linux-kernel - Re: [Xen-devel] [PATCH v2 09/13] xen/pvcalls: implement recvmsg

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.10.1707261703180.22381@sstabellini-ThinkPad-X260>
Date:   Wed, 26 Jul 2017 17:08:36 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, jgross@...e.com,
        Stefano Stabellini <stefano@...reto.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH v2 09/13] xen/pvcalls: implement recvmsg

On Wed, 26 Jul 2017, Boris Ostrovsky wrote:
> >> +			count++;
> >> +		else
> >> +			wait_event_interruptible(map->active.inflight_conn_req,
> >> +						 pvcalls_front_read_todo(map));
> >> +	}
> > Should we be using PVCALLS_FRONT_MAX_SPIN here? In sendmsg it is
> > counting non-sleeping iterations but here we are sleeping so
> > PVCALLS_FRONT_MAX_SPIN (5000) may take a while.
> >
> > In fact, what shouldn't this waiting be a function of MSG_DONTWAIT
> 
> err, which it already is. But the question still stands (except for
> MSG_DONTWAIT).

The code (admittedly unintuitive) is busy-looping (non-sleeping) for
5000 iterations *before* attempting to sleep. So in that regard, recvmsg
and sendmsg use PVCALLS_FRONT_MAX_SPIN in the same way: only for
non-sleeping iterations.