[pacman-dev] [PATCH 1/1] alpm: use flock() for db lock

[Christian Hesse]

Allan McRae <allan at archlinux.org> on Wed, 2017/06/07 08:06:
> On 07/06/17 07:56, Christian Hesse wrote:
> > Allan McRae <allan at archlinux.org> on Wed, 2017/06/07 07:37:  
> >> On 07/06/17 07:26, Christian Hesse wrote:  
> >>> From: Christian Hesse <mail at eworm.de>
> >>>
> >>> We used to check for file existens, but that suffers from stale lock
> >>> files caused by unexpected events like crash, shutdown, etc.
> >>>
> >>> Instead use flock() to lock the file. It does not matter whether or
> >>> not the file exists but whether an exclusive lock can be obtained.
> >>>
> >>> Also remove the hint about removing the file from pacman.    
> >>
> >> This does not work with NFS filesystems.  
> > 
> > Uh, did not know NFS has issues here. However, this is from NFS FAQ [0]:
> >   
> >> The NFS client in 2.6.12 provides support for flock()/BSD locks on NFS
> >> files by emulating the BSD-style locks in terms of POSIX byte range
> >> locks. Other NFS clients that use the same emulation mechanism, or that
> >> use fcntl()/POSIX locks, will then see the same locks that the Linux NFS
> >> client sees.  
> > 
> > Given the fact that linux 2.6.12 has been released nearly twelve years
> > ago... We still do not want to use this?
> > 
> > Does any other locking mechanism has a chance to be accepted?
> > 
> > [0] http://nfs.sourceforge.net/#faq_d10
> >   
> 
> Bringing back on list.
> 
> We has issues with NFS/OSX last time this was run (need to look up last
> time this was discussed).  I think out support for OSX is dead, so we
> could ignore that...
> 
> I would not mind flock being used to lock individual files, but leaving
> an overall lock file during a transaction is useful.

Andrew provided a link. ;)

There are some valid arguments against flock()... So yes, let's keep things
as-is. :-p
-- 
main(a){char*c=/*    Schoene Gruesse                         */"B?IJj;MEH"
"CX:;",b;for(a/*    Best regards             my address:    */=0;b=c[a++];)
putchar(b-1/(/*    Chris            cc -ox -xc - && ./x    */b/42*2-3)*42);}
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