Re: [PATCH 16/17] uprobes: Allocate ->utask before handler_chain()for tracing handlers

[Oleg Nesterov]

On 12/11, Masami Hiramatsu wrote:
>
> (2013/12/11 0:57), Oleg Nesterov wrote:
> > On 12/10, Masami Hiramatsu wrote:
> >>
> >> and isn't it better to increment
> >> miss-hit counter of the uprobe?
> >
> > What do you mean? This is not miss-hit and ->utask == NULL is quite normal.
>
> But it could skip the handler_chain silently. It could confuse users
> why their probe doesn't hit as expected.

No, we will restart the same (probed) instruction, handle_swbp()
will be called again, get_utask() will be called again.

Not to mention that (in practice) if GFP_KERNEL fails the task is
already killed.

> > For example, on ppc it can be always NULL because ppc likely emulates the
> > probed insn.
>
> Hmm, in that case, should uprobes handlers never be called on ppc with
> this change?

Why? With this change ppc will have ->utask != NULL even if it doesn't
need it at all.

Oleg.

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