From: Matthias Kaehlcke <matthias-RprLehDfhQ3k1uMJSBkQmQ@public.gmane.org>
To: NiTr0 <nitr0-z9XQkeP78BxUq1AO9QMCaQ@public.gmane.org>
Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: i2c_smbus_write_block_data vs scheduled routine calls (add_timer) - kernel crash
Date: Tue, 4 Aug 2009 21:45:07 +0200 [thread overview]
Message-ID: <20090804194506.GA30151@darwin> (raw)
In-Reply-To: <4A788121.8020601-z9XQkeP78BxUq1AO9QMCaQ@public.gmane.org>
El Tue, Aug 04, 2009 at 09:42:41PM +0300 NiTr0 ha dit:
> I tried to improve voltage/FSB manipulation module for EeePC
> (http://code.google.com/p/eeepc-linux) - and I found that
> i2c_smbus_write_block_data will cause kernel panic when is called from
> function called by timer. I can't see kernel panic message because
> system print very long call trace. Also on EeePC there is no RS232 port
> - but I have USB->RS232 dongle, can it be used as terminal for debug
> messages?
>
> All variables are declared as static, all data is prepared correctly -
> so IMHO trouble is outside of my driver.
> There is a part of code:
>
> static struct i2c_client eee_pll_smbus_client = {
> .adapter = NULL,
> .addr = 0x69,
> .flags = 0,
> };
> static char eee_pll_data[I2C_SMBUS_BLOCK_MAX];
> static int eee_pll_datalen = 0;
> .......................
> i2c_smbus_write_block_data(&eee_pll_smbus_client,0,
> eee_pll_datalen, eee_pll_data);
a possible source of problems is that i2c_smbus_xfer() (invoked by
i2c_smbus_write_block_data()) tries to aquire a mutex if
adapter->algo->smbus_xfer is set.
http://lxr.linux.no/linux+v2.6.30/drivers/i2c/i2c-core.c#L1994
timers are executed in a softirq, ie in interrupt context, but mutexes
must not be used within interrupts.
i'm neither an i2c-core nor an kernel expert, but this point looks
conflictive to me and might be the reason for the kernel panic you
get.
--
Matthias Kaehlcke
Embedded Linux Engineer
Barcelona
They that can give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety
(Benjamin Franklin)
.''`.
using free software / Debian GNU/Linux | http://debian.org : :' :
`. `'`
gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-
next prev parent reply other threads:[~2009-08-04 19:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-04 18:42 i2c_smbus_write_block_data vs scheduled routine calls (add_timer) - kernel crash NiTr0
[not found] ` <4A788121.8020601-z9XQkeP78BxUq1AO9QMCaQ@public.gmane.org>
2009-08-04 19:45 ` Matthias Kaehlcke [this message]
2009-08-04 20:35 ` Mark Brown
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20090804194506.GA30151@darwin \
--to=matthias-rprlehdfhq3k1umjsbkqmq@public.gmane.org \
--cc=linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=nitr0-z9XQkeP78BxUq1AO9QMCaQ@public.gmane.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox