X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=rts%2Fsm%2FMarkWeak.c;h=e65c176c0a2027bf2628f042360df276b706a612;hb=9fa96fc44a640014415e1588f50ab7689285e6cb;hp=49134da826150698a1c7a6fd3ce772d68d920d15;hpb=64c17c4561cf419a4c70511bafc0815ea670bb2e;p=ghc-hetmet.git diff --git a/rts/sm/MarkWeak.c b/rts/sm/MarkWeak.c index 49134da..e65c176 100644 --- a/rts/sm/MarkWeak.c +++ b/rts/sm/MarkWeak.c @@ -1,6 +1,6 @@ /* ----------------------------------------------------------------------------- * - * (c) The GHC Team 1998-2006 + * (c) The GHC Team 1998-2008 * * Weak pointers and weak-like things in the GC * @@ -11,13 +11,18 @@ * * ---------------------------------------------------------------------------*/ +#include "PosixSource.h" #include "Rts.h" -#include "Storage.h" + #include "MarkWeak.h" #include "GC.h" +#include "GCThread.h" #include "Evac.h" #include "Trace.h" #include "Schedule.h" +#include "Weak.h" +#include "Storage.h" +#include "Threads.h" /* ----------------------------------------------------------------------------- Weak Pointers @@ -73,10 +78,11 @@ static WeakStage weak_stage; */ StgWeak *old_weak_ptr_list; // also pending finaliser list -/* List of all threads during GC - */ +// List of threads found to be unreachable StgTSO *resurrected_threads; -static StgTSO *old_all_threads; + +static void resurrectUnreachableThreads (generation *gen); +static rtsBool tidyThreadList (generation *gen); void initWeakForGC(void) @@ -84,12 +90,6 @@ initWeakForGC(void) old_weak_ptr_list = weak_ptr_list; weak_ptr_list = NULL; weak_stage = WeakPtrs; - - /* The all_threads list is like the weak_ptr_list. - * See traverseWeakPtrList() for the details. - */ - old_all_threads = all_threads; - all_threads = END_TSO_QUEUE; resurrected_threads = END_TSO_QUEUE; } @@ -99,6 +99,7 @@ traverseWeakPtrList(void) StgWeak *w, **last_w, *next_w; StgClosure *new; rtsBool flag = rtsFalse; + const StgInfoTable *info; switch (weak_stage) { @@ -109,7 +110,7 @@ traverseWeakPtrList(void) /* doesn't matter where we evacuate values/finalizers to, since * these pointers are treated as roots (iff the keys are alive). */ - evac_gen = 0; + gct->evac_gen = 0; last_w = &old_weak_ptr_list; for (w = old_weak_ptr_list; w != NULL; w = next_w) { @@ -123,12 +124,8 @@ traverseWeakPtrList(void) continue; } - switch (get_itbl(w)->type) { - - case EVACUATED: - next_w = (StgWeak *)((StgEvacuated *)w)->evacuee; - *last_w = next_w; - continue; + info = get_itbl(w); + switch (info->type) { case WEAK: /* Now, check whether the key is reachable. @@ -137,8 +134,8 @@ traverseWeakPtrList(void) if (new != NULL) { w->key = new; // evacuate the value and finalizer - w->value = evacuate(w->value); - w->finalizer = evacuate(w->finalizer); + evacuate(&w->value); + evacuate(&w->finalizer); // remove this weak ptr from the old_weak_ptr list *last_w = w->link; // and put it on the new weak ptr list @@ -169,7 +166,7 @@ traverseWeakPtrList(void) */ if (flag == rtsFalse) { for (w = old_weak_ptr_list; w; w = w->link) { - w->finalizer = evacuate(w->finalizer); + evacuate(&w->finalizer); } // Next, move to the WeakThreads stage after fully @@ -180,57 +177,26 @@ traverseWeakPtrList(void) return rtsTrue; case WeakThreads: - /* Now deal with the all_threads list, which behaves somewhat like + /* Now deal with the step->threads lists, which behave somewhat like * the weak ptr list. If we discover any threads that are about to * become garbage, we wake them up and administer an exception. */ - { - StgTSO *t, *tmp, *next, **prev; + { + nat g; - prev = &old_all_threads; - for (t = old_all_threads; t != END_TSO_QUEUE; t = next) { - - tmp = (StgTSO *)isAlive((StgClosure *)t); - - if (tmp != NULL) { - t = tmp; - } - - ASSERT(get_itbl(t)->type == TSO); - switch (t->what_next) { - case ThreadRelocated: - next = t->link; - *prev = next; - continue; - case ThreadKilled: - case ThreadComplete: - // finshed or died. The thread might still be alive, but we - // don't keep it on the all_threads list. Don't forget to - // stub out its global_link field. - next = t->global_link; - t->global_link = END_TSO_QUEUE; - *prev = next; - continue; - default: - ; - } - - if (tmp == NULL) { - // not alive (yet): leave this thread on the - // old_all_threads list. - prev = &(t->global_link); - next = t->global_link; - } - else { - // alive: move this thread onto the all_threads list. - next = t->global_link; - t->global_link = all_threads; - all_threads = t; - *prev = next; - } - } + // Traverse thread lists for generations we collected... +// ToDo when we have one gen per capability: +// for (n = 0; n < n_capabilities; n++) { +// if (tidyThreadList(&nurseries[n])) { +// flag = rtsTrue; +// } +// } + for (g = 0; g <= N; g++) { + if (tidyThreadList(&generations[g])) { + flag = rtsTrue; + } } - + /* If we evacuated any threads, we need to go back to the scavenger. */ if (flag) return rtsTrue; @@ -238,78 +204,102 @@ traverseWeakPtrList(void) /* And resurrect any threads which were about to become garbage. */ { - StgTSO *t, *tmp, *next; - for (t = old_all_threads; t != END_TSO_QUEUE; t = next) { - next = t->global_link; - tmp = (StgTSO *)evacuate((StgClosure *)t); - tmp->global_link = resurrected_threads; - resurrected_threads = tmp; - } - } - - /* Finally, we can update the blackhole_queue. This queue - * simply strings together TSOs blocked on black holes, it is - * not intended to keep anything alive. Hence, we do not follow - * pointers on the blackhole_queue until now, when we have - * determined which TSOs are otherwise reachable. We know at - * this point that all TSOs have been evacuated, however. - */ - { - StgTSO **pt; - for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) { - *pt = (StgTSO *)isAlive((StgClosure *)*pt); - ASSERT(*pt != NULL); - } + nat g; + for (g = 0; g <= N; g++) { + resurrectUnreachableThreads(&generations[g]); + } } - + weak_stage = WeakDone; // *now* we're done, return rtsTrue; // but one more round of scavenging, please - + } + default: barf("traverse_weak_ptr_list"); return rtsTrue; } - +} + + static void resurrectUnreachableThreads (generation *gen) +{ + StgTSO *t, *tmp, *next; + + for (t = gen->old_threads; t != END_TSO_QUEUE; t = next) { + next = t->global_link; + + // ThreadFinished and ThreadComplete: we have to keep + // these on the all_threads list until they + // become garbage, because they might get + // pending exceptions. + switch (t->what_next) { + case ThreadKilled: + case ThreadComplete: + continue; + default: + tmp = t; + evacuate((StgClosure **)&tmp); + tmp->global_link = resurrected_threads; + resurrected_threads = tmp; + } + } } -/* ----------------------------------------------------------------------------- - The blackhole queue - - Threads on this list behave like weak pointers during the normal - phase of garbage collection: if the blackhole is reachable, then - the thread is reachable too. - -------------------------------------------------------------------------- */ -rtsBool -traverseBlackholeQueue (void) +static rtsBool tidyThreadList (generation *gen) { - StgTSO *prev, *t, *tmp; - rtsBool flag; - - flag = rtsFalse; - prev = NULL; - - for (t = blackhole_queue; t != END_TSO_QUEUE; prev=t, t = t->link) { - if (! (tmp = (StgTSO *)isAlive((StgClosure*)t))) { - if (isAlive(t->block_info.closure)) { - t = (StgTSO *)evacuate((StgClosure *)t); - if (prev) prev->link = t; - flag = rtsTrue; - } - } + StgTSO *t, *tmp, *next, **prev; + rtsBool flag = rtsFalse; + + prev = &gen->old_threads; + + for (t = gen->old_threads; t != END_TSO_QUEUE; t = next) { + + tmp = (StgTSO *)isAlive((StgClosure *)t); + + if (tmp != NULL) { + t = tmp; + } + + ASSERT(get_itbl(t)->type == TSO); + if (t->what_next == ThreadRelocated) { + next = t->_link; + *prev = next; + continue; + } + + next = t->global_link; + + // if the thread is not masking exceptions but there are + // pending exceptions on its queue, then something has gone + // wrong: + ASSERT(t->blocked_exceptions == END_BLOCKED_EXCEPTIONS_QUEUE + || (t->flags & TSO_BLOCKEX)); + + if (tmp == NULL) { + // not alive (yet): leave this thread on the + // old_all_threads list. + prev = &(t->global_link); + } + else { + // alive + *prev = next; + + // move this thread onto the correct threads list. + generation *new_gen; + new_gen = Bdescr((P_)t)->gen; + t->global_link = new_gen->threads; + new_gen->threads = t; + } } + return flag; } /* ----------------------------------------------------------------------------- - After GC, the live weak pointer list may have forwarding pointers - on it, because a weak pointer object was evacuated after being - moved to the live weak pointer list. We remove those forwarding - pointers here. - - Also, we don't consider weak pointer objects to be reachable, but - we must nevertheless consider them to be "live" and retain them. - Therefore any weak pointer objects which haven't as yet been - evacuated need to be evacuated now. + Evacuate every weak pointer object on the weak_ptr_list, and update + the link fields. + + ToDo: with a lot of weak pointers, this will be expensive. We + should have a per-GC weak pointer list, just like threads. -------------------------------------------------------------------------- */ void @@ -320,11 +310,25 @@ markWeakPtrList ( void ) last_w = &weak_ptr_list; for (w = weak_ptr_list; w; w = w->link) { // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here - ASSERT(w->header.info == &stg_DEAD_WEAK_info - || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED); - w = (StgWeak *)evacuate((StgClosure *)w); - *last_w = w; - last_w = &(w->link); + +#ifdef DEBUG + { // careful to do this assertion only reading the info ptr + // once, because during parallel GC it might change under our feet. + const StgInfoTable *info; + info = w->header.info; + ASSERT(IS_FORWARDING_PTR(info) + || info == &stg_DEAD_WEAK_info + || INFO_PTR_TO_STRUCT(info)->type == WEAK); + } +#endif + + evacuate((StgClosure **)last_w); + w = *last_w; + if (w->header.info == &stg_DEAD_WEAK_info) { + last_w = &(((StgDeadWeak*)w)->link); + } else { + last_w = &(w->link); + } } }