[boost] Re: boost::shared_ptr and atomic_count_linux.hpp

From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2002-05-31 08:50:45

Darin Adler wrote:
[...]
> Once we found this out, Peter Dimov and others changed smart_ptr 
> so that it doesn't use this header any more. They also made other 
> improvements to the thread safety code to make it simpler and faster. 
> The current version of Boost, 1.28.0, has this fixed.

Memory visibility (acquire-on-lock/release-on-unlock semantics) aside, 
the 'lwm' stuff in CVS (the one full of sched_yield()/winapi::Sleep(0)) 
is BROKEN... unless, of course, ALL boost MT client applications are 
meant for deployment on scheduling allocation domains of size ONE 
(uniprocessors) ONLY... WITH FIFO/RR priority scheduling {POSIX realtime 
option} among *ALL-EQUAL-PRTY* threads.

regards,
alexander.

P.S. "....Similarly, sched_yield() can be used to resolve some problems 
      on a uniprocessor, though such problems can usually be solved more 
      cleanly in other ways. Using sched_yield() will never solve a
problem 
      (unless the problem statement is "the performance is too good") on
a 
      multiprocessor, and you should never use it there."
--Butenhof_at_c.p.t