Thread status constants

[Jost Berthold]

I'm afraid so - I am just creating the ticket.

/ jost


On 07/19/2014 09:07 PM, Carter Schonwald wrote:
> Wait, does that mean the corresponding constants in base for 7.8.3 are
> busted?
>
> On Saturday, July 19, 2014, Jost Berthold
> <berthold at mathematik.uni-marburg.de
> <mailto:berthold at mathematik.uni-marburg.de>> wrote:
>
>         Message: 2
>         Date: Sat, 19 Jul 2014 15:00:17 +1000
>         From: Kyle Van Berendonck <kvanberendonck at gmail.com>
>         To: "ghc-devs at haskell.org" <ghc-devs at haskell.org>
>         Subject: Thread status constants
>         Message-ID:
>
>         <CAFSvR6A3maSWngY=__GJdATvGPjTAyuPokXZ5=rLtLT=EbYdSLKA at mail.gmail.com>
>         Content-Type: text/plain; charset="utf-8"
>
>         Hi,
>
>         I found these:
>         https://github.com/ghc/ghc/__blob/__5f3c5384df59717ca8013c5df8d1f6__5692867825/includes/rts/__Constants.h#L194
>         <https://github.com/ghc/ghc/blob/5f3c5384df59717ca8013c5df8d1f65692867825/includes/rts/Constants.h#L194>
>
>         They go only 0-14, so there's some long chains of branches and
>         stuff in hot
>         paths that could be cleaned up into single &-masked branches by
>         changing
>         these into a set of flags.
>
>         And then I saw these:
>         https://github.com/ghc/ghc/__blob/master/libraries/base/__GHC/Conc/Sync.lhs#L483
>         <https://github.com/ghc/ghc/blob/master/libraries/base/GHC/Conc/Sync.lhs#L483>
>
>         Where does 16 and 17 come from -- I couldn't find them in the
>         header files
>         anywhere?
>
>         Kyle
>
>
>     Hi Kyle,
>
>     I had a look at these constants just recently.
>
>     About 16 and 17, see here:
>     https://github.com/ghc/ghc/__blob/master/rts/PrimOps.cmm#__L853
>     <https://github.com/ghc/ghc/blob/master/rts/PrimOps.cmm#L853>
>
>     About the others:The block reasons received two updates just recently.
>     Turns out that the eventlog (GHC's post-mortem tracing for
>     threadscope et al.) expects these states to have particular values
>     (those in includes/rts/Constants.h, consider them a fixed ABI for
>     the time being).
>     See here for the story:
>     https://ghc.haskell.org/trac/__ghc/ticket/9003
>     <https://ghc.haskell.org/trac/ghc/ticket/9003>
>
>     NB: Darn... base still uses GHC-7.8.2 constants. Thanks for the pointer!
>
>     About your proposal to use bit masks:
>
>     Did you find some of those hot paths?
>     I believe (believe, unchecked...) that there are not too many places
>     where a complete switch over all possible reasons is done (apart
>     from debug output maybe); the typical use is rather to compare to
>     one single constant than to all. So the performance might not
>     increase too much from optimisations. Again, just a hunch, not verified.
>
>     If the RTS contains code specialised to the current constants, these
>     places need to be kept symbolic, to avoid future breakage when new
>     states are added.
>
>     A fix which removes the tight implicit dependency of ghc-events from
>     the constants in includes/rts/Constants.h is pending, btw.
>
>     / Jost
>
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