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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Andrew Bird <ajb@spheresystems.co.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Spinlock debugging
Date: Mon, 11 Sep 2006 18:24:52 +0100	[thread overview]
Message-ID: <1157995492.23085.191.camel@localhost.localdomain> (raw)
In-Reply-To: <200609111738.21818.ajb@spheresystems.co.uk>

Ar Llu, 2006-09-11 am 17:38 +0100, ysgrifennodd Andrew Bird:
> Alan
> 	Yes, I have low_latency set for kernels lower than 2.6.17. I'm currently 
> testing using 2.6.15. When you mention 'write method for flow control' do you 
> mean for software XON/XOFF etc?

Yes

Basically in low_latency the following is valid


	driver receives bytes
		flush_to_ldisc
			ldisc calls driver write methods


That means if you have a shared lock for read/write you want to drop it
after you've bashed the hardware and before you flush_to_ldisc. Remember
the IRQ handler is not re-entrant so another IRQ of the same number
won't cause further I/O and out of order receives.

Alan


  reply	other threads:[~2006-09-11 17:01 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-09-11 15:32 Andrew Bird (Sphere Systems)
2006-09-11 16:36 ` Alan Cox
2006-09-11 16:38   ` Andrew Bird
2006-09-11 17:24     ` Alan Cox [this message]
2006-09-12  7:47       ` Andrew Bird
2006-09-12 13:43         ` Alan Cox
2006-09-12 13:31           ` Sergei Organov
2006-09-12 14:04             ` Alan Cox

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