linux-kernel - Re: [PATCH] tracepoint: Do not fail unregistering a probe due to memory allocation

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Date:   Tue, 17 Nov 2020 16:22:23 -0500 (EST)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     rostedt <rostedt@...dmis.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Matt Mullins <mmullins@...x.us>,
        Ingo Molnar <mingo@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] tracepoint: Do not fail unregistering a probe due to
 memory allocation

----- On Nov 17, 2020, at 3:58 PM, rostedt rostedt@...dmis.org wrote:

> On Tue, 17 Nov 2020 15:34:51 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
[...]

> If it comes down to not trusting calling a stub, I'll still keep the stub
> logic in, and just add the following:

If we don't call the stub, then there is no point in having the stub at
all, and we should just compare to a constant value, e.g. 0x1UL. As far
as I can recall, comparing with a small immediate constant is more efficient
than comparing with a loaded value on many architectures.

Thanks,

Mathieu
 
-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com