linux-kernel - Re: tty breakage in X (Was: tty vs workqueue oddities)

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Message-ID: <1307096592_10534@mail4.comsite.net>
Date:	Fri, 03 Jun 2011 05:23:12 -0500
From:	Milton Miller <miltonm@....com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	<linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Stefan Bigler <stefan.bigler@...mile.com>,
	Toby Gray <toby.gray@...lvnc.com>, Felipe Balbi <balbi@...com>
Subject: Re: tty breakage in X (Was: tty vs workqueue oddities)

[not on list so made up cc list]

On Fri Jun 03 2011 about 05:37:52 EST, Linus wrote:
> On Fri, Jun 3, 2011 at 3:56 PM, Benjamin Herrenschmidt wrote:
> > So I think my theory stands that flush_to_ldisc constantly reschedule
> > itself causing the worker thread to eat all CPU and starve the consumer
> > of the PTY. I won't have time to dig much deeper today nor probably this
> > week-end so I'm sending this email for others who want to look.
> 
> Gaah - that commit is total and utter crap.
> 
> I *removed* the whole "reschedule the work queue again" crap. It was
> totally wrong. See commit a5660b41af6a.
> 
> But then commit b1c43f82c5aa added the crap right back in.
> 
> So does it all work if you just remove the broken schedule_work() line
> from flush_to_ldisc?
> 
> Otherwise we'll need to just revert it. The commit is clearly totally broken.

Its further broken in that the recieve_buf functions return -ERRORS
but the callers don't check for negative values.

milton
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