![]() ![]() Sends a signal to a specified process, to all members of a specified process group, or to all processes on the system. Sending a signal The following system calls and library functions allow the caller to send a signal: Reset to the default the dispositions of ignored signals are left unchanged. During an execve(2), the dispositions of handled signals are The signal disposition is a per-process attribute: in a multithreaded application, the disposition of a particular signal is the same for all threads.Ī child created via fork(2) inherits a copy of its parent's signal dispositions. It is possible to arrange that the signal handler uses anĪlternate stack see sigaltstack(2) for a discussion of how to do this and when it might be useful.) ![]() (By default, the signal handler is invoked on the normal process stack. Perform the default action ignore the signal or catch the signal with a signal handler, a programmer-defined function that is automatically invoked Handler see signal(2) for details.) Using these system calls, a process can elect one of the following behaviors to occur on delivery of the signal: (The latter is less portable when establishing a signal The entries in the "Action" column of the tables below specify the default disposition for each signal, as follows:ĭefault action is to terminate the process.ĭefault action is to terminate the process and dump core (see core(5)).ĭefault action is to continue the process if it is currently stopped.Ī process can change the disposition of a signal using sigaction(2) or signal(2). Signal dispositions Each signal has a current disposition, which determines how the process behaves when it is delivered the signal. I have set SA_RESTART flag so if function call is interrupted by signal, function will be restarted after signal handler is finished.Linux supports both POSIX reliable signals (hereinafter "standard signals") and POSIX real-time signals. I'm also not sure if I need to check return value from sem_wait() and sem_post(). Thread will have to wait after one variable change for a signal handler to release semaphore to continue processing. What if one of my variable is changed more than once in a second ? - my signal handler goes on every second. You say I can only sem_post() inside a signal handler and only sem_wait() inside a threads? I have semaphores implemented on many places inside thread. In your current implementation sem_wait and sem_post are probably failing and returning EINTR at least sometimes, which will cause your semaphore to be off by one and lock the program solid. You might be able to create a more signal-safe arrangement wherein the interrupt handler only posts and the thread only waits.Īlso, it's a good idea to check the return value of these things. This code can be found both in signal handler and in thread.Ĭorrect. Below is an example of use reinitialization of protected variable. I'm using same counters inside signal handler! Semaphores are in both locations. All counter are protected with semaphores (semCounter). Inside a second thread (secondThread) I have multiple math operation with time counters. Pthread_create(&thread2, NULL, secondThread, NULL) ![]() Pthread_create(&thread1, NULL, firstThread, NULL) read files containing parameters of remote devices
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