1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro::Semaphore - non-binary semaphores |
3 | Coro::Semaphore - counting semaphores |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Coro::Semaphore; |
7 | use Coro; |
8 | |
8 | |
9 | $sig = new Coro::Semaphore [initial value]; |
9 | $sig = new Coro::Semaphore [initial value]; |
10 | |
10 | |
11 | $sig->down; # wait for signal |
11 | $sig->down; # wait for signal |
12 | |
12 | |
… | |
… | |
14 | |
14 | |
15 | $sig->up; |
15 | $sig->up; |
16 | |
16 | |
17 | =head1 DESCRIPTION |
17 | =head1 DESCRIPTION |
18 | |
18 | |
|
|
19 | This module implements counting semaphores. You can initialize a mutex |
|
|
20 | with any level of parallel users, that is, you can intialize a sempahore |
|
|
21 | that can be C<down>ed more than once until it blocks. There is no owner |
|
|
22 | associated with semaphores, so one thread can C<down> it while another |
|
|
23 | can C<up> it. |
|
|
24 | |
|
|
25 | Counting semaphores are typically used to coordinate access to |
|
|
26 | resources, with the semaphore count initialized to the number of free |
|
|
27 | resources. Threads then increment the count when resources are added |
|
|
28 | and decrement the count when resources are removed. |
|
|
29 | |
|
|
30 | You don't have to load C<Coro::Semaphore> manually, it will be loaded |
|
|
31 | automatically when you C<use Coro> and call the C<new> constructor. |
|
|
32 | |
19 | =over 4 |
33 | =over 4 |
20 | |
34 | |
21 | =cut |
35 | =cut |
22 | |
36 | |
23 | package Coro::Semaphore; |
37 | package Coro::Semaphore; |
24 | |
38 | |
|
|
39 | use common::sense; |
|
|
40 | |
25 | use Coro (); |
41 | use Coro (); |
26 | |
42 | |
27 | $VERSION = 0.09; |
43 | our $VERSION = 6.04; |
28 | |
44 | |
29 | =item new [inital count, default zero] |
45 | =item new [inital count] |
30 | |
46 | |
31 | Creates a new sempahore object with the given initial lock count. The |
47 | Creates a new sempahore object with the given initial lock count. The |
32 | default lock count is 1, which means it is unlocked by default. |
48 | default lock count is 1, which means it is unlocked by default. Zero (or |
|
|
49 | negative values) are also allowed, in which case the semaphore is locked |
|
|
50 | by default. |
33 | |
51 | |
34 | =cut |
52 | =item $sem->count |
35 | |
53 | |
36 | sub new { |
54 | Returns the current semaphore count. |
37 | bless [defined $_[1] ? $_[1] : 1], $_[0]; |
55 | |
38 | } |
56 | =item $sem->adjust ($diff) |
|
|
57 | |
|
|
58 | Atomically adds the amount given to the current semaphore count. If the |
|
|
59 | count becomes positive, wakes up any waiters. Does not block if the count |
|
|
60 | becomes negative, however. |
39 | |
61 | |
40 | =item $sem->down |
62 | =item $sem->down |
41 | |
63 | |
42 | Decrement the counter, therefore "locking" the semaphore. This method |
64 | Decrement the counter, therefore "locking" the semaphore. This method |
43 | waits until the semaphore is available if the counter is zero. |
65 | waits until the semaphore is available if the counter is zero. |
44 | |
66 | |
|
|
67 | =item $sem->wait |
|
|
68 | |
|
|
69 | Similar to C<down>, but does not actually decrement the counter. Instead, |
|
|
70 | when this function returns, a following call to C<down> or C<try> is |
|
|
71 | guaranteed to succeed without blocking, until the next thread switch |
|
|
72 | (C<cede> etc.). |
|
|
73 | |
|
|
74 | Note that using C<wait> is much less efficient than using C<down>, so try |
|
|
75 | to prefer C<down> whenever possible. |
|
|
76 | |
|
|
77 | =item $sem->wait ($callback) |
|
|
78 | |
|
|
79 | If you pass a callback argument to C<wait>, it will not wait, but |
|
|
80 | immediately return. The callback will be called as soon as the semaphore |
|
|
81 | becomes available (which might be instantly), and gets passed the |
|
|
82 | semaphore as first argument. |
|
|
83 | |
|
|
84 | The callback might C<down> the semaphore exactly once, might wake up other |
|
|
85 | threads, but is I<NOT> allowed to block (switch to other threads). |
|
|
86 | |
45 | =cut |
87 | =cut |
46 | |
88 | |
47 | sub down { |
89 | #=item $status = $sem->timed_down ($timeout) |
48 | my $self = shift; |
90 | # |
|
|
91 | #Like C<down>, but returns false if semaphore couldn't be acquired within |
|
|
92 | #$timeout seconds, otherwise true. |
|
|
93 | |
|
|
94 | #sub timed_down { |
|
|
95 | # require Coro::Timer; |
|
|
96 | # my $timeout = Coro::Timer::timeout ($_[1]); |
|
|
97 | # |
49 | while ($self->[0] <= 0) { |
98 | # while ($_[0][0] <= 0) { |
50 | push @{$self->[1]}, $Coro::current; |
99 | # push @{$_[0][1]}, $Coro::current; |
51 | Coro::schedule; |
100 | # &Coro::schedule; |
|
|
101 | # if ($timeout) { |
|
|
102 | # # ugly as hell. slow, too, btw! |
|
|
103 | # for (0..$#{$_[0][1]}) { |
|
|
104 | # if ($_[0][1][$_] == $Coro::current) { |
|
|
105 | # splice @{$_[0][1]}, $_, 1; |
|
|
106 | # return; |
|
|
107 | # } |
|
|
108 | # } |
|
|
109 | # die; |
|
|
110 | # } |
52 | } |
111 | # } |
53 | --$self->[0]; |
112 | # |
54 | } |
113 | # --$_[0][0]; |
|
|
114 | # return 1; |
|
|
115 | #} |
55 | |
116 | |
56 | =item $sem->up |
117 | =item $sem->up |
57 | |
118 | |
58 | Unlock the semaphore again. |
119 | Unlock the semaphore again. |
59 | |
|
|
60 | =cut |
|
|
61 | |
|
|
62 | sub up { |
|
|
63 | my $self = shift; |
|
|
64 | if (++$self->[0] > 0) { |
|
|
65 | (shift @{$self->[1]})->ready if @{$self->[1]}; |
|
|
66 | } |
|
|
67 | } |
|
|
68 | |
120 | |
69 | =item $sem->try |
121 | =item $sem->try |
70 | |
122 | |
71 | Try to C<down> the semaphore. Returns true when this was possible, |
123 | Try to C<down> the semaphore. Returns true when this was possible, |
72 | otherwise return false and leave the semaphore unchanged. |
124 | otherwise return false and leave the semaphore unchanged. |
73 | |
125 | |
|
|
126 | =item $sem->waiters |
|
|
127 | |
|
|
128 | In scalar context, returns the number of threads waiting for this |
|
|
129 | semaphore. |
|
|
130 | |
|
|
131 | =item $guard = $sem->guard |
|
|
132 | |
|
|
133 | This method calls C<down> and then creates a guard object. When the guard |
|
|
134 | object is destroyed it automatically calls C<up>. |
|
|
135 | |
74 | =cut |
136 | =cut |
75 | |
137 | |
76 | sub try { |
138 | sub guard { |
77 | my $self = shift; |
139 | &down; |
78 | if ($self->[0] > 0) { |
140 | bless [$_[0]], Coro::Semaphore::guard:: |
79 | --$self->[0]; |
|
|
80 | return 1; |
|
|
81 | } else { |
|
|
82 | return 0; |
|
|
83 | } |
|
|
84 | } |
141 | } |
85 | |
142 | |
86 | 1; |
143 | #=item $guard = $sem->timed_guard ($timeout) |
|
|
144 | # |
|
|
145 | #Like C<guard>, but returns undef if semaphore couldn't be acquired within |
|
|
146 | #$timeout seconds, otherwise the guard object. |
|
|
147 | |
|
|
148 | #sub timed_guard { |
|
|
149 | # &timed_down |
|
|
150 | # ? bless \\$_[0], Coro::Semaphore::guard:: |
|
|
151 | # : (); |
|
|
152 | #} |
|
|
153 | |
|
|
154 | sub Coro::Semaphore::guard::DESTROY { |
|
|
155 | &up($_[0][0]); |
|
|
156 | } |
87 | |
157 | |
88 | =back |
158 | =back |
89 | |
159 | |
90 | =head1 AUTHOR |
160 | =head1 AUTHOR |
91 | |
161 | |
92 | Marc Lehmann <pcg@goof.com> |
162 | Marc Lehmann <schmorp@schmorp.de> |
93 | http://www.goof.com/pcg/marc/ |
163 | http://home.schmorp.de/ |
94 | |
164 | |
95 | =cut |
165 | =cut |
96 | |
166 | |
|
|
167 | 1 |
|
|
168 | |