nptl/pthread_kill.c

   1 /* Send a signal to a specific pthread.  Stub version.
   2    Copyright (C) 2014-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <libc-lock.h>
  20 #include <unistd.h>
  21 #include <pthreadP.h>
  22 #include <shlib-compat.h>
  23
  24 /* Sends SIGNO to THREADID.  If the thread is about to exit or has
  25    already exited on the kernel side, return NO_TID.  Otherwise return
  26    0 or an error code. */
  27 static int
  28 __pthread_kill_implementation (pthread_t threadid, int signo, int no_tid)
  29 {
  30   struct pthread *pd = (struct pthread *) threadid;
  31   if (pd == THREAD_SELF)
  32     {
  33       /* Use the actual TID from the kernel, so that it refers to the
  34          current thread even if called after vfork.  There is no
  35          signal blocking in this case, so that the signal is delivered
  36          immediately, before __pthread_kill_internal returns: a signal
  37          sent to the thread itself needs to be delivered
  38          synchronously.  (It is unclear if Linux guarantees the
  39          delivery of all pending signals after unblocking in the code
  40          below.  POSIX only guarantees delivery of a single signal,
  41          which may not be the right one.)  */
  42       pid_t tid = INTERNAL_SYSCALL_CALL (gettid);
  43       int ret = INTERNAL_SYSCALL_CALL (tgkill, __getpid (), tid, signo);
  44       return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
  45     }
  46
  47   /* Block all signals, as required by pd->exit_lock.  */
  48   sigset_t old_mask;
  49   __libc_signal_block_all (&old_mask);
  50   __libc_lock_lock (pd->exit_lock);
  51
  52   int ret;
  53   if (pd->exiting)
  54     /* The thread is about to exit (or has exited).  Sending the
  55        signal is either not observable (the target thread has already
  56        blocked signals at this point), or it will fail, or it might be
  57        delivered to a new, unrelated thread that has reused the TID.
  58        So do not actually send the signal.  */
  59     ret = no_tid;
  60   else
  61     {
  62       ret = INTERNAL_SYSCALL_CALL (tgkill, __getpid (), pd->tid, signo);
  63       ret = INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
  64     }
  65
  66   __libc_lock_unlock (pd->exit_lock);
  67   __libc_signal_restore_set (&old_mask);
  68
  69   return ret;
  70 }
  71
  72 int
  73 __pthread_kill_internal (pthread_t threadid, int signo)
  74 {
  75   /* Do not report an error in the no-tid case because the threadid
  76      argument is still valid (the thread ID lifetime has not ended),
  77      and ESRCH (for example) would be misleading.  */
  78   return __pthread_kill_implementation (threadid, signo, 0);
  79 }
  80
  81 int
  82 __pthread_kill (pthread_t threadid, int signo)
  83 {
  84   /* Disallow sending the signal we use for cancellation, timers,
  85      for the setxid implementation.  */
  86   if (__is_internal_signal (signo))
  87     return EINVAL;
  88
  89   return __pthread_kill_internal (threadid, signo);
  90 }
  91
  92 /* Some architectures (for instance arm) might pull raise through libgcc, so
  93    avoid the symbol version if it ends up being used on ld.so.  */
  94 #if !IS_IN(rtld)
  95 libc_hidden_def (__pthread_kill)
  96 versioned_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_34);
  97
  98 # if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
  99 /* Variant which returns ESRCH in the no-TID case, for backwards
 100    compatibility.  */
 101 int
 102 attribute_compat_text_section
 103 __pthread_kill_esrch (pthread_t threadid, int signo)
 104 {
 105   if (__is_internal_signal (signo))
 106     return EINVAL;
 107
 108   return __pthread_kill_implementation (threadid, signo, ESRCH);
 109 }
 110 compat_symbol (libc, __pthread_kill_esrch, pthread_kill, GLIBC_2_0);
 111 # endif
 112 #endif