Date: Wed, 7 Aug 2013 23:16:36 -0600 From: Warner Losh <imp@bsdimp.com> To: Adrian Chadd <adrian@FreeBSD.org> Cc: current@freebsd.org, Bryan Venteicher <bryanv@daemoninthecloset.org>, Navdeep Parhar <np@freebsd.org>, net@freebsd.org, Giuseppe Lettieri <g.lettieri@iet.unipi.it>, Luigi Rizzo <rizzo@iet.unipi.it> Subject: Re: [net] protecting interfaces from races between control and data ? Message-ID: <CCB7CD35-4D48-449B-8DFE-FC63F7F26ED9@bsdimp.com> In-Reply-To: <CAJ-Vmomd9bD9cXJtOWnuL_yuM%2BF%2Bt6zaaEgq2PxiT_wxQi%2Bejg@mail.gmail.com> References: <20130805082307.GA35162@onelab2.iet.unipi.it> <2034715395.855.1375714772487.JavaMail.root@daemoninthecloset.org> <CAJ-VmokT6YKPR7CXsoCavEmWv3W8urZu4eBVgKWaj9iMaVJFZg@mail.gmail.com> <CA%2BhQ2%2BhuoCCweq7fjoYmH3nyhmhb5DzukEdPSMtaJEWa8Ft0JQ@mail.gmail.com> <51FFDD1E.1000206@FreeBSD.org> <CAJ-Vmo=Q9AqdBJ0%2B4AiX4%2BWreYuZx6VGGYw=MZ4XhMB1P2yMww@mail.gmail.com> <CAJ-Vmomd9bD9cXJtOWnuL_yuM%2BF%2Bt6zaaEgq2PxiT_wxQi%2Bejg@mail.gmail.com>
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On Aug 5, 2013, at 11:20 AM, Adrian Chadd wrote: > .. and I bet it's not a design pattern, and this is total conjecture = on my part: >=20 > * the original drivers weren't SMP safe; > * noone really sat down and figured out how to correctly synchronise > all of this stuff; > * people did the minimum amount of work to keep the driver from > immediately crashing, but didn't really think things through at a > larger scale. >=20 > Almost every driver is this way Luigi. :-) Most of the drivers in the three don't support hardware that performs = well enough for this to be a problem. :) Any driver that's still around = from the pre-locking days can easily saturate the lines (or the = hardware) on today's (and even yesterday's hardware). All the rest have come up with different ways to cope... Warner
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