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

Dave Hansen
2022-04-11T14:36:27Z

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?