1  /* Copyright (C) 2002-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <setjmp.h>
      19  #include <stdlib.h>
      20  #include "pthreadP.h"
      21  #include <futex-internal.h>
      22  
      23  
      24  /* The next two functions are similar to pthread_setcanceltype() but
      25     more specialized for the use in the cancelable functions like write().
      26     They do not need to check parameters etc.  These functions must be
      27     AS-safe, with the exception of the actual cancellation, because they
      28     are called by wrappers around AS-safe functions like write().*/
      29  int
      30  __pthread_enable_asynccancel (void)
      31  {
      32    struct pthread *self = THREAD_SELF;
      33    int oldval = atomic_load_relaxed (&self->cancelhandling);
      34  
      35    while (1)
      36      {
      37        int newval = oldval | CANCELTYPE_BITMASK;
      38  
      39        if (newval == oldval)
      40  	break;
      41  
      42        if (atomic_compare_exchange_weak_acquire (&self->cancelhandling,
      43  						&oldval, newval))
      44  	{
      45  	  if (cancel_enabled_and_canceled_and_async (newval))
      46  	    {
      47  	      self->result = PTHREAD_CANCELED;
      48  	      __do_cancel ();
      49  	    }
      50  
      51  	  break;
      52  	}
      53      }
      54  
      55    return oldval;
      56  }
      57  libc_hidden_def (__pthread_enable_asynccancel)
      58  
      59  /* See the comment for __pthread_enable_asynccancel regarding
      60     the AS-safety of this function.  */
      61  void
      62  __pthread_disable_asynccancel (int oldtype)
      63  {
      64    /* If asynchronous cancellation was enabled before we do not have
      65       anything to do.  */
      66    if (oldtype & CANCELTYPE_BITMASK)
      67      return;
      68  
      69    struct pthread *self = THREAD_SELF;
      70    int newval;
      71    int oldval = atomic_load_relaxed (&self->cancelhandling);
      72    do
      73      {
      74        newval = oldval & ~CANCELTYPE_BITMASK;
      75      }
      76    while (!atomic_compare_exchange_weak_acquire (&self->cancelhandling,
      77  						&oldval, newval));
      78  
      79    /* We cannot return when we are being canceled.  Upon return the
      80       thread might be things which would have to be undone.  The
      81       following loop should loop until the cancellation signal is
      82       delivered.  */
      83    while (__glibc_unlikely ((newval & (CANCELING_BITMASK | CANCELED_BITMASK))
      84  			   == CANCELING_BITMASK))
      85      {
      86        futex_wait_simple ((unsigned int *) &self->cancelhandling, newval,
      87  			 FUTEX_PRIVATE);
      88        newval = atomic_load_relaxed (&self->cancelhandling);
      89      }
      90  }
      91  libc_hidden_def (__pthread_disable_asynccancel)