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SubjectRe: [PATCH v2] tracing: Fix event probe removal from dynamic events
On Wed, 13 Oct 2021 23:42:06 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> > > Actually, the dynamic_events delete command is something like wildcard
> > > unless you specify the options.
> >
> > OK, so we need to update this a little bit more. But currently, it fails if
> > you do:
> >
> > # echo 'e:hrstate timer/hrtimer_cancel state=+0x38($hrtimer):u8' >> dynamic_events
> > # cat dynamic_events
> > eprobes/hrstate timer.hrtimer_cancel state=+0x38($hrtimer):u8
>
> BTW, Isn't there 'e:' prefix like below?
> e:eprobes/hrstate timer.hrtimer_cancel state=+0x38($hrtimer):u8

Yes, that works too, but you can leave off the GROUP/ when creating the
event, which it will default to "eprobes/".

>
> > # echo '-:eprobes/hrstate timer.hrtimer_cancel state=+0x38($hrtimer):u8' >> dynamic_events
> >
> > It will error out with "-EBUSY".
>
> That may be another reason. (Did you enable the eprobes/hrstate?)
> If the event doesn't match, it will return -ENOENT.

Hmm, now trying to reproduce it, I'm getting:

-bash: echo: write error: No such file or directory

Which would be -ENOENT. Before I was getting -EBUSY when attaching eprobes
to kprobes with your $$args patch. But that's not applied right now, so I
can't try to reproduce it at the moment. I probably hit something else at
the time anyway.

But still, it's broken, and I need to fix it. I'll make the updates to
allow the above. Perhaps I'll include a test that tests the above too.

-- Steve

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