Parallel recompilation: fix concurrency issues.

Parallel recompilation: fix concurrency issues.


BUG=

Committed: https://code.google.com/p/v8/source/detail?r=13949

[Yang, 2013-03-14 12:45:23]

In some cases, at any point during the time a function is being optimized on the
optimizing thread, the function may have been marked for OSR, compiled for OSR,
running on optimized code, deopted again, reopted, disabled for optimization,
etc.

That's why steps related to parallel recompilation cannot make assumptions on
how the function is marked or whether it has already been optimized. We simply
continue to optimize.

[Yang, 2013-03-14 12:55:43]

On 2013/03/14 12:45:23, Yang wrote:
> In some cases, at any point during the time a function is being optimized on
the
> optimizing thread, the function may have been marked for OSR, compiled for
OSR,
> running on optimized code, deopted again, reopted, disabled for optimization,
> etc.
> 
> That's why steps related to parallel recompilation cannot make assumptions on
> how the function is marked or whether it has already been optimized. We simply
> continue to optimize.

One particular problem I encountered, that lead to this fix is follows:

Function F and then G is put on queue and optimized in the parallel thread. Both
are therefore marked as ready for install. Before F gets installed though, the
execution thread has triggered OSR, F opts, deopts, reopts again, and is put on
queue for parallel optimization again. F is now marked as in queue and blocks
the output queue of the optimizing thread.
Meanwhile on the execution thread, we call G. G is still marked as ready for
install, so the builtin calls Runtime_InstallRecompiledCode, the runtime
function attempts to process the output queue (which is still blocked by F), so
G remains marked as ready for install, so the tail call into what should be
optimized code actually tail calls into the Runtime_InstallRecompiledCode again,
an infinite loop.

[Jakob Kummerow, 2013-03-14 15:10:38]

lgtm

[Yang, 2013-03-14 16:35:41]

Committed patchset #1 manually as r13949 (presubmit successful).