Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : ghc-7.4
http://hackage.haskell.org/trac/ghc/changeset/20906163a6aee2b76de240c4171928f83a5d9077 >--------------------------------------------------------------- commit 20906163a6aee2b76de240c4171928f83a5d9077 Author: Simon Marlow <[email protected]> Date: Wed Mar 28 11:45:39 2012 +0100 Fix a bug in threadStackOverflow() (maybe #5214) If we overflow the current stack chunk and copy its entire contents into the next stack chunk, we could end up with two UNDERFLOW_FRAMEs. We had a special case to catch this in the case when the old stack chunk was the last one (ending in STOP_FRAME), but it went wrong for other chunks. I found this bug while poking around in the core dump attached to options and running the nofib suite: imaginary/wheel_sieve2 crashed with +RTS -kc600 -kb300. I don't know if this is the cause of all the symptoms reported in MERGED from commit 734f1d484b12b785795b249b4116cfb4817ab55d >--------------------------------------------------------------- rts/Threads.c | 35 ++++++++++++++++++++++------------- 1 files changed, 22 insertions(+), 13 deletions(-) diff --git a/rts/Threads.c b/rts/Threads.c index 5488a32..fc520c6 100644 --- a/rts/Threads.c +++ b/rts/Threads.c @@ -579,11 +579,6 @@ threadStackOverflow (Capability *cap, StgTSO *tso) tso->tot_stack_size += new_stack->stack_size; - new_stack->sp -= sizeofW(StgUnderflowFrame); - frame = (StgUnderflowFrame*)new_stack->sp; - frame->info = &stg_stack_underflow_frame_info; - frame->next_chunk = old_stack; - { StgWord *sp; nat chunk_words, size; @@ -611,6 +606,28 @@ threadStackOverflow (Capability *cap, StgTSO *tso) sp += size; } + if (sp == old_stack->stack + old_stack->stack_size) { + // + // the old stack chunk is now empty, so we do *not* insert + // an underflow frame pointing back to it. There are two + // cases: either the old stack chunk was the last one, in + // which case it ends with a STOP_FRAME, or it is not the + // last one, and it already ends with an UNDERFLOW_FRAME + // pointing to the previous chunk. In the latter case, we + // will copy the UNDERFLOW_FRAME into the new stack chunk. + // In both cases, the old chunk will be subsequently GC'd. + // + // With the default settings, -ki1k -kb1k, this means the + // first stack chunk will be discarded after the first + // overflow, being replaced by a non-moving 32k chunk. + // + } else { + new_stack->sp -= sizeofW(StgUnderflowFrame); + frame = (StgUnderflowFrame*)new_stack->sp; + frame->info = &stg_stack_underflow_frame_info; + frame->next_chunk = old_stack; + } + // copy the stack chunk between tso->sp and sp to // new_tso->sp + (tso->sp - sp) chunk_words = sp - old_stack->sp; @@ -623,14 +640,6 @@ threadStackOverflow (Capability *cap, StgTSO *tso) new_stack->sp -= chunk_words; } - // if the old stack chunk is now empty, discard it. With the - // default settings, -ki1k -kb1k, this means the first stack chunk - // will be discarded after the first overflow, being replaced by a - // non-moving 32k chunk. - if (old_stack->sp == old_stack->stack + old_stack->stack_size) { - frame->next_chunk = (StgStack*)END_TSO_QUEUE; // dummy - } - tso->stackobj = new_stack; // we're about to run it, better mark it dirty _______________________________________________ Cvs-ghc mailing list [email protected] http://www.haskell.org/mailman/listinfo/cvs-ghc
