linux-kernel - Re: [PATCH] task_work: remove fifo ordering guarantee

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Date:	Sat, 29 Aug 2015 11:22:19 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH] task_work: remove fifo ordering guarantee


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Fri, Aug 28, 2015 at 7:42 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> >
> > We could add yet another cond_resched() in the reverse loop, or we can simply 
> > remove the reversal, as I do not think anything would depend on order of 
> > task_work_add() submitted works.
> 
> So I think this should be ok, with things like file closing not really caring 
> about ordering as far as I can tell.
> 
> However, has anybody gone through all the task-work users? I looked quickly at 
> the task_work_add() cases, and didn't see anything that looked like it would 
> care, but others should look too. In the vfs, theres' the delayed fput and mnt 
> freeing, and there's a keyring installation one.
> 
> The threaded irq handlers use it as that exit-time hack, which certainly 
> shouldn't care, and there's some uprobe thing.
> 
> Can anybody see anything fishy?

So I'm wondering, is there any strong reason why we couldn't use a double linked 
list and still do FIFO and remove that silly linear list walking hack?

Thanks,

	Ingo
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