Messages in this thread | | | Date | Fri, 7 Jul 2017 08:50:40 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 21/21] x86/intel_rdt/mbm: Handle counter overflow |
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On Thu, 6 Jul 2017, Shivappa Vikas wrote: > On Sun, 2 Jul 2017, Thomas Gleixner wrote: > > On Mon, 26 Jun 2017, Vikas Shivappa wrote: > > > +static void mbm_update(struct rdt_domain *d, int rmid) > > > +{ > > > + struct rmid_read rr; > > > + > > > + rr.first = false; > > > + rr.d = d; > > > + > > > + if (is_mbm_total_enabled()) { > > > + rr.evtid = QOS_L3_MBM_TOTAL_EVENT_ID; > > > + __mon_event_count(rmid, &rr); > > > > This is broken as it is not protected against a concurrent read from user > > space which comes in via a smp function call. > > The read from user also has the rdtgroup_mutex.
Which is again, completely non obvious and undocumented in the code.
Aside of that, are you really serious about serializing the world and everything on a single global mutex?
Thanks,
tglx
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