linux-kernel - Re: [PATCH v3 46/57] perf: Simplify pmu_dev

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Message-ID: <29924c50-cf96-13bb-ef84-4813caa3aef3@redhat.com>
Date:   Mon, 12 Jun 2023 14:29:05 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>
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Subject: Re: [PATCH v3 46/57] perf: Simplify pmu_dev_alloc()

On 6/12/23 14:18, Greg KH wrote:
> Yeah, it's a pain, but you are trying to hand-roll code that is not a
> "normal" path for a struct device, sorry.
> 
> I don't know if you really can encode all of that crazy logic in the
> cleanup api, UNLESS you can "switch" the cleanup function at a point in
> time (i.e. after device_add() is successful).  Is that possible?

What _could_ make sense is that device_add() completely takes ownership 
of the given pointer, and takes care of calling put_device() on failure.

Then you can have

	struct device *dev_struct __free(put_device) =
		kzalloc(sizeof(struct device), GFP_KERNEL);

	struct device *dev __free(device_del) =
		device_add(no_free_ptr(dev_struct));

	/* dev_struct is NULL now */

	pmu->dev = no_free_ptr(dev);

Paolo