linux-kernel - Re: contention on long-held spinlock

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Message-Id: <201108231824.48512.arnd@arndb.de>
Date:	Tue, 23 Aug 2011 18:24:48 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Bryan Donlan <bdonlan@...il.com>
Cc:	Ortwin Glück <odi@....ch>,
	linux-kernel@...r.kernel.org,
	Andrew Vasquez <andrew.vasquez@...gic.com>,
	linux-driver@...gic.com, linux-scsi@...r.kernel.org
Subject: Re: contention on long-held spinlock

On Friday 19 August 2011, Bryan Donlan wrote:
> That's what mutexes are for. Note, however, that interrupt handlers
> cannot use mutexes as they cannot sleep, nor can they wait for lock
> holders which may themselves sleep.

I agree that there is probably some other bug that needs to be fixed
in the driver, but for testing it may well be worth replacing
the spinlock with a mutex and the request_irq with request_threaded_irq.
A threaded IRQ is slower than a normal one but does allow mutexes.

	Arnd
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