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Subject: Re: [PATCH] brcmfmac: change the order of things in brcmf_detach()
To:     Piotr Figiel <p.figiel@camlintechnologies.com>
Cc:     =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <rafal@milecki.pl>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
References: <1556532561-24428-1-git-send-email-arend.vanspriel@broadcom.com>
 <20190430081142.GA27822@phoenix>
From:   Arend Van Spriel <arend.vanspriel@broadcom.com>
Message-ID: <74b9f312-8c1a-daa8-6137-c664d37f06d1@broadcom.com>
Date:   Tue, 30 Apr 2019 12:10:26 +0200
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On 4/30/2019 10:11 AM, Piotr Figiel wrote:
> Hi Arend,
> 
> On Mon, Apr 29, 2019 at 12:09:21PM +0200, Arend van Spriel wrote:
>> When brcmf_detach() from the bus layer upon rmmod we can no longer
>> communicate. Hence we will set the bus state to DOWN and cleanup
>> the event and protocol layer. The network interfaces need to be
>> deleted before brcmf_cfg80211_detach() because the latter does the
>> wiphy_unregister() which issues a warning if there are still network
>> devices linked to the wiphy instance.
> 
> This seems to already happen - brcmf_cfg80211_detach() is called after the
> interfaces are removed.

Right. This was just to remind me why brcmf_cfg80211_detach() must be 
called after removing the interfaces.

>> This change solves a null pointer dereference issue which happened
>> upon issueing rmmod while there are packets queued in bus protocol
>> layer.
>>
>> Reported-by: Rafał Miłecki <rafal@milecki.pl>
>> Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
>> Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
>> Reviewed-by: Franky Lin <franky.lin@broadcom.com>
>> Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
>> ---
>> Hi Piotr,
>>
>> While working on an issue with msgbuf protocol (used for PCIe devices)
>> your change 5cdb0ef6144f ("brcmfmac: fix NULL pointer derefence during
>> USB disconnect") conflicted. I suspect my reordering stuff in
>> brcmf_detach() also fixes your issue so could you retest this patch,
>> which basically reverts your change and applies my reordering, and see
>> whether my suspicion can be confirmed.
> 
> Does the issue reported by Rafał you are trying to solve with this patch occur
> on current linux-next?

Looking at you patch I suspect it does, because 
brcmf_proto_msgbuf_detach() is invoked in 
brcmf_proto_detach_post_delif(). However, I could not reproduce it with 
or without the patch.

Rafał,

Do you know whether your reported issue, ie. calling brcmf_tx_finalize() 
after interfaces were removed, still exists in wireless-testing (or 
linux-next).

Regards,
Arend