| Date | Thu, 5 Jun 2014 17:01:25 +0300 | Subject | Re: [PATCH 5/9] perf/x86: implement cross-HT corruption bug workaround | From | Maria Dimakopoulou <> |
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Are you saying it is illegal to call kmalloc() from this context?
kmalloc is needed because we need to allocate a new constraint struct since the static constraint cannot be modified.
Worst case we can statically allocate a second constraint struct in the event struct.
On Thu, Jun 5, 2014 at 4:48 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Wed, Jun 04, 2014 at 11:34:14PM +0200, Stephane Eranian wrote: > >> +static struct event_constraint * >> +intel_get_excl_constraints(struct cpu_hw_events *cpuc, struct perf_event *event, >> + struct event_constraint *c) >> +{ > >> + if (!(c->flags & PERF_X86_EVENT_DYNAMIC)) { >> + >> + /* >> + * in case we fail, we assume no counter >> + * is supported to be on the safe side >> + */ >> + cx = kmalloc(sizeof(*cx), GFP_KERNEL); >> + if (!cx) >> + return &emptyconstraint; >> + > > Ok, so forgive me if I'm wrong, but the way we get here is through: > > x86_schedule_event() > ->start_scheduling() > spin_lock() > ->get_event_constraints() > intel_get_excl_constraints() > kmalloc(.gfp=GFP_KERNEL) > > How can that ever work?
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