queue
152 BlockedOnException the TSO TSO->blocked_exception
154 BlockedOnRead NULL blocked_queue
155 BlockedOnWrite NULL blocked_queue
156 BlockedOnDelay NULL blocked_queue
158 tso->link == END_TSO_QUEUE, if the thread is currently running.
160 A zombie thread has the following properties:
162 tso->whatNext == ThreadComplete or ThreadKilled
163 tso->link == (could be on some queue somewhere)
164 tso->su == tso->stack + tso->stack_size
165 tso->sp == tso->stack + tso->stack_size - 1 (i.e. top stack word)
166 tso->sp[0] == return value of thread, if whatNext == ThreadComplete,
167 exception , if whatNext == ThreadKilled
169 (tso->sp is left pointing at the top word on the stack so that
170 the return value or exception will be retained by a GC).
172 tso->blocked_exceptions is either:
174 NULL if async exceptions are unblocked.
176 END_TSO_QUEUE if async exceptions are blocked, but no threads
177 are currently waiting to deliver.
179 (StgTSO *)tso if threads are currently awaiting delivery of
180 exceptions to this thread.
182 ---------------------------------------------------------------------------- */
184 /* Workaround for a bug/quirk in gcc on certain architectures.
185 * symptom is that (&tso->stack - &tso->header) /= sizeof(StgTSO)
186 * in other words, gcc pads the structure at the end.
189 extern StgTSO dummy_tso;
191 #define TSO_STRUCT_SIZE \
192 ((int)&(dummy_tso).stack - (int)&(dummy_tso).header)
194 #define TSO_STRUCT_SIZEW (TSO_STRUCT_SIZE / sizeof(W_))