[PATCH 1/4] ath10k: provide firmware crash info via debugfs.

Kalle Valo kvalo at qca.qualcomm.com
Sun Jun 8 01:28:51 PDT 2014

Ben Greear <greearb at candelatech.com> writes:

> On 06/07/2014 05:55 AM, Kalle Valo wrote:
>> Ben Greear <greearb at candelatech.com> writes:
>>>>> I'm a bit leery of adding spin-locks in the dump routine just for
>>>>> this, but I can add and use a new spin-lock if you prefer.
>>>> Why a new spinlock? I didn't review the locking requirements, but I
>>>> would first check ar->data_lock can be used.
>>> I think it has to be a spin-lock because the crash dump is gathered
>>> in the irq handler, so I can't use a mutex as far as I know...
>>> I'll work on adding such a lock today.
>> I asked why add a _new_ spinlock as ar->data_lock is already a spinlock.
> Surely we do not want to impede traffic flow just to dump debug info?

I don't see data_lock being used anywhere in hotpath, but of course I
might have missed something. Anyway, if for optimisation reasons we need
to introduce a new lock that should happen for a specific case in hot
path. Handling firmware debug log events is not in that category.

> And, it is easier to review a specific spinlock rather than use one big
> global-ish lock and have to review every use of that lock for issues.

Sure, it's easier for you to just add a new lock and then forget :) But
not for me who would have to maintain 20 different locks for years to
come. My view is that a new lock should be added on very exceptional
cases and with good justifications.

Kalle Valo

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