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Re: signalling a condvar from inside vs. signalling a condvar von outside

From "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>
Newsgroups comp.lang.c++
Subject Re: signalling a condvar from inside vs. signalling a condvar von outside
Date 2025-04-15 12:07 -0700
Organization A noiseless patient Spider
Message-ID <vtmapb$bjcc$1@dont-email.me> (permalink)
References (2 earlier) <vtgloc$36urv$1@raubtier-asyl.eternal-september.org> <vth3gt$3j0qm$1@dont-email.me> <vth5ig$3kqh7$1@raubtier-asyl.eternal-september.org> <vthb0p$3p9fh$1@dont-email.me> <vtl9ii$3dqu3$1@raubtier-asyl.eternal-september.org>

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On 4/15/2025 2:41 AM, Bonita Montero wrote:
> Am 13.04.2025 um 23:40 schrieb Chris M. Thomasson:
> 
>> You code is hard to read. ...
> 
> The code is beautiful.

I can understand it, but, well, shit happens. I would not say it's 
beautiful... But, that is just me. Again, shit happens.


>> Signalling while locked or unlocked was an old debate. Think of 
>> signalling
>> while holding the lock. A thread gets woken and immediately sees that the
>> lock is held. Oh well. Wait morphing  can help with that. However, signal
>> outside when you can...
> 
> The number of context-switches determined via getrusage() is twice per
> loop iteration, i.e. on switch to the thread and one switch from the
> thread; so everything is optimal with glibc.

In real applications there is generally more going on in those critical 
sections vs your test... Well, I have seen some horror shows in my life.

Again, think of a scenario where the lock is held. The thread signals... 
Another thread wakes up and has to instantly block on a wait morphing 
queue in the kernel. This is not "ideal". A signal outside of the mutex 
can be beneficial. Signalling outside can give a signaled thread a 
possible fast-path into the critical section, completely eliminating the 
need for kernel interaction. Now, an adaptive mutex can try to help with 
this via limited spinning... However, try to signal outside when you can.

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signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-12 17:23 +0200
  Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-12 12:33 -0700
    Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-13 17:38 +0200
      Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-13 12:32 -0700
        Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-13 22:08 +0200
          Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-13 14:40 -0700
            Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-15 11:41 +0200
              Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-15 12:07 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-16 06:12 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-16 15:59 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-17 05:58 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-16 22:26 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-17 13:20 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-17 10:51 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-18 07:56 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-18 12:42 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-18 22:05 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 02:25 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-19 11:29 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 03:10 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 03:12 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-19 14:09 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 07:34 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 07:35 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-19 17:24 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 19:33 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside scott@slp53.sl.home (Scott Lurndal) - 2025-04-19 14:55 +0000
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-19 17:25 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside scott@slp53.sl.home (Scott Lurndal) - 2025-04-19 22:59 +0000
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-20 06:19 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-20 06:29 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 22:43 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-20 07:45 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-19 22:49 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-20 09:07 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-20 14:17 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-20 14:18 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-21 06:55 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-21 17:28 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-22 07:16 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-22 14:36 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-23 07:13 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-23 12:08 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-24 06:30 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-24 13:00 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-24 19:02 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-24 12:59 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-24 23:11 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-23 07:46 +0200
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-24 13:05 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-24 13:15 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2025-04-24 13:17 -0700
                Re: signalling a condvar from inside vs. signalling a condvar von outside Bonita Montero <Bonita.Montero@gmail.com> - 2025-04-24 23:10 +0200

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