From: Mathieu Desnoyers <mathieu.desnoyers@efficios•com>
To: rostedt <rostedt@goodmis•org>
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
Date: Tue, 17 Nov 2020 18:08:19 -0500 (EST) [thread overview]
Message-ID: <1227896553.48834.1605654499161.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20201117171637.6aeeadd7@gandalf.local.home>
----- On Nov 17, 2020, at 5:16 PM, rostedt rostedt@goodmis•org wrote:
> 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);
Because of this end-of-loop condition ^
which is also testing for a NULL func. So if we reach a stub, we end up stopping
iteration and not firing the following tracepoint probes.
Thanks,
Mathieu
>
>
> -- Steve
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2020-11-17 23:09 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 22:51 [PATCH] tracepoint: Do not fail unregistering a probe due to memory allocation Steven Rostedt
2020-11-16 23:16 ` Steven Rostedt
2020-11-17 19:15 ` Mathieu Desnoyers
2020-11-17 19:21 ` Steven Rostedt
2020-11-17 19:47 ` Mathieu Desnoyers
2020-11-17 20:34 ` Steven Rostedt
2020-11-17 20:58 ` Steven Rostedt
2020-11-17 21:22 ` Mathieu Desnoyers
2020-11-17 22:16 ` Steven Rostedt
2020-11-17 23:08 ` Mathieu Desnoyers [this message]
2020-11-18 1:11 ` Steven Rostedt
2020-11-17 21:08 ` Mathieu Desnoyers
2020-11-18 13:21 ` violating function pointer signature Peter Zijlstra
2020-11-18 13:59 ` Florian Weimer
2020-11-18 14:12 ` Peter Zijlstra
2020-11-18 14:18 ` Florian Weimer
2020-11-18 14:34 ` [PATCH v3] tracepoint: Do not fail unregistering a probe due to memory allocation Steven Rostedt
2020-11-24 5:59 ` Matt Mullins
2020-11-18 14:22 ` violating function pointer signature Steven Rostedt
2020-11-18 19:46 ` Alexei Starovoitov
2020-11-18 20:02 ` Steven Rostedt
2020-11-18 14:02 ` Steven Rostedt
2020-11-18 16:01 ` Mathieu Desnoyers
2020-11-18 16:19 ` David Laight
2020-11-18 16:50 ` Nick Desaulniers
2020-11-18 17:17 ` Steven Rostedt
2020-11-18 18:12 ` Segher Boessenkool
2020-11-18 18:31 ` Florian Weimer
2020-11-18 18:55 ` Segher Boessenkool
2020-11-18 18:58 ` Steven Rostedt
2020-11-18 18:59 ` Steven Rostedt
2020-11-18 19:11 ` Segher Boessenkool
2020-11-18 19:33 ` Steven Rostedt
2020-11-18 19:48 ` Segher Boessenkool
2020-11-18 20:44 ` Steven Rostedt
2020-11-19 8:21 ` Peter Zijlstra
2020-11-19 8:36 ` Peter Zijlstra
2020-11-19 14:37 ` Segher Boessenkool
2020-11-19 14:59 ` Steven Rostedt
2020-11-19 16:35 ` Segher Boessenkool
2020-11-19 17:42 ` David Laight
2020-11-19 19:27 ` Segher Boessenkool
2020-11-19 17:04 ` Alexei Starovoitov
2020-11-19 17:30 ` Steven Rostedt
2020-11-20 1:31 ` Nick Desaulniers
2020-11-17 21:33 ` [PATCH] tracepoint: Do not fail unregistering a probe due to memory allocation Kees Cook
2020-11-17 22:19 ` Steven Rostedt
2020-11-17 23:12 ` Mathieu Desnoyers
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