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Subject: Re: [PATCH] mailbox: pcc: Synchronize channel IRQ before unmapping
 shared memory
To: Sudeep Holla <sudeep.holla@kernel.org>
Cc: Jassi Brar <jassisinghbrar@gmail.com>, linux-acpi@vger.kernel.org,
 linux-kernel@vger.kernel.org, stable@vger.kernel.org
References: <20260828161033.3783599-1-christian.loehle@arm.com>
 <20260903-impetuous-exceptional-python-db8aba@sudeepholla>
 <20260903-subtle-cornflower-guppy-b64a03@sudeepholla>
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From: Christian Loehle <christian.loehle@arm.com>
In-Reply-To: <20260903-subtle-cornflower-guppy-b64a03@sudeepholla>
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On 9/3/26 10:10, Sudeep Holla wrote:
> On Thu, Sep 03, 2026 at 10:03:38AM +0100, Sudeep Holla wrote:
>> On Fri, Aug 28, 2026 at 05:10:33PM +0100, Christian Loehle wrote:
>>> pcc_mbox_free_channel() unmaps the PCC shared-memory region before
>>> mbox_free_channel() invokes the controller shutdown callback. For
>>> interrupt-capable extended subspaces, an in-flight handler may
>>> consequently access the mapping after it has been invalidated.
>>>
>>> Release the mailbox channel first so its IRQ is disabled and synchronized
>>> before unmapping the shared-memory region. Serialize PCC channel
>>> acquisition and release across this sequence: once mbox_free_channel()
>>> makes the channel available, another client must not replace the
>>> shared-memory mapping until the old one has been unmapped.
>>>
>>
>> Breno Leitao has already posted the fix for the unmapping before freeing
>> the channel. You just need the mutex guards.
>>
> 
> Failed to add the reference to it [1] earlier.
> 

Thanks, I didn't see that.
I guess I'll wait until Breno's patch hits linux-next
or linus' tree and rebase?