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From: Jan Kiszka <jan.kiszka@siemens.com>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: "Petr Červenka" <grugh@centrum.cz>, Xenomai <xenomai@xenomai.org>
Subject: Re: rt_task_unblock() POSIX alternative
Date: Tue, 14 Apr 2020 12:43:53 +0200	[thread overview]
Message-ID: <50cc036c-3afd-5afd-8c94-3bdfa9d7aa6c@siemens.com> (raw)
In-Reply-To: <CAFLxGvyoGbnQULdswrikMg-tBetnq-UA5fn_0jqQd1BLgH2U6A@mail.gmail.com>

On 14.04.20 12:41, Richard Weinberger wrote:
> On Tue, Apr 14, 2020 at 12:29 PM Jan Kiszka <jan.kiszka@siemens.com> wrote:
>>> This interrupts the Linux syscall, yes. Does this also work when the
>>> thread blocks on the Xenomai/Cobalt side?
>>>
>>
>> That ::read is a Xenomai syscall, being handled in the end by
>> timerfd_read in the core. So, yes.
> 
> True that, once again I got tricked by wrapping. :-)
> 
>> There were two "tricks" needed: avoid syscall restart (as you already
>> noticed) and using __STD (i.e. __real) pthread_kill in order to get a
>> normal signal out. Oh, and the flag var should better be volatile, but
>> that may still work when lucky.
> 
> While we are here, is there a guarantee that rt_task_unblock() can unblock
> a thread in every situation?
> I have a large Xenomai 2 application on my desk which seems to assumes that.

IIRC, it does so for the native/alchemy API.

> 
> As far as I understand it, unblocking tasks is best effort.
> /me has pthread_mutex_lock() in mind which must not return -EINTR as
> required by POSIX.
> 

Well, when mixing APIs, you can end up in such conflicting goals, indeed.

Jan

-- 
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux


  reply	other threads:[~2020-04-14 10:43 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-07 13:41 rt_task_unblock() POSIX alternative Petr Červenka
2020-04-07 14:59 ` Jan Kiszka
2020-04-07 15:18   ` Petr Červenka
2020-04-07 15:29     ` Jan Kiszka
2020-04-07 15:30     ` Richard Weinberger
2020-04-08  9:44       ` Petr Červenka
2020-04-08 10:06         ` Richard Weinberger
2020-04-08 21:36         ` Richard Weinberger
2020-04-09 15:00           ` Petr Červenka
2020-04-09 16:13             ` Richard Weinberger
2020-04-09 18:10               ` Petr Červenka
2020-04-09 18:48                 ` Richard Weinberger
2020-04-14  8:16                   ` Petr Červenka
2020-04-14  8:30                     ` Richard Weinberger
2020-04-14  9:10                       ` Petr Červenka
2020-04-14  9:46                         ` Richard Weinberger
2020-04-14 10:07                           ` Jan Kiszka
2020-04-14 10:23                             ` Richard Weinberger
2020-04-14 10:28                               ` Jan Kiszka
2020-04-14 10:41                                 ` Richard Weinberger
2020-04-14 10:43                                   ` Jan Kiszka [this message]
2020-04-14 10:56                                     ` Richard Weinberger
2020-04-14 11:01                                       ` Jan Kiszka
2020-04-14 11:05                                         ` Richard Weinberger
2020-04-14 11:30                                           ` Jan Kiszka
2020-04-14 10:39                             ` Petr Červenka

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