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Programming
Multiple instances of pthread
Post 302644837 by clerew on Tuesday 22nd of May 2012 01:17:40 PM
05-22-2012
Multiple instances of pthread
Indeed, but the pthreads in my example were created as detached (I showed a parameter '&detach' which was intended to give a strong hint to that effect).
And I agree that pthread_kill has to be used with caution, but in my case the threads were all 'sleep'ing, so I killed them with SIGALRM and they woke up and proceeded on their way, which was to kill themselves.
But you have not answered my main question, which was what happens (or is supposed to happen) if you create another thread on the same tid variable before it has died. It may be (indeed probably is) bad practice, but bad practice (aka s**t) happens, and the pthread system offers no help in avoiding it.
And if I need to know whether the thread on some tid is still running, how can I tell? Do I have to create some sufficiently global variable and keep track of it myself (which is what I have done) is is there some way I can ask?
It seems that what I need to do is discover whether a thread is still running on the tid, and then either arrane to kill it, or else to persuade the existing thread to take on new responsibilities. When I first wrote this code, I did not consider this possibility and it worked fine until things started to happen too faat
.
And I agree that pthread_kill has to be used with caution, but in my case the threads were all 'sleep'ing, so I killed them with SIGALRM and they woke up and proceeded on their way, which was to kill themselves.
But you have not answered my main question, which was what happens (or is supposed to happen) if you create another thread on the same tid variable before it has died. It may be (indeed probably is) bad practice, but bad practice (aka s**t) happens, and the pthread system offers no help in avoiding it.
And if I need to know whether the thread on some tid is still running, how can I tell? Do I have to create some sufficiently global variable and keep track of it myself (which is what I have done) is is there some way I can ask?
It seems that what I need to do is discover whether a thread is still running on the tid, and then either arrane to kill it, or else to persuade the existing thread to take on new responsibilities. When I first wrote this code, I did not consider this possibility and it worked fine until things started to happen too faat
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LEARN ABOUT MOJAVE
tgkill
TKILL(2) Linux Programmer's Manual TKILL(2) NAME
tkill, tgkill - send a signal to a thread SYNOPSIS
int tkill(int tid, int sig); int tgkill(int tgid, int tid, int sig); Note: There are no glibc wrappers for these system calls; see NOTES. DESCRIPTION
tgkill() sends the signal sig to the thread with the thread ID tid in the thread group tgid. (By contrast, kill(2) can be used to send a signal only to a process (i.e., thread group) as a whole, and the signal will be delivered to an arbitrary thread within that process.) tkill() is an obsolete predecessor to tgkill(). It allows only the target thread ID to be specified, which may result in the wrong thread being signaled if a thread terminates and its thread ID is recycled. Avoid using this system call. These are the raw system call interfaces, meant for internal thread library use. RETURN VALUE
On success, zero is returned. On error, -1 is returned, and errno is set appropriately. ERRORS
EINVAL An invalid thread ID, thread group ID, or signal was specified. EPERM Permission denied. For the required permissions, see kill(2). ESRCH No process with the specified thread ID (and thread group ID) exists. EAGAIN The RLIMIT_SIGPENDING resource limit was reached and sig is a real-time signal. EAGAIN Insufficient kernel memory was available and sig is a real-time signal. VERSIONS
tkill() is supported since Linux 2.4.19 / 2.5.4. tgkill() was added in Linux 2.5.75. CONFORMING TO
tkill() and tgkill() are Linux-specific and should not be used in programs that are intended to be portable. NOTES
See the description of CLONE_THREAD in clone(2) for an explanation of thread groups. Glibc does not provide wrappers for these system calls; call them using syscall(2). SEE ALSO
clone(2), gettid(2), kill(2), rt_sigqueueinfo(2) COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. Linux 2017-09-15 TKILL(2)