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Subject: Re: [RFC v7 24/25] powerpc: Deliver SEGV signal on pkey violation
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Ram Pai <linuxram@us.ibm.com>, Michael Ellerman <mpe@ellerman.id.au>
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On Fri, 2017-08-18 at 10:04 -0700, Ram Pai wrote:
> Assume two threads of a task.
> 
> T1:  mprotect_key(foo, PAGE_SIZE, pkey=4);
> T1:  set AMR to disable access for pkey 4;
> T1:  key fault
>     T2: set AMR to enable access to pkey 4;
> T1:  fault handler called.
>         This fault handler will see the new AMR and not the
>         one at the time of the fault.

You aren't context switching AMR with the threads ? Ugh... something is
very wrong then.

Ben.