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From: Philippe Gerum <rpm@xenomai.org>
Message-ID: <56211645.9090503@xenomai.org>
Date: Fri, 16 Oct 2015 17:22:45 +0200
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Subject: Re: [Xenomai] Xenomai 3: kill() to non-Xenomai PIDs
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To: Jan Kiszka <jan.kiszka@siemens.com>, Xenomai <xenomai@xenomai.org>

On 10/16/2015 04:56 PM, Jan Kiszka wrote:
> On 2015-10-16 16:49, Jan Kiszka wrote:
>> Hi,
>>
>> kill() is currently handled by libcobalt such that PIDs <= 0 are
>> forwarded to Linux and PIDs > 0 are considered to target only Xenomai
>> threads. But what if the user wants to address a regular Linux task from
>> within a Xenomai application? Shouldn't we retry kill via the Linux path
>> if Xenomai's syscall reports ESRCH?
>>
> 
> IOW:
> 
> diff --git a/lib/cobalt/signal.c b/lib/cobalt/signal.c
> index aac4059..7e03301 100644
> --- a/lib/cobalt/signal.c
> +++ b/lib/cobalt/signal.c
> @@ -99,6 +99,10 @@ COBALT_IMPL(int, kill, (pid_t pid, int sig))
>  
>  	ret = XENOMAI_SYSCALL2(sc_cobalt_kill, pid, sig);
>  	if (ret) {
> +		/* Retry with regular kill is no RT target was found. */
> +		if (ret == -ESRCH)
> +			return __STD(kill(pid, sig));
> +
>  		errno = -ret;
>  		return -1;
>  	}
> 
> Jan
> 

This may break code that sends signal 0 to detect whether a rt thread
exists (like copperplate does), which is the reason for the lack of
forwarding IIRC. (ret == -ESRCH && sig) would be required to forward
without breaking such assumption.

-- 
Philippe.