| 1 | package Thread; |
| 2 | |
| 3 | use strict; |
| 4 | use warnings; |
| 5 | no warnings 'redefine'; |
| 6 | |
| 7 | our $VERSION = '3.02'; |
| 8 | $VERSION = eval $VERSION; |
| 9 | |
| 10 | BEGIN { |
| 11 | use Config; |
| 12 | if (! $Config{useithreads}) { |
| 13 | die("This Perl not built to support threads\n"); |
| 14 | } |
| 15 | } |
| 16 | |
| 17 | use threads 'yield'; |
| 18 | use threads::shared; |
| 19 | |
| 20 | require Exporter; |
| 21 | our @ISA = qw(Exporter threads); |
| 22 | our @EXPORT = qw(cond_wait cond_broadcast cond_signal); |
| 23 | our @EXPORT_OK = qw(async yield); |
| 24 | |
| 25 | sub async (&;@) { return Thread->new(shift); } |
| 26 | |
| 27 | sub done { return ! shift->is_running(); } |
| 28 | |
| 29 | sub eval { die("'eval' not implemented with 'ithreads'\n"); }; |
| 30 | sub flags { die("'flags' not implemented with 'ithreads'\n"); }; |
| 31 | |
| 32 | 1; |
| 33 | |
| 34 | __END__ |
| 35 | |
| 36 | =head1 NAME |
| 37 | |
| 38 | Thread - Manipulate threads in Perl (for old code only) |
| 39 | |
| 40 | =head1 DEPRECATED |
| 41 | |
| 42 | The C<Thread> module served as the frontend to the old-style thread model, |
| 43 | called I<5005threads>, that was introduced in release 5.005. That model was |
| 44 | deprecated, and has been removed in version 5.10. |
| 45 | |
| 46 | For old code and interim backwards compatibility, the C<Thread> module has |
| 47 | been reworked to function as a frontend for the new interpreter threads |
| 48 | (I<ithreads>) model. However, some previous functionality is not available. |
| 49 | Further, the data sharing models between the two thread models are completely |
| 50 | different, and anything to do with data sharing has to be thought differently. |
| 51 | With I<ithreads>, you must explicitly C<share()> variables between the |
| 52 | threads. |
| 53 | |
| 54 | You are strongly encouraged to migrate any existing threaded code to the new |
| 55 | model (i.e., use the C<threads> and C<threads::shared> modules) as soon as |
| 56 | possible. |
| 57 | |
| 58 | =head1 HISTORY |
| 59 | |
| 60 | In Perl 5.005, the thread model was that all data is implicitly shared, and |
| 61 | shared access to data has to be explicitly synchronized. This model is called |
| 62 | I<5005threads>. |
| 63 | |
| 64 | In Perl 5.6, a new model was introduced in which all is was thread local and |
| 65 | shared access to data has to be explicitly declared. This model is called |
| 66 | I<ithreads>, for "interpreter threads". |
| 67 | |
| 68 | In Perl 5.6, the I<ithreads> model was not available as a public API; only as |
| 69 | an internal API that was available for extension writers, and to implement |
| 70 | fork() emulation on Win32 platforms. |
| 71 | |
| 72 | In Perl 5.8, the I<ithreads> model became available through the C<threads> |
| 73 | module, and the I<5005threads> model was deprecated. |
| 74 | |
| 75 | In Perl 5.10, the I<5005threads> model was removed from the Perl interpreter. |
| 76 | |
| 77 | =head1 SYNOPSIS |
| 78 | |
| 79 | use Thread qw(:DEFAULT async yield); |
| 80 | |
| 81 | my $t = Thread->new(\&start_sub, @start_args); |
| 82 | |
| 83 | $result = $t->join; |
| 84 | $t->detach; |
| 85 | |
| 86 | if ($t->done) { |
| 87 | $t->join; |
| 88 | } |
| 89 | |
| 90 | if($t->equal($another_thread)) { |
| 91 | # ... |
| 92 | } |
| 93 | |
| 94 | yield(); |
| 95 | |
| 96 | my $tid = Thread->self->tid; |
| 97 | |
| 98 | lock($scalar); |
| 99 | lock(@array); |
| 100 | lock(%hash); |
| 101 | |
| 102 | my @list = Thread->list; |
| 103 | |
| 104 | =head1 DESCRIPTION |
| 105 | |
| 106 | The C<Thread> module provides multithreading support for Perl. |
| 107 | |
| 108 | =head1 FUNCTIONS |
| 109 | |
| 110 | =over 8 |
| 111 | |
| 112 | =item $thread = Thread->new(\&start_sub) |
| 113 | |
| 114 | =item $thread = Thread->new(\&start_sub, LIST) |
| 115 | |
| 116 | C<new> starts a new thread of execution in the referenced subroutine. The |
| 117 | optional list is passed as parameters to the subroutine. Execution |
| 118 | continues in both the subroutine and the code after the C<new> call. |
| 119 | |
| 120 | C<Thread->new> returns a thread object representing the newly created |
| 121 | thread. |
| 122 | |
| 123 | =item lock VARIABLE |
| 124 | |
| 125 | C<lock> places a lock on a variable until the lock goes out of scope. |
| 126 | |
| 127 | If the variable is locked by another thread, the C<lock> call will |
| 128 | block until it's available. C<lock> is recursive, so multiple calls |
| 129 | to C<lock> are safe--the variable will remain locked until the |
| 130 | outermost lock on the variable goes out of scope. |
| 131 | |
| 132 | Locks on variables only affect C<lock> calls--they do I<not> affect normal |
| 133 | access to a variable. (Locks on subs are different, and covered in a bit.) |
| 134 | If you really, I<really> want locks to block access, then go ahead and tie |
| 135 | them to something and manage this yourself. This is done on purpose. |
| 136 | While managing access to variables is a good thing, Perl doesn't force |
| 137 | you out of its living room... |
| 138 | |
| 139 | If a container object, such as a hash or array, is locked, all the |
| 140 | elements of that container are not locked. For example, if a thread |
| 141 | does a C<lock @a>, any other thread doing a C<lock($a[12])> won't |
| 142 | block. |
| 143 | |
| 144 | Finally, C<lock> will traverse up references exactly I<one> level. |
| 145 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. |
| 146 | |
| 147 | =item async BLOCK; |
| 148 | |
| 149 | C<async> creates a thread to execute the block immediately following |
| 150 | it. This block is treated as an anonymous sub, and so must have a |
| 151 | semi-colon after the closing brace. Like C<Thread->new>, C<async> |
| 152 | returns a thread object. |
| 153 | |
| 154 | =item Thread->self |
| 155 | |
| 156 | The C<Thread-E<gt>self> function returns a thread object that represents |
| 157 | the thread making the C<Thread-E<gt>self> call. |
| 158 | |
| 159 | =item Thread->list |
| 160 | |
| 161 | Returns a list of all non-joined, non-detached Thread objects. |
| 162 | |
| 163 | =item cond_wait VARIABLE |
| 164 | |
| 165 | The C<cond_wait> function takes a B<locked> variable as |
| 166 | a parameter, unlocks the variable, and blocks until another thread |
| 167 | does a C<cond_signal> or C<cond_broadcast> for that same locked |
| 168 | variable. The variable that C<cond_wait> blocked on is relocked |
| 169 | after the C<cond_wait> is satisfied. If there are multiple threads |
| 170 | C<cond_wait>ing on the same variable, all but one will reblock waiting |
| 171 | to reaquire the lock on the variable. (So if you're only using |
| 172 | C<cond_wait> for synchronization, give up the lock as soon as |
| 173 | possible.) |
| 174 | |
| 175 | =item cond_signal VARIABLE |
| 176 | |
| 177 | The C<cond_signal> function takes a locked variable as a parameter and |
| 178 | unblocks one thread that's C<cond_wait>ing on that variable. If more than |
| 179 | one thread is blocked in a C<cond_wait> on that variable, only one (and |
| 180 | which one is indeterminate) will be unblocked. |
| 181 | |
| 182 | If there are no threads blocked in a C<cond_wait> on the variable, |
| 183 | the signal is discarded. |
| 184 | |
| 185 | =item cond_broadcast VARIABLE |
| 186 | |
| 187 | The C<cond_broadcast> function works similarly to C<cond_signal>. |
| 188 | C<cond_broadcast>, though, will unblock B<all> the threads that are |
| 189 | blocked in a C<cond_wait> on the locked variable, rather than only |
| 190 | one. |
| 191 | |
| 192 | =item yield |
| 193 | |
| 194 | The C<yield> function allows another thread to take control of the |
| 195 | CPU. The exact results are implementation-dependent. |
| 196 | |
| 197 | =back |
| 198 | |
| 199 | =head1 METHODS |
| 200 | |
| 201 | =over 8 |
| 202 | |
| 203 | =item join |
| 204 | |
| 205 | C<join> waits for a thread to end and returns any values the thread |
| 206 | exited with. C<join> will block until the thread has ended, though |
| 207 | it won't block if the thread has already terminated. |
| 208 | |
| 209 | If the thread being C<join>ed C<die>d, the error it died with will |
| 210 | be returned at this time. If you don't want the thread performing |
| 211 | the C<join> to die as well, you should either wrap the C<join> in |
| 212 | an C<eval> or use the C<eval> thread method instead of C<join>. |
| 213 | |
| 214 | =item detach |
| 215 | |
| 216 | C<detach> tells a thread that it is never going to be joined i.e. |
| 217 | that all traces of its existence can be removed once it stops running. |
| 218 | Errors in detached threads will not be visible anywhere - if you want |
| 219 | to catch them, you should use $SIG{__DIE__} or something like that. |
| 220 | |
| 221 | =item equal |
| 222 | |
| 223 | C<equal> tests whether two thread objects represent the same thread and |
| 224 | returns true if they do. |
| 225 | |
| 226 | =item tid |
| 227 | |
| 228 | The C<tid> method returns the tid of a thread. The tid is |
| 229 | a monotonically increasing integer assigned when a thread is |
| 230 | created. The main thread of a program will have a tid of zero, |
| 231 | while subsequent threads will have tids assigned starting with one. |
| 232 | |
| 233 | =item done |
| 234 | |
| 235 | The C<done> method returns true if the thread you're checking has |
| 236 | finished, and false otherwise. |
| 237 | |
| 238 | =back |
| 239 | |
| 240 | =head1 DEFUNCT |
| 241 | |
| 242 | The following were implemented with I<5005threads>, but are no longer |
| 243 | available with I<ithreads>. |
| 244 | |
| 245 | =over 8 |
| 246 | |
| 247 | =item lock(\&sub) |
| 248 | |
| 249 | With 5005threads, you could also C<lock> a sub such that any calls to that sub |
| 250 | from another thread would block until the lock was released. |
| 251 | |
| 252 | Also, subroutines could be declared with the C<:locked> attribute which would |
| 253 | serialize access to the subroutine, but allowed different threads |
| 254 | non-simultaneous access. |
| 255 | |
| 256 | =item eval |
| 257 | |
| 258 | The C<eval> method wrapped an C<eval> around a C<join>, and so waited for a |
| 259 | thread to exit, passing along any values the thread might have returned and |
| 260 | placing any errors into C<$@>. |
| 261 | |
| 262 | =item flags |
| 263 | |
| 264 | The C<flags> method returned the flags for the thread - an integer value |
| 265 | corresponding to the internal flags for the thread. |
| 266 | |
| 267 | =back |
| 268 | |
| 269 | =head1 SEE ALSO |
| 270 | |
| 271 | L<threads>, L<threads::shared>, L<Thread::Queue>, L<Thread::Semaphore> |
| 272 | |
| 273 | =cut |