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Date:   Mon, 11 Apr 2022 07:36:26 -0700
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From:   Dave Hansen <dave.hansen@intel.com>
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID
 allocation and free it on mm exit
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On 4/11/22 07:20, zhangfei.gao@foxmail.com 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?