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Re: [patch] Make std::tr1::shared_ptr thread-safe.

From: "Peter Dimov" <pdimov at mmltd dot net>
To: "Jakub Jelinek" <jakub at redhat dot com>,"Ulrich Drepper" <drepper at redhat dot com>
Cc: "Jonathan Wakely" <cow at compsoc dot man dot ac dot uk>,<libstdc++ at gcc dot gnu dot org>,<gcc-patches at gcc dot gnu dot org>,"Alexander Terekhov" <TEREKHOV at de dot ibm dot com>
Date: Wed, 30 Mar 2005 21:58:31 +0300
Subject: Re: [patch] Make std::tr1::shared_ptr thread-safe.
References: <20050329130005.GA58022@compsoc.man.ac.uk> <424AE74A.7020400@redhat.com> <20050330180859.GP17420@devserv.devel.redhat.com>

Jakub Jelinek wrote:

Even as an interim solution it sounds wrong.  The lock has been added
to this method only, so it would only protect from concurent
add_ref_lock calls.  But _M_use_count is changed in a bunch of other
methods as well, so either you use atomic instructions everywhere, or
you use (the same) lock everywhere, but mixing that just can't work.

It is correct, to the best of my knowledge. This is Tyson Whitehead's CASless modification of the original CASful algorithm by Alexander Terekhov.

http://lists.boost.org/MailArchives/boost/msg66868.php

References:
- [patch] Make std::tr1::shared_ptr thread-safe.
  - From: Jonathan Wakely
- Re: [patch] Make std::tr1::shared_ptr thread-safe.
  - From: Ulrich Drepper
- Re: [patch] Make std::tr1::shared_ptr thread-safe.
  - From: Jakub Jelinek

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