linux-kernel - Re: [PATCH 3/3] kref: Remove the memory barriers

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]

Date:	Mon, 12 Dec 2011 11:20:16 +0100
From:	Oliver Neukum <oneukum@...e.de>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, gregkh@...e.de,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	ostrikov@...dia.com, adobriyan@...il.com, eric.dumazet@...il.com,
	mingo@...e.hu
Subject: Re: [PATCH 3/3] kref: Remove the memory barriers

Am Montag, 12. Dezember 2011, 10:57:31 schrieb Ming Lei:
> On Mon, Dec 12, 2011 at 4:54 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Mon, 2011-12-12 at 11:48 +0800, Ming Lei wrote:
> >> For kref, maybe it is still multiple operations done on one cpu vs them
> >> being visible on another, but seems a bit implicit, see the common kref
> >> usage below:
> >>
> >> CPU0                            CPU1
> >>                                         A:kref_init(&obj->ref)
> >
> > how does CPU0 get a ref to obj?
> 
> Suppose open/close/read/.. context is run on CPU0, and driver .probe/.release
> context(hotplug context) is run on CPU1. There are a few examples on
> usb driver(eg. usb-skeleton.c, ...)

USB generally relies on an implied barrier just as:

        /* we can register the device now, as it is ready */
        retval = usb_register_dev(interface, &skel_class);

Generally reference counting cannot help you if kfree() is involved

	Regards
		Oliver
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/