1 package threads::shared;
9 unless ($Config{useithreads}) {
10 my @caller = caller(2);
12 $caller[1] line $caller[2]:
14 This Perl hasn't been configured and built properly for the threads
15 module to work. (The 'useithreads' configuration option hasn't been used.)
17 Having threads support requires all of Perl and all of the modules in
18 the Perl installation to be rebuilt, it is not just a question of adding
19 the threads module. (In other words, threaded and non-threaded Perls
20 are binary incompatible.)
22 If you want to the use the threads module, please contact the people
25 Cannot continue, aborting.
31 our @ISA = qw(Exporter);
32 our @EXPORT = qw(share cond_wait cond_broadcast cond_signal _refcnt _id _thrcnt);
33 our $VERSION = '0.90';
35 if ($Config{'useithreads'}) {
36 *cond_wait = \&cond_wait_enabled;
37 *cond_signal = \&cond_signal_enabled;
38 *cond_broadcast = \&cond_broadcast_enabled;
40 XSLoader::load('threads::shared',$VERSION);
43 *share = \&share_disabled;
44 *cond_wait = \&cond_wait_disabled;
45 *cond_signal = \&cond_signal_disabled;
46 *cond_broadcast = \&cond_broadcast_disabled;
50 sub cond_wait_disabled { return @_ };
51 sub cond_signal_disabled { return @_};
52 sub cond_broadcast_disabled { return @_};
53 sub share_disabled { return @_}
55 $threads::shared::threads_shared = 1;
58 sub threads::shared::tie::SPLICE
60 die "Splice not implemented for shared arrays";
67 threads::shared - Perl extension for sharing data structures between threads
76 my($scalar, @array, %hash);
81 $hash{bar} = share({});
86 cond_broadcast(@array);
91 By default, variables are private to each thread, and each newly created
92 thread gets a private copy of each existing variable. This module allows
93 you to share variables across different threads (and pseudoforks on
94 win32). It is used together with the threads module.
98 C<share>, C<lock>, C<cond_wait>, C<cond_signal>, C<cond_broadcast>
106 C<share> takes a value and marks it as shared. You can share a scalar, array,
107 hash, scalar ref, array ref or hash ref. C<share> will return the shared value.
109 C<share> will traverse up references exactly I<one> level.
110 C<share(\$a)> is equivalent to C<share($a)>, while C<share(\\$a)> is not.
112 A variable can also be marked as shared at compile time by using the
113 C<shared> attribute: C<my $var : shared>.
117 C<lock> places a lock on a variable until the lock goes out of scope. If
118 the variable is locked by another thread, the C<lock> call will block until
119 it's available. C<lock> is recursive, so multiple calls to C<lock> are
120 safe -- the variable will remain locked until the outermost lock on the
121 variable goes out of scope.
123 If a container object, such as a hash or array, is locked, all the elements
124 of that container are not locked. For example, if a thread does a C<lock
125 @a>, any other thread doing a C<lock($a[12])> won't block.
127 C<lock> will traverse up references exactly I<one> level.
128 C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not.
130 Note that you cannot explicitly unlock a variable; you can only wait for
131 the lock to go out of scope. If you need more fine-grained control, see
132 L<threads::shared::semaphore>.
134 =item cond_wait VARIABLE
136 The C<cond_wait> function takes a B<locked> variable as a parameter,
137 unlocks the variable, and blocks until another thread does a C<cond_signal>
138 or C<cond_broadcast> for that same locked variable. The variable that
139 C<cond_wait> blocked on is relocked after the C<cond_wait> is satisfied.
140 If there are multiple threads C<cond_wait>ing on the same variable, all but
141 one will reblock waiting to reacquire the lock on the variable. (So if
142 you're only using C<cond_wait> for synchronisation, give up the lock as
143 soon as possible). The two actions of unlocking the variable and entering
144 the blocked wait state are atomic, The two actions of exiting from the
145 blocked wait state and relocking the variable are not.
147 It is important to note that the variable can be notified even if no
148 thread C<cond_signal> or C<cond_broadcast> on the variable. It is therefore
149 important to check the value of the variable and go back to waiting if the
150 requirement is not fulfilled.
152 =item cond_signal VARIABLE
154 The C<cond_signal> function takes a B<locked> variable as a parameter and
155 unblocks one thread that's C<cond_wait>ing on that variable. If more than
156 one thread is blocked in a C<cond_wait> on that variable, only one (and
157 which one is indeterminate) will be unblocked.
159 If there are no threads blocked in a C<cond_wait> on the variable, the
160 signal is discarded. By always locking before signaling, you can (with
161 care), avoid signaling before another thread has entered cond_wait().
163 C<cond_signal> will normally generate a warning if you attempt to use it
164 on an unlocked variable. On the rare occasions where doing this may be
165 sensible, you can skip the warning with
167 { no warnings 'threads'; cond_signal($foo) }
169 =item cond_broadcast VARIABLE
171 The C<cond_broadcast> function works similarly to C<cond_signal>.
172 C<cond_broadcast>, though, will unblock B<all> the threads that are blocked
173 in a C<cond_wait> on the locked variable, rather than only one.
179 threads::shared is designed to disable itself silently if threads are
180 not available. If you want access to threads, you must C<use threads>
181 before you C<use threads::shared>. threads will emit a warning if you
182 use it after threads::shared.
186 C<bless> is not supported on shared references. In the current version,
187 C<bless> will only bless the thread local reference and the blessing
188 will not propagate to the other threads. This is expected to be
189 implemented in a future version of Perl.
191 Does not support splice on arrays!
195 Arthur Bergman E<lt>arthur at contiller.seE<gt>
197 threads::shared is released under the same license as Perl
199 Documentation borrowed from Thread.pm
203 L<threads>, L<perlthrtut>