Re: [Threads-devel] shared mutex locking discipline

From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2008-04-14 10:09:07

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On Monday 14 April 2008 03:40 am, Anthony Williams wrote:
> sides, as you point out. This only happens if you start with an
> upgrade_lock on A, since otherwise you have to unlock the shared lock
> before you can take the unique lock, and taking an upgrade lock should

I don't think that is true, since you can smoothly transition from a 
shared_lock to an upgrade_lock.  It's true upgrade_lock doesn't support 
moving a shared_lock into an upgrade lock, but you can transition from a 
shared to upgrade lock by doing:

mutex_type m;
shared_lock<mutex_type> shared(m);
upgrade_lock<mutex_type> upgrade(m);
shared.unlock();

- -- 
Frank
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