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Date: Wed, 2 Jan 2013 12:13:05 -0800
Message-ID: <CAJ-VmomkzNgSyicAwcj_TWg24v-DH+Q7U6ifXFFognx-7nEZvw@mail.gmail.com> (sfid-20130102_211311_413909_64D6B932)
Subject: Re: [RFC] ATH9K: infinite loop in Tasklet
From: Adrian Chadd <adrian@freebsd.org>
To: voncken <cedric.voncken@acksys.fr>
Cc: Felix Fietkau <nbd@openwrt.org>,
	Mohammed Shafi <shafi.wireless@gmail.com>,
	linux-wireless@vger.kernel.org
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Sender: linux-wireless-owner@vger.kernel.org

On 2 January 2013 09:15, voncken <cedric.voncken@acksys.fr> wrote:
>         Yes,
>
>         I used an mpc8314 at 400Mhz, with 128 Mbit of RAM for my test.

Ah!

>         To find it, I measured the time elapsing in ath_rxbuf_alloc(..) with
> the kernel function local_clock().
>
>         With SLOB I found around 123 us (and I have an infinite loop in
> ath9k tasklet, because when I have consumed one packet the next packet is
> ready to rx process)
>         With SLAB I found around 22 us
>         With SLUB I found around 10 us

Cool. That's significantly more CPU.. :-)

So yes, the right thing to do here is to break out after a limit is
reached, and if we hit that limit, re-schedule that tasklet to run.


Adrian