9. Blocking Signals in Critical Sections

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9. Blocking Signals in Critical Sections

Why is it important to block signals in critical sections of code? Provide an example of how to block SIGINT during a critical section to ensure the integrity of shared data.

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Blocking signals in critical section of code is essential as certain operations need to be completed without any interruption. For example, when modifying data structures or performing atomic operations, blocking signals can prevent race conditions and ensure data integrity. For e.g.:

#include <stdio.h>

#include <stdlib.h>

#include <signal.h>

#include <unistd.h>

volatile sig_atomic_t counter = 0;

void handle_signal(int sig)

{

printf("Caught signal %d, counter = %d\n", sig, counter);

}

void critical_section()

{

sigset_t mask, oldmask;

sigemptyset(&mask);

sigaddset(&mask, SIGINT);

if (sigprocmask(SIG_BLOCK, &mask, &oldmask) == -1)

{

perror("sigprocmask");

exit(EXIT_FAILURE);

}

printf("Entering critical section\n");

for (int i = 0; i < 5; ++i)

{

++counter;

printf("Counter = %d\n", counter);

sleep(1);

}

printf("Leaving critical section\n");

if (sigprocmask(SIG_SETMASK, &oldmask, NULL) == -1)

{

perror("sigprocmask");

exit(EXIT_FAILURE);

}

int main()

{

struct sigaction sa;

sa.sa_handler = handle_signal;

sa.sa_flags = 0; // No flags

sigemptyset(&sa.sa_mask);

// Set up the signal handler for SIGINT

if (sigaction(SIGINT, &sa, NULL) == -1)

{

perror("sigaction");

exit(EXIT_FAILURE);

}

// Loop indefinitely

while (1)

{

critical_section();

sleep(2); // Sleep outside of the critical section

}

return 0;

}

9. Blocking Signals in Critical Sections

9. Blocking Signals in Critical Sections

Why is it important to block signals in critical sections of code? Provide an example of how to block SIGINT during a critical section to ensure the integrity of shared data.

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