#include <pthread.h>
#include <signal.h>
int pthread_sigmask(int how, const sigset_t *set,
sigset_t *oset);
Service Program Name: QP0WPTHRThe pthread_sigmask() function examines or modifies the signal blocking mask for the current thread.
The signals SIGKILL or SIGStop cannot be blocked. Any attempt to use pthread_sigmask() to block these signals is simply ignored, and no error is returned.
SIGFPE, SIGILL, and SIGSEGV signals that are not artificially generated by kill(), pthread_kill() or raise() (that is, were generated by the system as a result of a hardware or software exception) are not blocked.
If there are any pending unblocked signals after pthread_sigmask() has changed the signal mask, at least one of those signals is delivered to the process before pthread_sigmask() returns.
If pthread_sigmask() fails, the signal mask of the thread is not changed.
The possible values for how, which are defined in the <signal.h> header file, are as follows:
Indicates that the set of signals given by set should be blocked, in addition to the set currently being blocked
Indicates that the set of signals given by set should not be blocked. These signals are removed from the current set of signals being blocked
Indicates that the set of signals given by set should replace the old set of signals being blocked
The set parameter points to a signal set that contains the new signals that should be blocked or unblocked (depending on the value of how), or it points to the new signal mask if the value of how is SIG_SETMASK. If set is a NULL pointer, the set of blocked signals is not changed. If set is NULL, the value of how is ignored.
The signal set manipulation functions (sigemptyset(), sigfillset(), sigaddset(), and sigdelset()) must be used to establish the new signal set pointed to by set.
The pthread_sigmask() function determines the current signal set and returns this information in *oset. If set is NULL, oset returns the current set of signals being blocked. When set is not NULL, the set of signals pointed to by oset is the previous set.
None.
If pthread_sigmask() was not successful, the error condition returned usually indicates one of the following errors. Under some conditions, the value returned could indicate an error other than those listed here.
The value specified for the argument is not correct.
The process is not enabled for signals.
See Code disclaimer information for information pertaining to code examples.
#define _MULTI_THREADED
#include <pthread.h>
#include <stdio.h>
#include <signal.h>
#include "check.h"
#define NUMTHREADS 3
void sighand(int signo);
void *threadfunc(void *parm)
{
pthread_t self = pthread_self();
pthread_id_np_t tid;
int rc;
pthread_getunique_np(&self, &tid);
printf("Thread 0x%.8x %.8x entered\n", tid);
errno = 0;
rc = sleep(30);
if (rc != 0 && errno == EINTR) {
printf("Thread 0x%.8x %.8x got a signal delivered to it\n",
tid);
return NULL;
}
printf("Thread 0x%.8x %.8x did not get expected results! rc=%d, errno=%d\n",
tid, rc, errno);
return NULL;
}
void *threadmasked(void *parm)
{
pthread_t self = pthread_self();
pthread_id_np_t tid;
sigset_t mask;
int rc;
pthread_getunique_np(&self, &tid);
printf("Masked thread 0x%.8x %.8x entered\n", tid);
sigfillset(&mask); /* Mask all allowed signals */
rc = pthread_sigmask(SIG_BLOCK, &mask, NULL);
checkResults("pthread_sigmask()\n", rc);
errno = 0;
rc = sleep(15);
if (rc != 0) {
printf("Masked thread 0x%.8x %.8x did not get expected results! "
"rc=%d, errno=%d\n",
tid, rc, errno);
return NULL;
}
printf("Masked thread 0x%.8x %.8x completed masked work\n",
tid);
return NULL;
}
int main(int argc, char **argv)
{
int rc;
int i;
struct sigaction actions;
pthread_t threads[NUMTHREADS];
pthread_t maskedthreads[NUMTHREADS];
printf("Enter Testcase - %s\n", argv[0]);
printf("Set up the alarm handler for the process\n");
memset(&actions, 0, sizeof(actions));
sigemptyset(&actions.sa_mask);
actions.sa_flags = 0;
actions.sa_handler = sighand;
rc = sigaction(SIGALRM,&actions,NULL);
checkResults("sigaction\n", rc);
printf("Create masked and unmasked threads\n");
for(i=0; i<NUMTHREADS; ++i) {
rc = pthread_create(&threads[i], NULL, threadfunc, NULL);
checkResults("pthread_create()\n", rc);
rc = pthread_create(&maskedthreads[i], NULL, threadmasked, NULL);
checkResults("pthread_create()\n", rc);
}
sleep(3);
printf("Send a signal to masked and unmasked threads\n");
for(i=0; i<NUMTHREADS; ++i) {
rc = pthread_kill(threads[i], SIGALRM);
checkResults("pthread_kill()\n", rc);
rc = pthread_kill(maskedthreads[i], SIGALRM);
checkResults("pthread_kill()\n", rc);
}
printf("Wait for masked and unmasked threads to complete\n");
for(i=0; i<NUMTHREADS; ++i) {
rc = pthread_join(threads[i], NULL);
checkResults("pthread_join()\n", rc);
rc = pthread_join(maskedthreads[i], NULL);
checkResults("pthread_join()\n", rc);
}
printf("Main completed\n");
return 0;
}
void sighand(int signo)
{
pthread_t self = pthread_self();
pthread_id_np_t tid;
pthread_getunique_np(&self, &tid);
printf("Thread 0x%.8x %.8x in signal handler\n",
tid);
return;
}
Output:
Thread 0x00000000 0000000d entered Masked thread 0x00000000 0000000a entered Thread 0x00000000 00000009 entered Thread 0x00000000 0000000b entered Masked thread 0x00000000 0000000e entered Masked thread 0x00000000 0000000c entered Send a signal to masked and unmasked threads Wait for masked and unmasked threads to complete Thread 0x00000000 00000009 in signal handler Thread 0x00000000 00000009 got a signal delivered to it Thread 0x00000000 0000000b in signal handler Thread 0x00000000 0000000b got a signal delivered to it Thread 0x00000000 0000000d in signal handler Thread 0x00000000 0000000d got a signal delivered to it Masked thread 0x00000000 0000000a completed masked work Masked thread 0x00000000 0000000e completed masked work Masked thread 0x00000000 0000000c completed masked work Main completed
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