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: 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