From: Bing Zhao <bzhao@marvell.com>
To: Daniel Drake <dsd@laptop.org>
CC: "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Date: Thu, 21 Feb 2013 11:57:02 -0800
Subject: RE: mwifiex crash when removing interface while scanning
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Hi Daniel,

> > That's strange.
> > "mwifiex_sdio mmc0:0001:1: rx_pending=0, tx_pending=0, cmd_pending=-1" is from
> > mwifiex_remove_card().
> 
> I haven't dug into the code, but it seems quite normal to me. It makes
> sense for mwifiex_remove_card to be called in the rmmod path. And it

Ah, you are right. I overlooked that rmmod will lead to mwifiex_remove_card.

> makes sense for the kernel not to report that the card was removed,
> since it wasn't actually removed. Only the module was unloaded.
> 
> >> Under this kernel, I'm not sure if the power is or isn't being cut at
> >> this point. I don't think this is relevant though; regular
> >
> > "we quite regularly will power down the wireless card when it is not
> > being actively used..."
> >
> > I interpreted this statement as "the power to the card is being cut while inactive".
> > mwifiex_remove_card() is called seems agrees with it. Perhaps I'm missing something here.
> 
> Yes, we will want to make sure that the power is physically cut. I
> just haven't verified what the exact behaviour is under 3.8.

MMC core will report "mmc0: card 0001 removed" when the power is cut.

> Nevertheless, I think this detail is irrelevant, given that
> rmmod/insmod cycles work fine, but the problem only occurs when
> scanning is involved.
> 
> >> insmod/rmmod cycles work fine, the problem only appears when tearing
> >> down the interface while a scan is in progress.
> >
> > Could you add some debug logs in the tear-down path to show where exactly it gets stuck?
> 
> I mis-spoke there, sorry. The problem happens on the next modprobe
> *after* a teardown when a scan was in progress. The teardown itself
> seems to have completed without getting stuck.
> 
> If you have any suggestions for where to add debug messages, that
> would be appreciated. Otherwise I will look into sprinkling a few
> throughout the probe sequences to see if any communication succeeds
> before the first error is printed.

For now, let's use dynamic_debug to collect some logs.

CONFIG_DYNAMIC_DEBUG=y

# run these commands before running the test script:
echo "module mwifiex +p" > /sys/kernel/debug/dynamic_debug/control
echo "module mwifiex_sdio +p" > /sys/kernel/debug/dynamic_debug/control

Thanks,
Bing