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=head1 NAME |
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|
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Coro::RWLock - reader/write locks |
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|
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=head1 SYNOPSIS |
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|
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use Coro::RWLock; |
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|
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$lck = new Coro::RWLock; |
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|
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$lck->rdlock; # acquire read lock |
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|
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$lck->unlock; |
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|
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=head1 DESCRIPTION |
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|
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This module implements reader/write locks. A read can be acquired for |
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read by many coroutines in parallel as long as no writer has locked it |
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(shared access). A single write lock can be acquired when no readers |
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exist. RWLocks basically allow many concurrent readers (without writers) |
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OR a single writer (but no readers). |
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|
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=over 4 |
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|
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=cut |
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|
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package Coro::RWLock; |
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|
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BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") } |
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|
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use Coro (); |
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|
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$VERSION = 1.9; |
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|
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=item $l = new Coro::RWLock; |
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|
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Create a new reader/writer lock. |
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|
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=cut |
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|
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sub new { |
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# [rdcount, [readqueue], wrcount, [writequeue]] |
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bless [0, [], 0, []], $_[0]; |
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} |
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|
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=item $l->rdlock |
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|
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Acquire a read lock. |
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|
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=item $l->tryrdlock |
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|
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Try to acquire a read lock. |
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|
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=cut |
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|
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sub rdlock { |
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while ($_[0][0]) { |
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push @{$_[0][3]}, $Coro::current; |
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Coro::schedule; |
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} |
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++$_[0][2]; |
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} |
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|
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sub tryrdlock { |
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return if $_[0][0]; |
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++$_[0][2]; |
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} |
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|
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=item $l->wrlock |
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Acquire a write lock. |
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|
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=item $l->trywrlock |
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|
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Try to acquire a write lock. |
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|
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=cut |
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|
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sub wrlock { |
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while ($_[0][0] || $_[0][2]) { |
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push @{$_[0][1]}, $Coro::current; |
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Coro::schedule; |
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} |
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++$_[0][0]; |
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} |
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|
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sub trywrlock { |
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return if $_[0][0] || $_[0][2]; |
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++$_[0][0]; |
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} |
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|
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=item $l->unlock |
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|
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Give up the rwlock. |
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|
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=cut |
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|
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sub unlock { |
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# either we are a reader or a writer. decrement accordingly. |
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if ($_[0][2]) { |
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return if --$_[0][2]; |
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} else { |
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$_[0][0]--; |
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} |
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# now we have the choice between waking up a reader or a writer. we choose the writer. |
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if (@{$_[0][1]}) { |
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(shift @{$_[0][1]})->ready; |
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} elsif (@{$_[0][3]}) { |
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(shift @{$_[0][3]})->ready; |
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} |
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} |
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|
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1; |
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|
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=back |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de/ |
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|
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=cut |
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