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: Wed, 29 Apr 2015 01:45:51 +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: Tue, 7 Apr 2015 13:03:14 +0200
 > 
 >  On Tue, Apr 07, 2015 at 01:55:01AM +0000, YAMAMOTO Takashi wrote:
 >  >  the intel's manual says:  (8.2.2)
 >  >  
 >  >      Reads may be reordered with older writes to different locations
 >  >      but not with older writes to the same location.
 >  >  
 >  >  see also 8.2.3.4 Example 8-3.
 >  >  
 >  >  isn't it the case for _rtld_exclusive_exit?
 >  
 >  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
 
 sorry for late reply.
 
 _rtld_exclusive_exit
     _rtld_mutex = 0;  // older write to different location
     waiter = _rtld_waiter_exclusive  // read
 
 my interpretation of the manual text is that these two accesses
 can be reordered.
 if it happens, _rtld_exclusive_enter can block on now unlocked mutex.
 
 YAMAMOTO Takashi