netdev - Re: [PATCH net-next 08/14] bnxt_en: Add BNXT_STATE_IN_FW_RESET state and pf->registered

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Message-Id: <20190825.225957.2229146461648644754.davem@davemloft.net>
Date:   Sun, 25 Aug 2019 22:59:57 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     michael.chan@...adcom.com
Cc:     netdev@...r.kernel.org, vasundhara-v.volam@...adcom.com,
        jiri@...lanox.com, ray.jui@...adcom.com
Subject: Re: [PATCH net-next 08/14] bnxt_en: Add BNXT_STATE_IN_FW_RESET
 state and pf->registered_vfs.

From: Michael Chan <michael.chan@...adcom.com>
Date: Sun, 25 Aug 2019 23:54:59 -0400

> @@ -9234,6 +9243,13 @@ int bnxt_close_nic(struct bnxt *bp, bool irq_re_init, bool link_re_init)
>  {
>  	int rc = 0;
>  
> +	while (test_bit(BNXT_STATE_IN_FW_RESET, &bp->state)) {
> +		netdev_info(bp->dev, "FW reset in progress, delaying close");
> +		rtnl_unlock();
> +		msleep(250);
> +		rtnl_lock();
> +	}

Dropping the RTNL here is extremely dangerous.

Operations other than actual device close can get into the
bnxt_close_nic() code paths (changing features, ethtool ops, etc.)

So we can thus re-enter this function once you drop the RTNL mutex.

Furthermore, and I understand what pains you go into in patch #9 to
avoid this, but it's an endless loop.  If there are bugs there, we
will get stuck in this close path forever.