From: Cambda Zhu <cambda@linux.alibaba.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
Dust Li <dust.li@linux.alibaba.com>,
Tony Lu <tonylu@linux.alibaba.com>
Subject: Re: Syscall kill() can send signal to thread ID
Date: Fri, 23 Sep 2022 16:40:15 +0800 [thread overview]
Message-ID: <613994F7-054D-4992-A159-96D34B17BC7F@linux.alibaba.com> (raw)
In-Reply-To: <87illeedc5.fsf@oldenburg.str.redhat.com>
> On Sep 23, 2022, at 15:53, Florian Weimer <fweimer@redhat.com> wrote:
>
>> I don't quite understand what you mean, sorry. But if kill() returns
>> -ESRCH for tid which is not equal to tgid, kill() can only send signal
>> to thread group via main thread id, that is what BSD did and manual
>> said. It seems not odd?
>
> It's still odd because there's one TID per process that's valid for
> kill by accident. That's all.
>
> Thanks,
> Florian
As far as I know, there is no rule forbidding 'process ID'(TGID on Linux)
equals to main thread ID, is it right? If one wants to send signal to a
specific thread, tgkill() can do that. As far as I understand, the difference
between kill() and tgkill() is whether the signal is set on shared_pending,
whatever the ID is a process ID or a thread ID. For Linux, the main thread ID
just equals to the process ID. So the meaning of kill(main_tid, sig) is sending
signal to a process, of which the PID equals to the first argument. It's not odd,
I think.
Thanks,
Cambda
next prev parent reply other threads:[~2022-09-23 8:40 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-22 9:11 Syscall kill() can send signal to thread ID cambda
2022-09-22 15:09 ` Eric W. Biederman
2022-09-23 5:31 ` Florian Weimer
2022-09-23 6:25 ` cambda
2022-09-23 7:53 ` Florian Weimer
2022-09-23 8:40 ` Cambda Zhu [this message]
2022-09-23 21:15 ` Eric W. Biederman
2022-09-22 15:33 ` Eric W. Biederman
2022-09-23 3:56 ` cambda
2022-09-23 11:24 ` David Laight
2022-09-23 21:21 ` Eric W. Biederman
2022-09-24 3:16 ` Cambda Zhu
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