Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit

[Dave Hansen]

On 4/11/22 07:20, zhangfei.gao@xxxxxxxxxxx wrote:
>> Is there nothing before this call trace?  Usually there will be at least
>> some warning text.
> I added dump_stack() in ioasid_free.

Hold on a sec, though...

What's the *problem* here?  Did something break or are you just saying
that something looks weird to _you_?

For instance, if we have:

	nginx: ioasid_alloc()==1
	       fork(); // spawn the daemon
	       exit();
	       ioasid_free(1);

and then a moment later:

	lynx:  ioasid_alloc()==1
	       fork();
	       exit();
	       ioasid_free(1);

There's no problem.  The original nginx process with ioasid==1 exited.
The fact that *some* process called nginx is still running doesn't mean
that it still has a reference to asid==1.

Are you sure the nginx process that allocated the ASID is the same
process you see in ps?