netdev - Re: [PATCH v1 2/2] net: rfkill: Fix a logic error within rfkill_set_hw_state

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Date: Wed, 12 Jun 2024 12:11:26 +0200
From: Johannes Berg <johannes@...solutions.net>
To: quic_zijuhu <quic_zijuhu@...cinc.com>, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	emmanuel.grumbach@...el.com
Cc: linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v1 2/2] net: rfkill: Fix a logic error within
 rfkill_set_hw_state_reason()

On Wed, 2024-06-12 at 17:43 +0800, quic_zijuhu wrote:
> On 6/12/2024 4:18 PM, Johannes Berg wrote:
> > On Fri, 2024-06-07 at 22:40 +0800, Zijun Hu wrote:
> > > Kernel API rfkill_set_hw_state_reason() wrongly gets previous block state
> > > by using its parameter @reason as reason mask.
> > 
> > Using reason as a mask is perfectly valid.
> > 
> > And checking that the bit changed also seems valid.
> > 
> i don't think so as explained below.
> let us assume @rfkill->hard_block_reasons has value
> RFKILL_HARD_BLOCK_SIGNAL which means block state before
> __rfkill_set_sw_state(..., true, RFKILL_HARD_BLOCK_NOT_OWNER) is invoked.
> 
> @prev should mean previous block state, @prev will have false based on
> current logic, it is wrong since rfkill have block state before the call.
> 
> > We might want to not schedule the worker if it's not needed, but that's
> > a different issue, I don't see a real bug here?
> > 
> the worker will be unneccessarily scheduled for above example based on
> current logic even if the rfkill always stay in block state.
> > 

But yes, this is right. It's just not a bug.

johannes