forks-0.21

Changes for version 0.21

This revision includes *many* core changes and improvements, so be sure to perform full testing with existing forks-enabled applications before upgrading.
All changes have been exposed to extensive regression testing, so you may expect all new features to be reasonably stable unless otherwise noted with a *WARNING* tag.
New features *****
Enabled complete thread context support. Be sure to specify the context, either implicit or directly. This also means you may not get what you expect if you return values in a context that doesn't match your spec.
Add optional, automatic deadlock detection (warnings) in threads::shared. Also added is_deadlocked() method (manual deadlock detection) for threads.
Added set_deadlock_option class method to forks::shared (threads::shared).
Aware of thread params at thread creation, e.g. threads->new({}, sub {});
Added complete support for $thr->wantarray and thread->wantarray.
Added complete support for thread state: is_running, is_joinable, is_detached().
Added additional support to threads->list(), with package variables: threads::all, threads::running, and threads::joinable.
Added support for 'use forks qw(stringify)'where the TID is returned for a threads object in string context.
Added detailed last known state of all threads on main thread exit (or server process unexpected exit), like: Perl exited with active threads: x running and unjoined y finished and unjoined z running and detached
Added stubs for get_stack_size and set_stack_size, although they don't do anything (yet).
Added support for threads->_handle and $thr->_handle, although it currently does not guarantee a reference to the same memory address each time (will be addressed in a later release).
Added support for inter-thread signaling using $thr->kill('SIG...'). *WARNING* This feature is still highly experimental and has known issues when sending a signal to a process sending or receiving socket data pertaining to a threads operation. This will be addressed in a future release.
Added question during build process to allow forks to override threads namespace if target Perl does not have native threading built in. Added POD describing this feature and behavior implications.
Bug fixes *****
Corrected bug in threads::shared::scalar that prevented tieing without a pre-existing scalar reference.
Localizing $? in END block to insure that main thread exit code isn't accidentally overwritten during shutdown.
Corrected several cases where internal auto-vivification was not intended, but might cause internal variable state issues.
Corrected bug where fork() followed by ->isthread() in a child process while parent process (a thread) was already waiting on a separate thread could cause internal synchronization issues.
Corrected bug in ->list where scalar context would return last object, not the number of waiting threads.
Added additional protection in END block against external fork() occuring outside our knowledge causing synchronization havoc with the thread process group.
Removed delete from %DETACHED on thread exit, as this property is used for internal thread type and state checking.
Updated some error handling to suppress some undefined variable warnings.
Internal behavior improvements *****
Added silent overload of Config.pm 'useithreads' property to insure all modules and scripts see a true value when forks is loaded.
Added explicit signal trapping of all untrapped normal and error signals for consistent and safe thread exit behavior.
Added defensive error handling around non-blocking server sockets to protect against interruptions or busy resources during read or write. This should also make UNIX socket support more stable on certain target architectures.
Added defensive logic to cleanup internal resources for threads that appear to have exited in an unsafe manner (and that may have left forks::shared resources in a unclean state) or were terminated with SIGKILL.
Rewrote _length(), _send(), and _receive() internal functions to protect against signal interruptions, busy resources, socket disconnections, full socket buffers, and miscellaneous socket errors, including adding retry logic where appropriate.
Updated _join() server function with much more intelligent logic regarding the state of a thread during the join process and a few more error cases that it needed to check for.
threads->yield() now does a 1 ms sleep.
Threads API consistency changes *****
Can now signal unlocked variable using cond_signal and cond_broadcast. Note: Signaling locked returns 1; signaling unlocked returns undef.
Modified lock, cond_signal, and cond_broadcast to return undef (instead of 1) to be consistent with threads.pm.
Overloaded != for thread objects.
A failed thread spawn (fork) now prints a warning and returns undef instead of dieing out.
Detach twice on the same thread now throws an error.
Improved format and content of internal warnings, and warnings now respect warnings state in caller for category 'threads'.
Bumped threads $VERSION to 1.26, threads::shared to 1.04 to match version-supported features and behavior.
Miscellaneous changes ***
Implemented initial framework for better message handling. This should help reduce overall CPU usage, and hopefully improve performance, using custom filter definition for request and response messages that do not require Storable freeze/thaw. Requests that currently implement this are: _lock and _unlock. Responses that currently implement this are: any generic boolean response.
Made Time::HiRes a prerequisite now. This means that fractional cond_timedwait is now supported by default.
Optimized sigset masking: now only one set is created at compile time and reused during execution.
Now safely runs in taint mode when any potentially tainted environment vars are defined.
Suppressing unnecessary warnings in the case that 'test' does not exist in /bin or /usr/bin.
Silenced thread socket errors during thread shutdown process, unless debugging is enabled.
Added basic blocking join poll checks, to help prevent against forever blocking join() cases in abnormal thread death circumstances.
Thread shutdown now expects a response (to insure synchronized shutdown agreement with server process).
General improvements in thread shutdown stability (primarily server-side).