nptl/pthread_gettid_np.c


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/* Get the Linux TID from a pthread_t handle.
   Copyright (C) 2025-2026 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; see the file COPYING.LIB.  If
   not, see <https://www.gnu.org/licenses/>.  */

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

pid_t
pthread_gettid_np (pthread_t threadid)
{
  /* The kernel may concurrently set this field.  */
  pid_t tid = atomic_load_relaxed (&((struct pthread *) threadid)->tid);
  if (tid <= 0)
    return -1;
  return tid;
}