netdev - Re: [PATCH v4 net-next 11/19] ionic: Add Rx filter and rx

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Date:   Tue, 23 Jul 2019 17:19:54 -0700
From:   Shannon Nelson <snelson@...sando.io>
To:     David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH v4 net-next 11/19] ionic: Add Rx filter and rx_mode ndo
 support

On 7/23/19 4:06 PM, David Miller wrote:
> From: Shannon Nelson <snelson@...sando.io>
> Date: Tue, 23 Jul 2019 15:50:43 -0700
>
>> On 7/23/19 2:33 PM, David Miller wrote:
>>> Generally interface address changes are expected to be synchronous.
>> Yeah, this bothers me a bit as well, but the address change calls come
>> in under spin_lock_bh(), and I'm reluctant to make an AdminQ call
>> under the _bh that could block for a few seconds.
> So it's not about memory allocation but rather the fact that the device
> might take a while to complete?

Memory allocation may or may not be involved, but yes, mainly we're 
doing another spin_lock on a firmware command that waits for an ACK or 
ERROR answer, and in extreme cases could possibly timeout on a dead 
firmware.  I know that i40e and ice do much the same thing, and I 
believe mlx5 as well, for the same reasons.  I suspect others do as well.

> Can you start the operation synchronously yet complete it async?

This could be possible, but would likely require a bunch more messy 
logic to track async AdminQ requests, that otherwise is unnecessary.

sln