Re: PR/49816 CVS commit: src/libexec/ld.elf_so

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

The following reply was made to PR lib/49816; it has been noted by GNATS.

From: Joerg Sonnenberger <joerg%britannica.bec.de@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: lib-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
	netbsd-bugs%netbsd.org@localhost, yamt%NetBSD.org@localhost
Subject: Re: PR/49816 CVS commit: src/libexec/ld.elf_so
Date: Wed, 8 Apr 2015 11:39:06 +0200

 On Wed, Apr 08, 2015 at 03:45:01AM +0000, Masao Uebayashi wrote:
 > The following reply was made to PR lib/49816; it has been noted by GNATS.
 > 
 > From: Masao Uebayashi <uebayasi%gmail.com@localhost>
 > To: gnats-bugs%netbsd.org@localhost
 > Cc: lib-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost, 
 > 	YAMAMOTO Takashi <yamt%netbsd.org@localhost>
 > Subject: Re: PR/49816 CVS commit: src/libexec/ld.elf_so
 > Date: Wed, 8 Apr 2015 12:42:28 +0900
 > 
 >  >  I don't think that's relevant, this is about global visiblity of
 >  >  changes. E.g. if another thread tries to get the mutex, it must see all
 >  >  changes from the current thread when successfully acquired the mutex.
 >  >
 >  >  Joerg
 >  
 >  I can't follow... Your first message was:
 
 The diff commited by yamt-san should not make any difference on
 architectures with Total Store Ordering, including x86, which he says he
 is running.
 
 >  > None of those should matter on amd64? CAS has an implicit total memory
 >  > barrier, so this seems to just add a lot of overhead for no reason.
 >  
 >  If you're talking about atomic vs. memory barrier, isn't it something
 >  addressed by the new C11 atomic API?  Kernel mutex code has
 >  MUTEX_RECEIVE()/MUTEX_GIVE() for that purpose (IIUC).
 
 Yes, except we don't have it available. I'm not sure if there even is
 support for it in gcc-4.8. For Clang, it would be just a question of
 installing stdatomic.h somewhere.
 
 Joerg