From mboxrd@z Thu Jan 1 00:00:00 1970 References: <56210E7E.1050606@siemens.com> <5621102C.4030902@siemens.com> <56211645.9090503@xenomai.org> <56211787.8090107@siemens.com> <5621184E.8070704@xenomai.org> From: Jan Kiszka Message-ID: <56211E6A.2080300@siemens.com> Date: Fri, 16 Oct 2015 17:57:30 +0200 MIME-Version: 1.0 In-Reply-To: <5621184E.8070704@xenomai.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Xenomai 3: kill() to non-Xenomai PIDs List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum , Xenomai On 2015-10-16 17:31, Philippe Gerum wrote: > On 10/16/2015 05:28 PM, Jan Kiszka wrote: >> On 2015-10-16 17:22, Philippe Gerum wrote: >>> 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. >> >> That still breaks POSIX (what if the user wants to test for a non-rt >> thread, like this is possible under regular Linux?). Can't copperplate >> be changed to bypass the wrapper? >> > > Probably, yes. > Looking at cluster_probe, I wonder if there is actually a problem. Doesn't that code also run over mercury? Then kill(pid, 0) also targets the whole system, not just a set of Xenomai applications. Or do we need to ensure that the caller is not migrated to Linux needlessly under cobalt? IOW: can that probing happen under RT constraints? The same applies for me to the other users of the kill-based probing pattern (copperplate/heapobj-pshared.c and copperplate/regd/fs-common.c). Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux