#367: Infinite loops can hang Concurrent Haskell
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Reporter: simonpj | Owner: ezyang
Type: bug | Status: new
Priority: lowest | Milestone: _|_
Component: Compiler | Version: 6.4.1
Resolution: None | Keywords: scheduler
allocation
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: | Related:
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Comment(by ezyang):
OK, once I get my validate running (failing, due to a certain someone,
wink), I will push the patch, plus this docu patch:
{{{
<varlistentry>
<term>
<option>-falways-yield</option>
<indexterm><primary><option>-falways-
yield</option></primary></indexterm>
</term>
<listitem>
<para>Tells GHC to always emit a pre-emption check on entry
points to functions. This means that threads that run in tight
non-allocating loops will get preempted in a timely fashion;
otherwise, GHC may never manage to interrupt such a loop. This
imposes a very slight performance impact but inflates binary sizes
by about 5%, so it is not enabled by default. Note that if you
would like to guarantee that threads can always be interrupted,
you will need to compile all libraries with this flag.</para>
</listitem>
</varlistentry>
}}}
What are we going to do with information about CPU hogging primitives?
There are lots of unsafe primitives which can cause GHC to segfault or
jump to arbitrary code, so mostly this information would have to be
advisory for Safe Haskell implementors, who would know if one of these
primitives were called it better be doing bounds checks, etc. We can't
forcibly terminate the primops, since they're fat machine instructions and
don't give up the capability?
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/367#comment:31>
GHC <http://www.haskell.org/ghc/>
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