Re: PARI/GP 2.17.2 testsuite hangs nondeterministically (macOS)

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Sun, Oct 26, 2025 at 02:21:37PM -0700, Matthias Koeppe wrote:
> Unsurprisingly, builds using the clang compilers provided by
> conda-forge are also affected.
> https://github.com/passagemath/passagemath/actions/runs/18811959899/job/53674549752#step:10:2578

The following stand-alone program that does not use libpari also hangs when run
repeatly.

Try for example
for i in `seq 1 2000`; do echo $i; ./pthread1; done

Cheers,
Bill

/* Copyright (C) 2013  The PARI group.

This file is part of the PARI/GP package.

PARI/GP is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version. It is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY WHATSOEVER.

Check the License for details. You should have received a copy of it, along
with the package; see the file 'COPYING'. If not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

struct mt_state
{
  long workid;
};

struct pari_thread
{
  void * data;
};

struct pari_mt
{
  struct mt_state mt;
};

struct mt_queue
{
  long no;
  long input, output;
  long workid;
  long avma;
  pthread_cond_t cond;
  pthread_mutex_t mut;
  pthread_cond_t *pcond;
  pthread_mutex_t *pmut;
};


struct mt_pstate
{
  pthread_t *th;
  struct pari_thread *pth;
  struct mt_queue *mq;
  long n, nbint, last;
  long pending;
  pthread_cond_t pcond;
  pthread_mutex_t pmut;
};

static __thread long mt_thread_no = -1;
static struct mt_pstate *pari_mt;

#define LOCK(x) pthread_mutex_lock(x); do
#define UNLOCK(x) while(0); pthread_mutex_unlock(x)

void
mt_thread_init(void) { mt_thread_no = 0; }

void *
pari_thread_start(struct pari_thread *t)
{
  mt_thread_init();
  return t->data;
}

static void pari_mt_init(void)
{
  pari_mt = NULL;
}

static void
mt_queue_cleanup(void *arg)
{
  (void) arg;
}

static void
mt_queue_unlock(void *arg)
{ pthread_mutex_unlock((pthread_mutex_t*) arg); }

static void*
mt_queue_run(void *arg)
{
  void *args = pari_thread_start((struct pari_thread*) arg);
  struct mt_queue *mq = (struct mt_queue *) args;
  mt_thread_no = mq->no;
  pthread_cleanup_push(mt_queue_cleanup,NULL);
  LOCK(mq->pmut)
  {
    mq->avma = 1;
    pthread_cond_signal(mq->pcond);
  } UNLOCK(mq->pmut);
  for(;;)
  {
    long done;
    LOCK(&mq->mut)
    {
      pthread_cleanup_push(mt_queue_unlock, &mq->mut);
      while(!mq->input)
        pthread_cond_wait(&mq->cond, &mq->mut);
      pthread_cleanup_pop(0);
    } UNLOCK(&mq->mut);
    done = -1;
    pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS,NULL);
    for(long u=1; u<3000*mq->input;u++);
    pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED,NULL);
    LOCK(mq->pmut)
    {
      mq->input = 0;
      mq->output = done;
      pthread_cond_signal(mq->pcond);
    } UNLOCK(mq->pmut);
  }
  pthread_cleanup_pop(1);
  return NULL;
}

static long
mt_queue_check(struct mt_pstate *mt)
{
  long i;
  for(i=0; i<mt->n; i++)
  {
    struct mt_queue *mq = mt->mq+i;
    if (mq->output) return i;
  }
  return -1;
}

static long
mtpthread_queue_get(long *workid, long *pending)
{
  struct mt_pstate *mt = pari_mt;
  struct mt_queue *mq;
  long done = 0;
  long last;
  if (mt->nbint<mt->n)
  {
    mt->last = mt->nbint;
    *pending = mt->pending;
    return 0;
  }
  LOCK(&mt->pmut)
  {
    while ((last = mt_queue_check(mt)) < 0)
    {
      pthread_cond_wait(&mt->pcond, &mt->pmut);
    }
  } UNLOCK(&mt->pmut);
  mq = mt->mq+last;
  done = mq->output;
  mq->output = 0;
  if (workid) *workid = mq->workid;
  mt->last = last;
  mt->pending--;
  *pending = mt->pending;
  return done;
}

static void
mtpthread_queue_submit(long workid, long work)
{
  struct mt_pstate *mt = pari_mt;
  struct mt_queue *mq = mt->mq+mt->last;
  if (!work) { mt->nbint=mt->n; return; }
  if (mt->nbint<mt->n)
  {
    mt->nbint++;
    LOCK(mq->pmut)
    {
      while(!mq->avma)
        pthread_cond_wait(mq->pcond, mq->pmut);
    } UNLOCK(mq->pmut);
  }
  LOCK(&mq->mut)
  {
    mq->output = 0;
    mq->workid = workid;
    mq->input = work;
    pthread_cond_signal(&mq->cond);
  } UNLOCK(&mq->mut);
  mt->pending++;
}

void
mt_queue_reset(void)
{
  struct mt_pstate *mt = pari_mt;
  long i;
  for (i=0; i<mt->n; i++)
    pthread_cancel(mt->th[i]);
  for (i=0; i<mt->n; i++)
    pthread_join(mt->th[i],NULL);
  pari_mt = NULL;
  for (i=0;i<mt->n;i++)
  {
    struct mt_queue *mq = mt->mq+i;
    pthread_cond_destroy(&mq->cond);
    pthread_mutex_destroy(&mq->mut);
  }
  free(mt->mq);
  free(mt->pth);
  free(mt->th);
  free(mt);
}

void
mt_queue_start_lim(struct pari_mt *pt, long lim)
{
  struct mt_pstate *mt =
         (struct mt_pstate*) malloc(sizeof(struct mt_pstate));
  long i;
  mt->mq  = (struct mt_queue *) malloc(sizeof(*mt->mq)*lim);
  mt->th  = (pthread_t *) malloc(sizeof(*mt->th)*lim);
  mt->pth = (struct pari_thread *) malloc(sizeof(*mt->pth)*lim);
  mt->pending = 0;
  mt->n = lim;
  mt->nbint = 0;
  mt->last = 0;
  pthread_cond_init(&mt->pcond,NULL);
  pthread_mutex_init(&mt->pmut,NULL);
  for (i=0;i<lim;i++)
  {
    struct mt_queue *mq = mt->mq+i;
    mq->no     = i;
    mq->avma   = 0;
    mq->input  = 0;
    mq->output = 0;
    mq->pcond  = &mt->pcond;
    mq->pmut   = &mt->pmut;
    pthread_cond_init(&mq->cond,NULL);
    pthread_mutex_init(&mq->mut,NULL);
    mt->pth[i].data = (void*)mq;
  }
  for (i=0;i<lim;i++)
    pthread_create(&mt->th[i],NULL, &mt_queue_run, (void*)&mt->pth[i]);
  pari_mt = mt;
}

int
main(void)
{
  struct pari_mt pt;
  long i, j, k, workid = 0, pending = 0;
  pari_mt_init();
  for (k = 1; k<2; k++)
  {
    long nmax = 40;
    mt_queue_start_lim(&pt,8);
    for (i = 1; i <= nmax || pending;i++)
    {
      long s = i <= nmax ? i: 0;
      mtpthread_queue_submit(i, s);
      j = mtpthread_queue_get(&workid, &pending);
      if (j<0) break;
    }
    mt_queue_reset();
  }
  printf("Done!\n");
}