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
| ||
|
Date: Sat, 14 Apr 2012 22:27:08 +0200 From: Oleg Nesterov <oleg@...hat.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Andrew Morton <akpm@...ux-foundation.org>, David Howells <dhowells@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Alexander Gordeev <agordeev@...hat.com>, Chris Zankel <chris@...kel.net>, David Smith <dsmith@...hat.com>, "Frank Ch. Eigler" <fche@...hat.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, Larry Woodman <lwoodman@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v4 1/3] task_work_add: generic process-context callbacks On 04/14, Linus Torvalds wrote: > > On Fri, Apr 13, 2012 at 8:39 PM, Oleg Nesterov <oleg@...hat.com> wrote: > >> > > Once the caller does task_work_add(twork), it no longer "owns" this > > twork. > > > > But, if task_work_cancel() succeeds - you own it again. > > *IF* it succeeds. Sure. > >> But then you can't allocate it on the stack any more, and have to > >> allocate it separately. > > > > Yes, unless you do task_work_add/cancel(current). > > Ok, your argument seems to be that "current" is special, and can not > race, because the work execution is always synchronous with the task > it got scheduled on. Yes, exactly. > And that whole "run_task_work()" function should *not* take a "task" > pointer, because it would be horribly horribly wrong to ever run it in > any context than "current". And it was task_work_queue(void) initially. But then I decided to micro-optimize this, the callers already have this task_struct in the register. And we have other examples like this, say, exit_mm(). However. I agree that it would be more understandable and clean to use current in task_work_run(void), and percpu_read is cheap. So I'll remove this argument and send v5 after David reviews 3/3. Oleg. -- 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/
Powered by blists - more mailing lists