Messages in this thread | | | Date | Mon, 6 Aug 2018 14:48:40 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/2] perf/hw_breakpoint: Modify breakpoint even if the new attr has disabled set |
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On 08/06, Jiri Olsa wrote: > > We need to change the breakpoint even if the attr with > new fields has disabled set to true.
Agreed... The patch looks fine to me, but I have a question
> int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr) > { > + int err; > + > /* > * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it > * will not be possible to raise IPIs that invoke __perf_event_disable. > @@ -520,11 +522,11 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att > else > perf_event_disable(bp); > > - if (!attr->disabled) { > - int err = modify_user_hw_breakpoint_check(bp, attr, false); > + err = modify_user_hw_breakpoint_check(bp, attr, false); > + if (err) > + return err; > > - if (err) > - return err; > + if (!attr->disabled) { > perf_event_enable(bp); > bp->attr.disabled = 0;
Afaics you do not need to clear attr.disabled, modify_user_hw_breakpoint_check() updates it if err = 0. So I think
if (!bp->attr.disabled) perf_event_enable(bp);
will look a bit better.
But, with or without this fix, shouldn't we set .disabled = 1 if modify_() fails? IIUC this doesn't matter, bp->attr.disabled is not really used anyway, but looks a bit confusing.
Oleg.
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