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

[yamt%netbsd.org@localhost (YAMAMOTO Takashi)]

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

From: yamt%netbsd.org@localhost (YAMAMOTO Takashi)
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: Mon,  6 Apr 2015 16:09:29 +0000 (UTC)

 > 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: 
 > Subject: Re: PR/49816 CVS commit: src/libexec/ld.elf_so
 > Date: Mon, 6 Apr 2015 13:33:30 +0200
 > 
 >  On Mon, Apr 06, 2015 at 09:35:00AM +0000, YAMAMOTO Takashi wrote:
 >  >  Log Message:
 >  >  Fix membars around rtld internal mutex.
 >  >  
 >  >  This fixes the most of lockups i observed with Open vSwitch
 >  >  on NetBSD/amd64.  ("most of" because it still occasionally
 >  >  locks up because of other problems.  see PR/49816)
 >  
 >  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.
 
 except that:
 * _rtld_exclusive_exit doesn't use CAS
 * this code is MI
 
 i agree that something like PTHREAD__ATOMIC_IS_MEMBAR
 would be a nice optimization, though.
 
 YAMAMOTO Takashi
 
 >  
 >  Joerg