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Old 07-28-2021, 05:28 AM   #1
s0n1c
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Interrupt source


Hello forum,

I'm pretty new to this kind of programming and need some help:

I generate an interrupt on raspbian using struct itimerval for the timer and struct sigaction (see https://man7.org/linux/man-pages/man2/sigaction.2.html) for the signal generating an interrupt. The member sigaction.sa_handler seems to be a pointer to a function, some kind of interrupt service routine like used on Arduinos. The function needs one integer as input and I wonder what this is. Can anyone tell me if there is a list or something to determine the exact source of the interrupt?

Regards
s0n1c
 
Old 07-28-2021, 06:25 AM   #2
NevemTeve
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In 'struct sigaction' you can use either 'sa_handler' or 'sa_sigaction', but not both of them. Also you have to use flag SA_SIGINFO in field sa_flags accordingly.
Example1:
Code:
    static void handler (int signo) {
        [I only have 'signo']
    }

    int main (void) {
        struct sigaction siga;

        memset (&siga, 0, sizeof siga);
        siga.sa_handler= handler;

        sigaction (SIGsomething, &siga, NULL);
        ...
    }
Example2:
Code:
    static void handler3 (int signo, siginfo_t *info, void *ucontext) {
        [I have 'signo' and 'info', also 'ucontext' whatever it is]
    }

    int main (void) {
        struct sigaction siga;

        memset (&siga, 0, sizeof siga);
        siga.sa_sigaction= handler3;
        siga.sa_flags |= SA_SIGINFO;

        sigaction (SIGsomething, &siga, NULL);
        ...
    }
 
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Old 07-28-2021, 06:28 AM   #3
GazL
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The int passed as an argument to a signal handler is the signal number (i.e. type) that caused it to be invoked. If a signal handler is only attached to a single signal, then it's pretty much redundant information.

The sigaction(3) man-page documents this, and you can find the signal numbers on signal(7).
 
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Old 07-28-2021, 09:29 AM   #4
GazL
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I've never had need of the fancier SA_SIGINFO variant, but perhaps one day a use-case will present itself.
 
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Old 07-29-2021, 12:53 AM   #5
s0n1c
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Thank you, this solved my problem!!!
 
2 members found this post helpful.
  


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