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1-Sending unix signals is only possible to a processes, or it is also possible to send signals to threads?

2-Is it possible to send the tid of a thread to a kernel module? How?

3-In what way the kernel module can find the tid of a thread, to send a signal?

4-the thread will have a handler that will run on each signal. If each handler corresponds to a signal, are there any race conditions? Can communicate a signal to all threads? What happens if all access the handler at a time?

eduardosufan
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    See, for example, http://linux.die.net/man/3/pthread_kill and http://infohost.nmt.edu/~eweiss/222_book/222_book/0201433079/ch12lev1sec8.html – lurker Sep 05 '13 at 20:15
  • Specify environment (threads can be implemented differently). Maybe add kernel tag? – zoska Sep 17 '13 at 13:07

1 Answers1

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Ad.1 From where do you want to send a signal? You can use kill() to send signal to process and pthread_kill() to send it to thread (but only from process which created thread).

Ad.3. While handling one signal, other pending signals will be queued, so there will be no race conditions. But you need to set non local variables used in handler to atomic (so when interrupt comes setting this variable will not be interrupted) and check which functions are handler safe.

About signals and threads - signal usually comes directly to process (only with pthread_kill you can send signal to thread from user space). If you have multithreaded process and none of thread has this signal blocked, then signal will come to random thread (the one which is running exactly when signal comes). If you block all threads but one, then signal will come to only this one thread.

zoska
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