X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=rts%2Fsm%2FMarkWeak.c;h=f4b576ac735bed0b1f12a3b1ea70fc08473cc963;hp=78c84ed77aaa8da0a4a13c15f7e5cdf66c855064;hb=bef3da1e26639303fccbf26c312d2833eedb486e;hpb=c151739a1831546baa9c3f4a55f93ffc0b38bf9d diff --git a/rts/sm/MarkWeak.c b/rts/sm/MarkWeak.c index 78c84ed..f4b576a 100644 --- a/rts/sm/MarkWeak.c +++ b/rts/sm/MarkWeak.c @@ -11,14 +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 @@ -77,8 +81,8 @@ StgWeak *old_weak_ptr_list; // also pending finaliser list // List of threads found to be unreachable StgTSO *resurrected_threads; -// List of blocked threads found to have pending throwTos -StgTSO *exception_threads; +static void resurrectUnreachableThreads (generation *gen); +static rtsBool tidyThreadList (generation *gen); void initWeakForGC(void) @@ -87,7 +91,6 @@ initWeakForGC(void) weak_ptr_list = NULL; weak_stage = WeakPtrs; resurrected_threads = END_TSO_QUEUE; - exception_threads = END_TSO_QUEUE; } rtsBool @@ -107,7 +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). */ - gct->evac_step = 0; + gct->evac_gen_no = 0; last_w = &old_weak_ptr_list; for (w = old_weak_ptr_list; w != NULL; w = next_w) { @@ -121,14 +124,8 @@ traverseWeakPtrList(void) continue; } - info = w->header.info; - if (IS_FORWARDING_PTR(info)) { - next_w = (StgWeak *)UN_FORWARDING_PTR(info); - *last_w = next_w; - continue; - } - - switch (INFO_PTR_TO_STRUCT(info)->type) { + info = get_itbl(w); + switch (info->type) { case WEAK: /* Now, check whether the key is reachable. @@ -180,86 +177,23 @@ 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, s; - step *stp; + { + nat g; - // Traverse thread lists for generations we collected... - for (g = 0; g <= N; g++) { - for (s = 0; s < generations[g].n_steps; s++) { - stp = &generations[g].steps[s]; - - prev = &stp->old_threads; - - for (t = stp->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; - - // This is a good place to check for blocked - // exceptions. It might be the case that a thread is - // blocked on delivering an exception to a thread that - // is also blocked - we try to ensure that this - // doesn't happen in throwTo(), but it's too hard (or - // impossible) to close all the race holes, so we - // accept that some might get through and deal with - // them here. A GC will always happen at some point, - // even if the system is otherwise deadlocked. - // - // If an unreachable thread has blocked - // exceptions, we really want to perform the - // blocked exceptions rather than throwing - // BlockedIndefinitely exceptions. This is the - // only place we can discover such threads. - // The target thread might even be - // ThreadFinished or ThreadKilled. Bugs here - // will only be seen when running on a - // multiprocessor. - if (t->blocked_exceptions != END_TSO_QUEUE) { - if (tmp == NULL) { - evacuate((StgClosure **)&t); - flag = rtsTrue; - } - t->global_link = exception_threads; - exception_threads = t; - *prev = next; - continue; - } - - 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. - step *new_step; - new_step = Bdescr((P_)t)->step; - t->global_link = new_step->threads; - new_step->threads = t; - } - } - } + // 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; } } @@ -270,131 +204,128 @@ traverseWeakPtrList(void) /* And resurrect any threads which were about to become garbage. */ { - nat g, s; - step *stp; - StgTSO *t, *tmp, *next; - + nat g; for (g = 0; g <= N; g++) { - for (s = 0; s < generations[g].n_steps; s++) { - stp = &generations[g].steps[s]; - - for (t = stp->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; - } - } - } + resurrectUnreachableThreads(&generations[g]); } } - - /* 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); - } - } - + 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; - nat type; - - flag = rtsFalse; - prev = NULL; - - for (t = blackhole_queue; t != END_TSO_QUEUE; prev=t, t = t->_link) { - // if the thread is not yet alive... - if (! (tmp = (StgTSO *)isAlive((StgClosure*)t))) { - // if the closure it is blocked on is either (a) a - // reachable BLAKCHOLE or (b) not a BLACKHOLE, then we - // make the thread alive. - if (!isAlive(t->block_info.closure)) { - type = get_itbl(t->block_info.closure)->type; - if (type == BLACKHOLE || type == CAF_BLACKHOLE) { - continue; - } - } - evacuate((StgClosure **)&t); - if (prev) { - prev->_link = t; - } else { - blackhole_queue = t; - } - // no write barrier when on the blackhole queue, - // because we traverse the whole queue on every GC. - 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); + next = t->global_link; + + // if the thread is not masking exceptions but there are + // pending exceptions on its queue, then something has gone + // wrong. However, pending exceptions are OK if there is an + // FFI call. + ASSERT(t->blocked_exceptions == END_BLOCKED_EXCEPTIONS_QUEUE + || t->why_blocked == BlockedOnCCall + || t->why_blocked == BlockedOnCCall_Interruptible + || (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 markWeakPtrList ( void ) { - StgWeak *w, **last_w, *tmp; + StgWeak *w, **last_w; 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(IS_FORWARDING_PTR(w->header.info) - || w->header.info == &stg_DEAD_WEAK_info - || get_itbl(w)->type == WEAK); - tmp = w; - evacuate((StgClosure **)&tmp); - *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); + } } }