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Date:   Tue, 17 Nov 2020 17:16:37 -0500
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     linux-kernel <linux-kernel@vger.kernel.org>,
        Matt Mullins <mmullins@mmlx.us>,
        Ingo Molnar <mingo@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Dmitry Vyukov <dvyukov@google.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] tracepoint: Do not fail unregistering a probe due to
 memory allocation
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On Tue, 17 Nov 2020 16:22:23 -0500 (EST)
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> 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.

Why 0x1UL, and not just set it to NULL.

		do {							\
			it_func = (it_func_ptr)->func;			\
			__data = (it_func_ptr)->data;			\
			if (likely(it_func))				\
				((void(*)(void *, proto))(it_func))(__data, args); \
		} while ((++it_func_ptr)->func);


-- Steve