linux-kernel - Re: [PATCH net-next 1/5] net: ipa: use atomic exchange for suspend reference

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Date:   Tue, 08 Sep 2020 20:27:31 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     elder@...aro.org
Cc:     kuba@...nel.org, evgreen@...omium.org, subashab@...eaurora.org,
        cpratapa@...eaurora.org, bjorn.andersson@...aro.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/5] net: ipa: use atomic exchange for suspend
 reference

From: Alex Elder <elder@...aro.org>
Date: Tue,  8 Sep 2020 19:21:23 -0500

> We take a single IPA clock reference to keep the clock running
> until we get a system suspend operation.  When a system suspend
> request arrives, we drop that reference, and if that's the last
> reference (likely) we'll proceed with suspending endpoints and
> disabling the IPA core clock and interconnects.
> 
> In most places we simply set the reference count to 0 or 1
> atomically.  Instead--primarily to catch coding errors--use an
> atomic exchange to update the reference count value, and report
> an error in the event the previous value was unexpected.
> 
> In a few cases it's not hard to see that the error message should
> never be reported.  Report them anyway, but add some excitement
> to the message by ending it with an exclamation point.
> 
> Signed-off-by: Alex Elder <elder@...aro.org>

Please use refcount_t if you're wanting to validate things like
this.

Thank you.