On Wed, Oct 18, 2017 at 01:25:48PM +1100, Balbir Singh wrote: > On Fri, 18 Aug 2017 15:36:55 -0700 > Ram Pai <linux...@us.ibm.com> wrote: > > > On Sat, Aug 19, 2017 at 07:54:20AM +1000, Benjamin Herrenschmidt wrote: > > > 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. > > > > I do store and restore AMR accross context switch. So nevermind; the > > above problem cannot happen. > > > > I think the assumption is that pkey_alloc() will do the right thing > while allocating keys across threads
It does. A key allocated to a thread will never be allocated to another thread. RP
