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From: "Joël Krähemann" <jkraehemann@gmail.com>
To: Sebastian Huber <sebastian.huber@embedded-brains.de>
Cc: libc-help@sourceware.org
Subject: Re: pthread_mutex_timedlock() vs. clock_settime()
Date: Mon, 1 Aug 2022 13:51:14 +0200	[thread overview]
Message-ID: <CA+Owze4RD+-07yB-y6yDZTekmL+_G=RPuXrL2iJNdf1Vg2Pjag@mail.gmail.com> (raw)
In-Reply-To: <CA+Owze4ArpcSENrM133BCm6OybUr_AhRQkWagHpFxMfUzikx3g@mail.gmail.com>

Hi Sebastian,

You should inform yourself better about the topic. Maybe read a manual
about conditional locks. Since you are doing it wrong.

All conditional locks take 2 condition variables, in order to prevent
race-condition.

See for example here:

https://git.savannah.nongnu.org/cgit/gsequencer.git/tree/ags/thread/ags_thread.c?id=393da4d9fdc6c50ef3ab8eab27b562c85bd57664#n2002

Or check this for condition:

~~~~

volatile int is_wait;
volatile int is_done;

static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER:
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

pthread_mutex_lock(&mutex);

if(g_atomic_int_get(&is_wait) &&
  !g_atomic_int_get(&is_done)){
  g_atomic_int_set(&is_wait, TRUE);

  while(g_atomic_int_get(&is_wait) &&
    !g_atomic_int_get(&is_done)){
    pthread_cond_wait(&cond);
  }
}

pthread_mutex_lock(&mutex);


~~~~

Then later signal:

~~~~

g_mutex_lock(&mutex);

g_atomic_int_set(&is_done, TRUE);

if(g_atomic_int_get(&is_wait)){
    pthread_cond_signal(&cond);
}

g_mutex_unlock(&mutex);

~~~~

regards,
Joël

On Mon, Aug 1, 2022 at 11:51 AM Joël Krähemann <jkraehemann@gmail.com> wrote:
>
> Hi,
>
> Sorry, you are right. Might be your conditional lock is buggy. I think
> of a race-condition ending in a dead-lock, because you don't do any
> initial sync.
>
> ^^ this is really probable, but let me check later.
>
> regards,
> Joël
>
>
> On Mon, Aug 1, 2022 at 10:36 AM Sebastian Huber
> <sebastian.huber@embedded-brains.de> wrote:
> >
> > On 01/08/2022 10:28, Joël Krähemann wrote:
> > > pthread_mutex_t mtx of struct test_context.
> > >
> > > You lock it in line 503 first, then you call test_timeout_finite(),
> > > which calls event_post() in run() second lock.
> >
> > the event_post() and event_get() use their own data structures with
> > dedicated mutexes and condition variables:
> >
> > typedef struct {
> >    int value;
> >    pthread_mutex_t mtx;
> >    pthread_cond_t cnd;
> > } event;
> >
> > --
> > embedded brains GmbH
> > Herr Sebastian HUBER
> > Dornierstr. 4
> > 82178 Puchheim
> > Germany
> > email: sebastian.huber@embedded-brains.de
> > phone: +49-89-18 94 741 - 16
> > fax:   +49-89-18 94 741 - 08
> >
> > Registergericht: Amtsgericht München
> > Registernummer: HRB 157899
> > Vertretungsberechtigte Geschäftsführer: Peter Rasmussen, Thomas Dörfler
> > Unsere Datenschutzerklärung finden Sie hier:
> > https://embedded-brains.de/datenschutzerklaerung/

  reply	other threads:[~2022-08-01 11:53 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-02  8:43 Sebastian Huber
2022-08-01  7:10 ` Joël Krähemann
2022-08-01  7:41   ` Joël Krähemann
2022-08-03 23:44   ` Sebastian Huber
2022-08-01  8:28     ` Joël Krähemann
2022-08-01  8:36       ` Sebastian Huber
2022-08-01  9:51         ` Joël Krähemann
2022-08-01 11:51           ` Joël Krähemann [this message]
2022-08-01 11:59             ` Joël Krähemann
2022-08-01 14:44               ` Joël Krähemann
2022-08-01 16:31             ` Sebastian Huber
2022-08-01 20:11               ` Joël Krähemann
2022-08-01 22:05                 ` Joël Krähemann

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