Re: [PATCH 1/2] remoteproc: core: Attach rproc asynchronously in rproc_add() path

[Jingyi Wang <jingyi.wang@oss.qualcomm.com>]

On 4/10/2026 10:28 PM, Stephan Gerhold wrote:
> +Cc Bartosz, Dmitry
> 
> On Thu, Apr 09, 2026 at 01:46:21AM -0700, Jingyi Wang wrote:
>> For rproc with state RPROC_DETACHED and auto_boot enabled, the attach
>> callback will be called in the rproc_add()->rproc_trigger_auto_boot()->
>> rproc_boot() path, the failure in this path will cause the rproc_add()
>> fail and the resource release, which will cause issue like rproc recovery
>> or falling back to firmware load fail. Add attach_work for rproc and call
>> it asynchronously in rproc_add() path like what rproc_start() do.
>>
>> Signed-off-by: Jingyi Wang <jingyi.wang@oss.qualcomm.com>
>> ---
>>   drivers/remoteproc/remoteproc_core.c | 20 ++++++++++++--------
>>   include/linux/remoteproc.h           |  1 +
>>   2 files changed, 13 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
>> index b087ed21858a..f02db1113fae 100644
>> --- a/drivers/remoteproc/remoteproc_core.c
>> +++ b/drivers/remoteproc/remoteproc_core.c
>> @@ -1673,18 +1673,21 @@ static void rproc_auto_boot_callback(const struct firmware *fw, void *context)
>>   	release_firmware(fw);
>>   }
>>   
>> +static void rproc_attach_work(struct work_struct *work)
>> +{
>> +	struct rproc *rproc = container_of(work, struct rproc, attach_work);
>> +
>> +	rproc_boot(rproc);
>> +}
>> +
>>   static int rproc_trigger_auto_boot(struct rproc *rproc)
>>   {
>>   	int ret;
>>   
>> -	/*
>> -	 * Since the remote processor is in a detached state, it has already
>> -	 * been booted by another entity.  As such there is no point in waiting
>> -	 * for a firmware image to be loaded, we can simply initiate the process
>> -	 * of attaching to it immediately.
>> -	 */
>> -	if (rproc->state == RPROC_DETACHED)
>> -		return rproc_boot(rproc);
>> +	if (rproc->state == RPROC_DETACHED) {
>> +		schedule_work(&rproc->attach_work);
>> +		return 0;
>> +	}
> 
> I think the change itself is reasonable to make "auto-attach" behavior
> consistent with "auto-boot". The commit message is a bit misleading
> though:
> 
>   - You're really doing two separate functional changes here:
> 
>     (1) Ignore the return value of rproc_boot() during auto-boot attach,
>         to keep the remoteproc registered and available in sysfs even if
>         attaching fails.
>     (2) Run the rproc_boot() in the background using schedule_work().
>         [To improve boot performance? To work around some locking issues?]
> 
>   - The actual issue you are seeing sounds like a use-after-free in the
>     remoteproc core error cleanup path. I think this one is still
>     present, we should really have a call to
>     cancel_work_sync(&rproc->crash_handler) as Dmitry wrote in the
>     previous discussion [1].
> 
> Thanks,
> Stephan
> 
> [1]: https://lore.kernel.org/all/ce24a2sgg4b6wymoxwgl2ve6np2nxn2wuxfqxfpmvqqrpvgouf@xihd6ziqwu4m/

Hi Stephan,

Exactly as you say, what this change do is allowing rproc_attach return false.
It should be okay to keep this change and describe it more clear in commit msg
in next version?

And the use-after-free issue is what we want to resolve in the patch2
in this series, I think cancel_work_sync() is a reasonable change
but it cannot resolve this issue as the worker could be executing when
we call this(and this is what it behaves when I did local test) and
the use-after-free issue still exists. Shall we send a separate patch
for this cancel_work_sync?

Thanks,
Jingyi