Re: [commit: ghc] master: a fix for checkTSO(): the TSO could be a WHITEHOLE (65e46f1)

On 13/11/2012 16:43, Henrique Ferreiro wrote:
> commit 65e46f144f3d8b18de7264b0b099086153c68d6c
>
>     Author: Simon Marlow <[email protected] <mailto:[email protected]>>
>     Date:   Mon Nov 5 15:43:21 2012 +0000
>
>          a fix for checkTSO(): the TSO could be a WHITEHOLE
>
>      >---------------------------------------------------------------
>
>       rts/sm/Sanity.c |   13 ++++++++++---
>       1 files changed, 10 insertions(+), 3 deletions(-)
>
>     diff --git a/rts/sm/Sanity.c b/rts/sm/Sanity.c
>     index 6237662..a760e57 100644
>     --- a/rts/sm/Sanity.c
>     +++ b/rts/sm/Sanity.c
>     @@ -499,6 +499,9 @@ checkSTACK (StgStack *stack)
>       void
>       checkTSO(StgTSO *tso)
>       {
>     +    StgTSO *next;
>     +    const StgInfoTable *info;
>     +
>           if (tso->what_next == ThreadKilled) {
>             /* The garbage collector doesn't bother following any pointers
>              * from dead threads, so don't check sanity here.
>     @@ -506,9 +509,13 @@ checkTSO(StgTSO *tso)
>             return;
>           }
>
>     -    ASSERT(tso->_link == END_TSO_QUEUE ||
>     -           tso->_link->header.info <http://header.info> ==
>     &stg_MVAR_TSO_QUEUE_info ||
>     -           tso->_link->header.info <http://header.info> ==
>     &stg_TSO_info);
>     +    next = tso->_link;
>     +    info = (const StgInfoTable*) tso->header.info <http://header.info>;
>     +
>     +    ASSERT(next == END_TSO_QUEUE ||
>     +           info == &stg_MVAR_TSO_QUEUE_info ||
>     +           info == &stg_TSO_info ||
>     +           info == &stg_WHITEHOLE_info); // happens due to STM
>     doing lockTSO()
>
>           if (   tso->why_blocked == BlockedOnMVar
>              || tso->why_blocked == BlockedOnBlackHole
>
>
> I may be missing something but in the original code you are checking the
> info table of tso->_link and, in the new one, the info table of tso.

Well spotted, thanks.

Cheers,
	Simon