glibc/nptl/pthread_setattr_default_np.c

/* Set the default attributes to be used by pthread_create in the process.
   Copyright (C) 2013-2020 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <stdlib.h>
#include <pthreadP.h>
#include <string.h>


int
pthread_setattr_default_np (const pthread_attr_t *in)
{
  const struct pthread_attr *real_in;
  struct pthread_attr attrs;
  int ret;

  real_in = (struct pthread_attr *) in;

  /* Catch invalid values.  */
  int policy = real_in->schedpolicy;
  ret = check_sched_policy_attr (policy);
  if (ret)
    return ret;

  const struct sched_param *param = &real_in->schedparam;
  if (param->sched_priority > 0)
    {
      ret = check_sched_priority_attr (param->sched_priority, policy);
      if (ret)
	return ret;
    }

  /* stacksize == 0 is fine.  It means that we don't change the current
     value.  */
  if (real_in->stacksize != 0)
    {
      ret = check_stacksize_attr (real_in->stacksize);
      if (ret)
	return ret;
    }

  /* Having a default stack address is wrong.  */
  if (real_in->flags & ATTR_FLAG_STACKADDR)
    return EINVAL;

  attrs = *real_in;

  /* Now take the lock because we start writing into
     __default_pthread_attr.  */
  lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);

  /* Free the cpuset if the input is 0.  Otherwise copy in the cpuset
     contents.  */
  size_t cpusetsize = attrs.cpusetsize;
  if (cpusetsize == 0)
    {
      free (__default_pthread_attr.cpuset);
      __default_pthread_attr.cpuset = NULL;
    }
  else if (cpusetsize == __default_pthread_attr.cpusetsize)
    {
      attrs.cpuset = __default_pthread_attr.cpuset;
      memcpy (attrs.cpuset, real_in->cpuset, cpusetsize);
    }
  else
    {
      /* This may look wrong at first sight, but it isn't.  We're freeing
	 __default_pthread_attr.cpuset and allocating to attrs.cpuset because
	 we'll copy over all of attr to __default_pthread_attr later.  */
      cpu_set_t *newp = realloc (__default_pthread_attr.cpuset,
				 cpusetsize);

      if (newp == NULL)
	{
	  ret = ENOMEM;
	  goto out;
	}

      attrs.cpuset = newp;
      memcpy (attrs.cpuset, real_in->cpuset, cpusetsize);
    }

  /* We don't want to accidentally set the default stacksize to zero.  */
  if (attrs.stacksize == 0)
    attrs.stacksize = __default_pthread_attr.stacksize;
  __default_pthread_attr = attrs;

 out:
  lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
  return ret;
}