Re: [PATCH] xenconsole: Ensure exclusive access to console using locks

From: Martin Lucina <martin@lucina.net>
To: Ian Jackson <Ian.Jackson@eu.citrix.com>
Cc: xen-devel@lists.xenproject.org, Wei Liu <wei.liu2@citrix.com>,
	Ian Campbell <ian.campbell@citrix.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH] xenconsole: Ensure exclusive access to console using locks
Date: Fri, 24 Jul 2015 15:42:22 +0200	[thread overview]
Message-ID: <20150724134222.GF25338@nodbug.lucina.net> (raw)
In-Reply-To: <21938.15968.711376.627272@mariner.uk.xensource.com>

On Friday, 24.07.2015 at 14:32, Ian Jackson wrote:
> > +static void console_lock(int domid)
> > +{
> > +	lockfile = malloc(PATH_MAX);
> > +	if (lockfile == NULL)
> > +		err(ENOMEM, "malloc");
> > +	snprintf(lockfile, PATH_MAX - 1, "%s/xenconsole.%d", XEN_LOCK_DIR, domid);
> 
> Why not use asprintf ?

asprintf is a GNU/BSD extension, not available on e.g. Solaris. Do we care
about that?

> You should use the same recipe as with-lock-ex (from chiark-utils)
> 
>   http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=chiark-utils.git;a=blob;f=cprogs/with-lock-ex.c;h=1850d1f0283bd61fc1da12458cba7ec0a227c572;hb=HEAD
>   
> (which we also use in tools/hotplug/Linux/locking.sh and
> tools/libxl/libxl_internal.c:libxl__lock_domain_userdata)

Thanks for the pointers, I'll use that strategy.

Martin