Re: [Boost-users] upgrading lock

Subject: Re: [Boost-users] upgrading lock
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-02-21 13:33:43

Le 21/02/13 14:05, Igor R a écrit :
> Hello,
>
> Just wanted to be sure that I'm doing this correctly.
>
> typedef boost::upgrade_lock<boost::shared_mutex> upgrade_lock;
> typedef boost::upgrade_to_unique_lock<boost::shared_mutex>
> upgrade_to_unique_lock;
>
> upgrade_lock readLock(mutex_);
> // accessing shared resources in read-only mode
> //...
> upgrade_to_unique_lock writeLock(readLock);
> // modifying shared resources
>
>
> Is the above correct? In particular, upgrade_lock acquires "read" lock
> in raii style (similarly to shared_lock), right?
>
>
>

Even if currently shared_mutex and upgrade_mutex implementation is the 
same you should use upgrade_mutex. Otherwise the code seems correct.
You have shared access in [1] and [2] and unique access in [2].

typedef boost::upgrade_lock<boost::upgrade_mutex> upgrade_lock;
typedef boost::upgrade_to_unique_lock<boost::upgrade_mutex> upgrade_to_unique_lock;

boost::upgrade_mutex mutex_;

{

   upgrade_lock readLock(mutex_);
   // [1] accessing shared resources in read-only mode
   //...
   {
     upgrade_to_unique_lock writeLock(readLock);
     // [2] modifying shared resources

}

   // [3] accessing shared resources in read-only mode

}

Best,
Vicente