linux-kernel - RE: [RFC 1/5] iwlwifi: fix drv cleanup on opmode registration failure

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Date:   Sun, 19 Feb 2017 09:16:01 +0000
From:   "Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
To:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        "Berg, Johannes" <johannes.berg@...el.com>,
        "Coelho, Luciano" <luciano.coelho@...el.com>,
        "tj@...nel.org" <tj@...nel.org>,
        "arjan@...ux.intel.com" <arjan@...ux.intel.com>,
        "ming.lei@...onical.com" <ming.lei@...onical.com>,
        "zajec5@...il.com" <zajec5@...il.com>
CC:     "jeyu@...hat.com" <jeyu@...hat.com>,
        "rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        linuxwifi <linuxwifi@...el.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC 1/5] iwlwifi: fix drv cleanup on opmode registration
 failure

Hi Luis,

> 
> The firmware async callback handles the device's opmode start call, but
> optionally also allows opmode registration to take care of its opmode start. If
> the firmware callback handles it its error path in case of opmode start failure
> has a few pieces of code missing from the opmode registration. The opmode
> registration hanlder has no cleanup at all. Sync both error paths.
> 
> This should in theory fix a detangled drv from the drv list should either of the
> opmode modules loaded and handled registration for the drv.
> 
> The path of having the opmode registration deal with the drv opmode start is
> actually the more common path. The other path, from the async callback is
> rathe rare (1/8 or so times for me) -- it happens when the the opmode
> driver's init routine completed prior to the driver's async callback opmode
> start call.

I'd claim it should never happen unless you have several devices on the system using the same
opmode, or unless you do:
modprobe iwlwifi  #which will load iwl{d,m}vm
rmmod iwl{d,m}vm #and do _not_ remove iwlwifi
modprobe iwlwifi



> 
> Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> ---

Luca is OOO,  but this looks fine to me.


>  drivers/net/wireless/intel/iwlwifi/iwl-drv.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-drv.c
> b/drivers/net/wireless/intel/iwlwifi/iwl-drv.c
> index be466a074c1d..e198d6f5fcea 100644
> --- a/drivers/net/wireless/intel/iwlwifi/iwl-drv.c
> +++ b/drivers/net/wireless/intel/iwlwifi/iwl-drv.c
> @@ -1611,8 +1611,13 @@ int iwl_opmode_register(const char *name, const
> struct iwl_op_mode_ops *ops)
>  			continue;
>  		op->ops = ops;
>  		/* TODO: need to handle exceptional case */
> -		list_for_each_entry(drv, &op->drv, list)
> +		list_for_each_entry(drv, &op->drv, list) {
>  			drv->op_mode = _iwl_op_mode_start(drv, op);
> +			if (!drv->op_mode) {
> +				complete(&drv-
> >request_firmware_complete);
> +				device_release_driver(drv->trans->dev);
> +			}
> +		}
> 
>  		mutex_unlock(&iwlwifi_opmode_table_mtx);
>  		return 0;
> --
> 2.11.0