Messages in this thread | | | Date | Mon, 21 Aug 2017 17:01:38 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] perf/core: fix group {cpu,task} validation |
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On Mon, Aug 21, 2017 at 05:53:26PM +0200, Peter Zijlstra wrote: > On Thu, Jun 22, 2017 at 03:41:38PM +0100, Mark Rutland wrote: > > Regardless of which events form a group, it does not make sense for the > > events to target different tasks and/or CPUs, as this leaves the group > > inconsistent and impossible to schedule. The core perf code assumes that > > these are consistent across (successfully intialised) groups. > > > > Core perf code only verifies this when moving SW events into a HW > > context. Thus, we can violate this requirement for pure SW groups and > > pure HW groups, unless the relevant PMU driver happens to perform this > > verification itself. These mismatched groups subsequently wreak havoc > > elsewhere. > > > > For example, we handle watchpoints as SW events, and reserve watchpoint > > HW on a per-cpu basis at pmu::event_init() time to ensure that any event > > that is initialised is guaranteed to have a slot at pmu::add() time. > > However, the core code only checks the group leader's cpu filter (via > > event_filter_match()), and can thus install follower events onto CPUs > > violating thier (mismatched) CPU filters, potentially installing them > > into a CPU without sufficient reserved slots. > > > Fix this by validating this requirement regardless of whether we're > > moving events. > > Yes, and this also appears to cure your other problem: > > https://lkml.kernel.org/r/20170810173551.GD12812@leverpostej
Ah; sorry for the duplicate report! I should have realised.
I guess this will get queued soon?
Thanks, Mark.
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