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Subject[PATCH 3/2] perf/hw_breakpoint: Remove superfluous bp->attr.disabled = 0 new attr has disabled set
On Mon, Aug 06, 2018 at 03:23:53PM +0200, Jiri Olsa wrote:
> On Mon, Aug 06, 2018 at 02:48:40PM +0200, Oleg Nesterov wrote:
> > 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.
> >
>
> yea, I was looking on that, but as u said it makes no difference
> and I wanted to keep the patch as simple as possible ;-)
>
> I'll send something on top of this patch

like this ;-)

jirka


---
Once the breakpoint was succesfully modified, the attr->disabled
value is in bp->attr.disabled. So there's no reason to set it
again, removing that.

Link: http://lkml.kernel.org/n/tip-v5oaellzsmyszv3rfucuxkp0@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
kernel/events/hw_breakpoint.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index fb229d9c7f3c..3e560d7609fd 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -526,10 +526,9 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att
if (err)
return err;

- if (!attr->disabled) {
+ if (!attr->disabled)
perf_event_enable(bp);
- bp->attr.disabled = 0;
- }
+
return 0;
}
EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
--
2.17.1
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