tgkill(2)

1tkill(2)                      System Calls Manual                     tkill(2)
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NAME

6       tkill, tgkill - send a signal to a thread
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <signal.h>           /* Definition of SIG* constants */
13       #include <sys/syscall.h>      /* Definition of SYS_* constants */
14       #include <unistd.h>
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16       [[deprecated]] int syscall(SYS_tkill, pid_t tid, int sig);
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18       #include <signal.h>
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20       int tgkill(pid_t tgid, pid_t tid, int sig);
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22       Note:  glibc  provides no wrapper for tkill(), necessitating the use of
23       syscall(2).
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DESCRIPTION

26       tgkill() sends the signal sig to the thread with the thread ID  tid  in
27       the  thread  group  tgid.   (By contrast, kill(2) can be used to send a
28       signal only to a process (i.e., thread group) as a whole, and the  sig‐
29       nal will be delivered to an arbitrary thread within that process.)
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31       tkill()  is  an  obsolete  predecessor to tgkill().  It allows only the
32       target thread ID to be specified, which may result in the wrong  thread
33       being  signaled  if  a thread terminates and its thread ID is recycled.
34       Avoid using this system call.
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36       These are the raw system call interfaces, meant for internal thread li‐
37       brary use.
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RETURN VALUE

40       On  success,  zero is returned.  On error, -1 is returned, and errno is
41       set to indicate the error.
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ERRORS

44       EAGAIN The RLIMIT_SIGPENDING resource limit was reached and  sig  is  a
45              real-time signal.
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47       EAGAIN Insufficient  kernel memory was available and sig is a real-time
48              signal.
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50       EINVAL An invalid thread ID, thread group ID, or signal was specified.
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52       EPERM  Permission denied.  For the required permissions, see kill(2).
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54       ESRCH  No process with the specified thread ID (and  thread  group  ID)
55              exists.
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STANDARDS

58       Linux.
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HISTORY

61       tkill()
62              Linux 2.4.19 / 2.5.4.
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64       tgkill()
65              Linux 2.5.75, glibc 2.30.
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NOTES

68       See  the  description of CLONE_THREAD in clone(2) for an explanation of
69       thread groups.
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