Commit | Line | Data |
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b050c948 | 1 | package threads::shared; |
73e09c8f | 2 | |
c46325ea | 3 | use 5.008; |
b050c948 AB |
4 | use strict; |
5 | use warnings; | |
5c360ac5 AB |
6 | BEGIN { |
7 | require Exporter; | |
8 | our @ISA = qw(Exporter); | |
a0e036c1 | 9 | our @EXPORT = qw(share cond_wait cond_timedwait cond_broadcast cond_signal); |
b162af07 | 10 | our $VERSION = '0.93'; |
73e09c8f | 11 | |
5c360ac5 | 12 | if ($threads::threads) { |
6f942b98 | 13 | *cond_wait = \&cond_wait_enabled; |
a0e036c1 | 14 | *cond_timedwait = \&cond_timedwait_enabled; |
6f942b98 AB |
15 | *cond_signal = \&cond_signal_enabled; |
16 | *cond_broadcast = \&cond_broadcast_enabled; | |
9c4972d9 NIS |
17 | require XSLoader; |
18 | XSLoader::load('threads::shared',$VERSION); | |
5c360ac5 AB |
19 | push @EXPORT,'bless'; |
20 | } | |
21 | else { | |
b050c948 | 22 | |
df5c998e EM |
23 | # String eval is generally evil, but we don't want these subs to exist at all |
24 | # if threads are loaded successfully. Vivifying them conditionally this way | |
25 | # saves on average about 4K of memory per thread. | |
b050c948 | 26 | |
df5c998e | 27 | eval <<'EOD'; |
a0e036c1 MP |
28 | sub cond_wait (\[$@%];\[$@%]) { undef } |
29 | sub cond_timedwait (\[$@%]$;\[$@%]) { undef } | |
30 | sub cond_signal (\[$@%]) { undef } | |
31 | sub cond_broadcast (\[$@%]) { undef } | |
32 | sub share (\[$@%]) { return $_[0] } | |
df5c998e EM |
33 | EOD |
34 | } | |
35 | } | |
b050c948 | 36 | |
dab065ea AB |
37 | $threads::shared::threads_shared = 1; |
38 | ||
6b85e4fe NIS |
39 | sub threads::shared::tie::SPLICE |
40 | { | |
41 | die "Splice not implemented for shared arrays"; | |
42 | } | |
43 | ||
b050c948 AB |
44 | __END__ |
45 | ||
46 | =head1 NAME | |
47 | ||
48 | threads::shared - Perl extension for sharing data structures between threads | |
49 | ||
50 | =head1 SYNOPSIS | |
51 | ||
73e09c8f | 52 | use threads; |
b050c948 AB |
53 | use threads::shared; |
54 | ||
38875929 DM |
55 | my $var : shared; |
56 | ||
4cab98c0 SG |
57 | my($scalar, @array, %hash); |
58 | share($scalar); | |
59 | share(@array); | |
aaf3876d | 60 | share(%hash); |
caf25f3b AB |
61 | my $bar = &share([]); |
62 | $hash{bar} = &share({}); | |
b050c948 | 63 | |
38875929 DM |
64 | { lock(%hash); ... } |
65 | ||
b050c948 | 66 | cond_wait($scalar); |
a0e036c1 | 67 | cond_timedwait($scalar, time() + 30); |
515f0976 AB |
68 | cond_broadcast(@array); |
69 | cond_signal(%hash); | |
b050c948 | 70 | |
a0e036c1 MP |
71 | my $lockvar : shared; |
72 | # condition var != lock var | |
73 | cond_wait($var, $lockvar); | |
74 | cond_timedwait($var, time()+30, $lockvar); | |
75 | ||
b050c948 AB |
76 | =head1 DESCRIPTION |
77 | ||
38875929 DM |
78 | By default, variables are private to each thread, and each newly created |
79 | thread gets a private copy of each existing variable. This module allows | |
32419a4c JH |
80 | you to share variables across different threads (and pseudoforks on Win32). |
81 | It is used together with the threads module. | |
b050c948 | 82 | |
515f0976 | 83 | =head1 EXPORT |
b050c948 | 84 | |
a0e036c1 | 85 | C<share>, C<cond_wait>, C<cond_timedwait>, C<cond_signal>, C<cond_broadcast> |
515f0976 | 86 | |
e67b86b3 | 87 | Note that if this module is imported when C<threads> has not yet been |
32419a4c JH |
88 | loaded, then these functions all become no-ops. This makes it possible |
89 | to write modules that will work in both threaded and non-threaded | |
e67b86b3 DM |
90 | environments. |
91 | ||
515f0976 AB |
92 | =head1 FUNCTIONS |
93 | ||
94 | =over 4 | |
95 | ||
96 | =item share VARIABLE | |
97 | ||
86c43dd6 JH |
98 | C<share> takes a value and marks it as shared. You can share a scalar, |
99 | array, hash, scalar ref, array ref or hash ref. C<share> will return | |
0a9af0ff | 100 | the shared rvalue but always as a reference. |
515f0976 AB |
101 | |
102 | C<share> will traverse up references exactly I<one> level. | |
103 | C<share(\$a)> is equivalent to C<share($a)>, while C<share(\\$a)> is not. | |
104 | ||
38875929 DM |
105 | A variable can also be marked as shared at compile time by using the |
106 | C<shared> attribute: C<my $var : shared>. | |
107 | ||
86c43dd6 JH |
108 | If you want to share a newly created reference unfortunately you |
109 | need to use C<&share([])> and C<&share({})> syntax due to problems | |
110 | with Perl's prototyping. | |
caf25f3b | 111 | |
515f0976 AB |
112 | =item lock VARIABLE |
113 | ||
32419a4c JH |
114 | C<lock> places a lock on a variable until the lock goes out of scope. |
115 | If the variable is locked by another thread, the C<lock> call will | |
116 | block until it's available. C<lock> is recursive, so multiple calls | |
117 | to C<lock> are safe -- the variable will remain locked until the | |
118 | outermost lock on the variable goes out of scope. | |
515f0976 | 119 | |
32419a4c JH |
120 | If a container object, such as a hash or array, is locked, all the |
121 | elements of that container are not locked. For example, if a thread | |
122 | does a C<lock @a>, any other thread doing a C<lock($a[12])> won't block. | |
515f0976 AB |
123 | |
124 | C<lock> will traverse up references exactly I<one> level. | |
125 | C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not. | |
126 | ||
32419a4c JH |
127 | Note that you cannot explicitly unlock a variable; you can only wait |
128 | for the lock to go out of scope. If you need more fine-grained | |
83272a45 | 129 | control, see L<Thread::Semaphore>. |
515f0976 AB |
130 | |
131 | =item cond_wait VARIABLE | |
132 | ||
a0e036c1 MP |
133 | =item cond_wait CONDVAR, LOCKVAR |
134 | ||
515f0976 | 135 | The C<cond_wait> function takes a B<locked> variable as a parameter, |
32419a4c JH |
136 | unlocks the variable, and blocks until another thread does a |
137 | C<cond_signal> or C<cond_broadcast> for that same locked variable. | |
138 | The variable that C<cond_wait> blocked on is relocked after the | |
139 | C<cond_wait> is satisfied. If there are multiple threads | |
140 | C<cond_wait>ing on the same variable, all but one will reblock waiting | |
141 | to reacquire the lock on the variable. (So if you're only using | |
142 | C<cond_wait> for synchronisation, give up the lock as soon as | |
143 | possible). The two actions of unlocking the variable and entering the | |
a0e036c1 | 144 | blocked wait state are atomic, the two actions of exiting from the |
38875929 | 145 | blocked wait state and relocking the variable are not. |
515f0976 | 146 | |
a0e036c1 MP |
147 | In its second form, C<cond_wait> takes a shared, B<unlocked> variable |
148 | followed by a shared, B<locked> variable. The second variable is | |
149 | unlocked and thread execution suspended until another thread signals | |
150 | the first variable. | |
151 | ||
32419a4c JH |
152 | It is important to note that the variable can be notified even if |
153 | no thread C<cond_signal> or C<cond_broadcast> on the variable. | |
154 | It is therefore important to check the value of the variable and | |
a0e036c1 MP |
155 | go back to waiting if the requirement is not fulfilled. For example, |
156 | to pause until a shared counter drops to zero: | |
157 | ||
158 | { lock($counter); cond_wait($count) until $counter == 0; } | |
159 | ||
160 | =item cond_timedwait VARIABLE, ABS_TIMEOUT | |
161 | ||
162 | =item cond_timedwait CONDVAR, ABS_TIMEOUT, LOCKVAR | |
163 | ||
164 | In its two-argument form, C<cond_timedwait> takes a B<locked> variable | |
165 | and an absolute timeout as parameters, unlocks the variable, and blocks | |
166 | until the timeout is reached or another thread signals the variable. A | |
167 | false value is returned if the timeout is reached, and a true value | |
168 | otherwise. In either case, the variable is re-locked upon return. | |
169 | ||
170 | Like C<cond_wait>, this function may take a shared, B<locked> variable | |
171 | as an additional parameter; in this case the first parameter is an | |
172 | B<unlocked> condition variable protected by a distinct lock variable. | |
173 | ||
174 | Again like C<cond_wait>, waking up and reacquiring the lock are not | |
175 | atomic, and you should always check your desired condition after this | |
176 | function returns. Since the timeout is an absolute value, however, it | |
177 | does not have to be recalculated with each pass: | |
178 | ||
179 | lock($var); | |
180 | my $abs = time() + 15; | |
181 | until ($ok = desired_condition($var)) { | |
182 | last if !cond_timedwait($var, $abs); | |
183 | } | |
184 | # we got it if $ok, otherwise we timed out! | |
515f0976 AB |
185 | |
186 | =item cond_signal VARIABLE | |
187 | ||
32419a4c JH |
188 | The C<cond_signal> function takes a B<locked> variable as a parameter |
189 | and unblocks one thread that's C<cond_wait>ing on that variable. If | |
190 | more than one thread is blocked in a C<cond_wait> on that variable, | |
191 | only one (and which one is indeterminate) will be unblocked. | |
515f0976 | 192 | |
32419a4c JH |
193 | If there are no threads blocked in a C<cond_wait> on the variable, |
194 | the signal is discarded. By always locking before signaling, you can | |
195 | (with care), avoid signaling before another thread has entered cond_wait(). | |
38875929 DM |
196 | |
197 | C<cond_signal> will normally generate a warning if you attempt to use it | |
198 | on an unlocked variable. On the rare occasions where doing this may be | |
199 | sensible, you can skip the warning with | |
200 | ||
201 | { no warnings 'threads'; cond_signal($foo) } | |
515f0976 AB |
202 | |
203 | =item cond_broadcast VARIABLE | |
204 | ||
205 | The C<cond_broadcast> function works similarly to C<cond_signal>. | |
32419a4c JH |
206 | C<cond_broadcast>, though, will unblock B<all> the threads that are |
207 | blocked in a C<cond_wait> on the locked variable, rather than only one. | |
b050c948 | 208 | |
4cab98c0 | 209 | =back |
dab065ea AB |
210 | |
211 | =head1 NOTES | |
212 | ||
8c5dce87 | 213 | threads::shared is designed to disable itself silently if threads are |
dab065ea AB |
214 | not available. If you want access to threads, you must C<use threads> |
215 | before you C<use threads::shared>. threads will emit a warning if you | |
8c5dce87 | 216 | use it after threads::shared. |
dab065ea | 217 | |
b050c948 AB |
218 | =head1 BUGS |
219 | ||
4cab98c0 | 220 | C<bless> is not supported on shared references. In the current version, |
515f0976 | 221 | C<bless> will only bless the thread local reference and the blessing |
4cab98c0 SG |
222 | will not propagate to the other threads. This is expected to be |
223 | implemented in a future version of Perl. | |
515f0976 | 224 | |
b050c948 | 225 | Does not support splice on arrays! |
b050c948 | 226 | |
58122748 JH |
227 | Taking references to the elements of shared arrays and hashes does not |
228 | autovivify the elements, and neither does slicing a shared array/hash | |
229 | over non-existent indices/keys autovivify the elements. | |
230 | ||
72ac79b3 SB |
231 | share() allows you to C<< share $hashref->{key} >> without giving any error |
232 | message. But the C<< $hashref->{key} >> is B<not> shared, causing the error | |
3d32476b | 233 | "locking can only be used on shared values" to occur when you attempt to |
72ac79b3 | 234 | C<< lock $hasref->{key} >>. |
3d32476b | 235 | |
b050c948 AB |
236 | =head1 AUTHOR |
237 | ||
aaf3876d | 238 | Arthur Bergman E<lt>arthur at contiller.seE<gt> |
b050c948 | 239 | |
aaf3876d | 240 | threads::shared is released under the same license as Perl |
b050c948 | 241 | |
5e549d84 | 242 | Documentation borrowed from the old Thread.pm |
515f0976 | 243 | |
b050c948 AB |
244 | =head1 SEE ALSO |
245 | ||
5e549d84 | 246 | L<threads>, L<perlthrtut>, L<http://www.perl.com/pub/a/2002/06/11/threads.html> |
b050c948 AB |
247 | |
248 | =cut |