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Viewing changes to system/lib/libcxx/shared_mutex.cpp

  • Committer: Package Import Robot
  • Author(s): Sylvestre Ledru
  • Date: 2014-01-19 14:12:40 UTC
  • mfrom: (4.1.2 sid)
  • Revision ID: package-import@ubuntu.com-20140119141240-nfiw0p8033oitpfz
Tags: 1.9.0~20140119~7dc8c2f-1
http://bugs.debian.org/733714
http://bugs.debian.org/735903
* New snapshot release (Closes: #733714)
* Provide sources for javascript and flash. Done in orig-tar.sh
  Available in third_party/websockify/include/web-socket-js/src/
  (Closes: #735903)

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system/lib/libcxx/shared_mutex.cpp
 
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//===---------------------- shared_mutex.cpp ------------------------------===//
 
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//
 
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//                     The LLVM Compiler Infrastructure
 
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//
 
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// This file is dual licensed under the MIT and the University of Illinois Open
 
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// Source Licenses. See LICENSE.TXT for details.
 
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//
 
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//===----------------------------------------------------------------------===//
 
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#define _LIBCPP_BUILDING_SHARED_MUTEX
 
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#include "shared_mutex"
 
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_LIBCPP_BEGIN_NAMESPACE_STD
 
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shared_mutex::shared_mutex()
 
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    : __state_(0)
 
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{
 
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}
 
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// Exclusive ownership
 
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void
 
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shared_mutex::lock()
 
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{
 
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    unique_lock<mutex> lk(__mut_);
 
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    while (__state_ & __write_entered_)
 
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        __gate1_.wait(lk);
 
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    __state_ |= __write_entered_;
 
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    while (__state_ & __n_readers_)
 
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        __gate2_.wait(lk);
 
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}
 
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bool
 
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shared_mutex::try_lock()
 
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{
 
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    unique_lock<mutex> lk(__mut_);
 
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    if (__state_ == 0)
 
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    {
 
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        __state_ = __write_entered_;
 
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        return true;
 
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    }
 
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    return false;
 
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}
 
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void
 
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shared_mutex::unlock()
 
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{
 
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    lock_guard<mutex> _(__mut_);
 
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    __state_ = 0;
 
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    __gate1_.notify_all();
 
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}
 
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// Shared ownership
 
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void
 
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shared_mutex::lock_shared()
 
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{
 
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    unique_lock<mutex> lk(__mut_);
 
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    while ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
 
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        __gate1_.wait(lk);
 
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    unsigned num_readers = (__state_ & __n_readers_) + 1;
 
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    __state_ &= ~__n_readers_;
 
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    __state_ |= num_readers;
 
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}
 
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bool
 
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shared_mutex::try_lock_shared()
 
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{
 
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    unique_lock<mutex> lk(__mut_);
 
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    unsigned num_readers = __state_ & __n_readers_;
 
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    if (!(__state_ & __write_entered_) && num_readers != __n_readers_)
 
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    {
 
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        ++num_readers;
 
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        __state_ &= ~__n_readers_;
 
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        __state_ |= num_readers;
 
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        return true;
 
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    }
 
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    return false;
 
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}
 
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void
 
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shared_mutex::unlock_shared()
 
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{
 
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    lock_guard<mutex> _(__mut_);
 
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    unsigned num_readers = (__state_ & __n_readers_) - 1;
 
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    __state_ &= ~__n_readers_;
 
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    __state_ |= num_readers;
 
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    if (__state_ & __write_entered_)
 
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    {
 
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        if (num_readers == 0)
 
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            __gate2_.notify_one();
 
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    }
 
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    else
 
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    {
 
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        if (num_readers == __n_readers_ - 1)
 
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            __gate1_.notify_one();
 
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    }
 
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}
 
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_LIBCPP_END_NAMESPACE_STD