From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Peter Hurley <peter@hurleysoftware.com>,
Eric Dumazet <edumazet@google.com>
Cc: David Miller <davem@davemloft.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
Greg KH <gregkh@linuxfoundation.org>,
dmaengine@vger.kernel.org,
John Ogness <john.ogness@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: Softirq priority inversion from "softirq: reduce latencies"
Date: Mon, 7 Mar 2016 16:48:14 +0100 [thread overview]
Message-ID: <56DDA2BE.7050800@linutronix.de> (raw)
In-Reply-To: <56D1E8B6.6090003@hurleysoftware.com>
On 02/27/2016 07:19 PM, Peter Hurley wrote:
> Hi Eric,
Hi Peter,
> Because both the uart driver (omap8250) and the dmaengine driver
> (edma) were (relatively) new, we assumed there was some race between
> starting a new rx DMA and processing the previous one.
Now after digesting the whole thread. I complained about this a long
while ago. After you start RX-DMA the DMA-engine is not programmed
immediately but deferred into softirq/tasklet. This is not the case for
continuous DMA transfer - those are programmed right away.
I don't remember that I found a reason why this simple programming has
to be deferred and can't happen immediately like it is the case for the
continuous DMA transfers. So I skipped that. RX-DMA in UART was working
well but for some reason omap's MMC-card driver refused to work.
Sebastian
prev parent reply other threads:[~2016-03-07 15:48 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-27 18:19 Softirq priority inversion from "softirq: reduce latencies" Peter Hurley
2016-02-27 20:13 ` Eric Dumazet
2016-02-27 20:29 ` Peter Hurley
2016-02-27 23:04 ` David Miller
2016-02-27 23:33 ` Peter Hurley
2016-02-28 1:59 ` Eric Dumazet
2016-02-28 2:10 ` Peter Hurley
2016-02-28 2:17 ` Eric Dumazet
2016-02-28 4:46 ` David Miller
2016-02-28 5:55 ` Mike Galbraith
2016-02-28 17:01 ` Francois Romieu
2016-02-29 4:58 ` Mike Galbraith
2016-02-29 15:03 ` Peter Hurley
2016-02-29 15:19 ` Eric Dumazet
2016-02-29 15:54 ` Peter Hurley
2016-02-29 16:21 ` Eric Dumazet
2016-02-29 18:05 ` Peter Hurley
2016-02-29 18:24 ` Eric Dumazet
2016-02-29 18:53 ` Peter Hurley
2016-02-29 19:14 ` Thomas Gleixner
2016-02-29 20:24 ` David Miller
2016-02-29 23:04 ` Peter Hurley
2016-02-29 15:27 ` Eric Dumazet
2016-02-29 19:13 ` Peter Hurley
2016-02-29 19:43 ` Eric Dumazet
2016-02-29 15:40 ` Mike Galbraith
2016-02-29 15:58 ` Peter Hurley
2016-02-29 16:24 ` Eric Dumazet
2016-02-29 17:16 ` David Miller
2016-03-07 15:31 ` Sebastian Andrzej Siewior
2016-03-07 17:06 ` Mike Galbraith
2016-03-07 15:48 ` Sebastian Andrzej Siewior [this message]
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