1 /* ---------------------------------------------------------------------------
3 * (c) The GHC Team, 2001
7 * The notion of a capability is used when operating in multi-threaded
8 * environments (which the SMP and Threads builds of the RTS do), to
9 * hold all the state an OS thread/task needs to run Haskell code:
10 * its STG registers, a pointer to its TSO, a nursery etc. During
11 * STG execution, a pointer to the capabilitity is kept in a
14 * Only in an SMP build will there be multiple capabilities, the threaded
15 * RTS and other non-threaded builds, there is one global capability,
16 * namely MainRegTable.
19 * --------------------------------------------------------------------------*/
20 #include "PosixSource.h"
23 #include "Capability.h"
26 Capability MainCapability; /* for non-SMP, we have one global capability */
29 nat rts_n_free_capabilities;
33 initCapability( Capability *cap )
35 cap->f.stgChk0 = (F_)__stg_chk_0;
36 cap->f.stgChk1 = (F_)__stg_chk_1;
37 cap->f.stgGCEnter1 = (F_)__stg_gc_enter_1;
38 cap->f.stgUpdatePAP = (F_)__stg_update_PAP;
42 static void initCapabilities_(nat n);
51 initCapabilities_(RtsFlags.ParFlags.nNodes);
53 initCapability(&MainCapability);
59 /* Free capability list.
60 * Locks required: sched_mutex.
63 static Capability *free_capabilities; /* Available capabilities for running threads */
66 void grabCapability(Capability** cap)
69 rts_n_free_capabilities = 0;
70 *cap = &MainCapability;
72 *cap = free_capabilities;
73 free_capabilities = (*cap)->link;
74 rts_n_free_capabilities--;
78 void releaseCapability(Capability* cap)
81 cap->link = free_capabilities;
82 free_capabilities = cap;
83 rts_n_free_capabilities++;
85 rts_n_free_capabilities = 1;
90 /* Allocate 'n' capabilities */
92 initCapabilities_(nat n)
95 Capability *cap, *prev;
98 for (i = 0; i < n; i++) {
99 cap = stgMallocBytes(sizeof(Capability), "initCapabilities");
104 free_capabilities = cap;
105 rts_n_free_capabilities = n;
106 IF_DEBUG(scheduler,fprintf(stderr,"scheduler: Allocated %d capabilities\n", n_free_capabilities););