Re: [RFC PATCH v3 2/3] tracing: Introduce tracepoint_is_syscall()

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

On 2024-10-27 21:23, Andrii Nakryiko wrote:
> On Sun, Oct 27, 2024 at 7:19 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:

[...]

>>>>   include/linux/tracepoint-defs.h |  2 ++
>>>>   include/linux/tracepoint.h      | 24 ++++++++++++++++++++++++
>>>>   include/trace/define_trace.h    |  2 +-
>>>>   3 files changed, 27 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
>>>> index 967c08d9da84..53119e074c87 100644
>>>> --- a/include/linux/tracepoint-defs.h
>>>> +++ b/include/linux/tracepoint-defs.h
>>>> @@ -32,6 +32,8 @@ struct tracepoint_func {
>>>>   struct tracepoint_ext {
>>>>      int (*regfunc)(void);
>>>>      void (*unregfunc)(void);
>>>> +   /* Flags. */
>>>> +   unsigned int syscall:1;
>>>
>>> I wonder if we should call it "sleepable" instead? For this patch set
>>> do we really care if it's a system call or not? It's really if the
>>> tracepoint is sleepable or not that's the issue. System calls are just
>>> one user of it, there may be more in the future, and the changes to BPF
>>> will still be needed.
>>
>> I agree with this. Even if currently we restrict only syscall events
>> can be sleep, "tracepoint_is_syscall()" requires to add comment to
>> explain why on all call sites e.g.
>>
> 
> +1 to naming this "sleepable" (or at least "faultable"). BPF world
> uses "sleepable BPF" terminology for BPF programs and attachment hooks
> that can take page fault (and wait/sleep waiting for those to be
> handled), so this would be consistent with that. Also, from BPF
> standpoint this will be advertised as attaching to sleepable
> tracepoints regardless, so "syscall" terminology is too specific and
> misleading, because while current set of tracepoints are
> syscall-specific, the important part is taking page fault, no tracing
> syscalls.

+1 for "faultable".

Thanks,

Mathieu

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