linux-kernel - Re: SDHCI: mdelay() in hot path in esdhc_pltfm_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20150708064304.GB18700@pengutronix.de>
Date:	Wed, 8 Jul 2015 08:43:04 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Holger Schurig <holgerschurig@...il.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Fabio Estevam <festevam@...il.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Chris Ball <chris@...ntf.net>,
	open list <linux-kernel@...r.kernel.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Dong Aisheng <b29396@...escale.com>
Subject: Re: SDHCI: mdelay() in hot path in esdhc_pltfm_set_clock looses CAN
 (!) frames

On Wed, Jul 08, 2015 at 08:22:57AM +0200, Holger Schurig wrote:
> Wow, at last some reaction. And I thought nobody cares ...
> 
> BTW, removing CONFIG_MMC_CLKGATE helped a bit, because the pointless
> clock-off-clock-on while the device is booting (or accessing multiple
> sectors within a short time) isn't going to happen anymore.
> 
> But really, a mdelay(1) in a driver ...

Look for the other mdelays in sdhci.c. There are up to a hundred of
them in sdhci_reset() which is called under a spin_lock_irqsave. I
remember that with the wrong type of card detection the MMC core
frequently polls for a card and if none is found the sdhci core was
resetted which falls into this mdelay polling loop in sdhci_reset. So if
you care about realtime you better have a card inserted...

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/