mq_notify: use semaphore instead of barrier to sync args consumption

semaphores are a much lighter primitive, and more idiomatic with
current usage in the code base.

diff --git a/src/mq/mq_notify.c b/src/mq/mq_notify.c
index 221591c..a42888d 100644 (file)
--- a/src/mq/mq_notify.c
+++ b/src/mq/mq_notify.c
@@ -4,10 +4,11 @@
 #include <sys/socket.h>
 #include <signal.h>
 #include <unistd.h>
+#include <semaphore.h>
 #include "syscall.h"
 
 struct args {
-       pthread_barrier_t barrier;
+       sem_t sem;
        int sock;
        const struct sigevent *sev;
 };
@@ -21,7 +22,7 @@ static void *start(void *p)
        void (*func)(union sigval) = args->sev->sigev_notify_function;
        union sigval val = args->sev->sigev_value;
 
-       pthread_barrier_wait(&args->barrier);
+       sem_post(&args->sem);
        n = recv(s, buf, sizeof(buf), MSG_NOSIGNAL|MSG_WAITALL);
        close(s);
        if (n==sizeof buf && buf[sizeof buf - 1] == 1)
@@ -37,6 +38,7 @@ int mq_notify(mqd_t mqd, const struct sigevent *sev)
        int s;
        struct sigevent sev2;
        static const char zeros[32];
+       int cs;
 
        if (!sev || sev->sigev_notify != SIGEV_THREAD)
                return syscall(SYS_mq_notify, mqd, sev);
@@ -48,7 +50,7 @@ int mq_notify(mqd_t mqd, const struct sigevent *sev)
        if (sev->sigev_notify_attributes) attr = *sev->sigev_notify_attributes;
        else pthread_attr_init(&attr);
        pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-       pthread_barrier_init(&args.barrier, 0, 2);
+       sem_init(&args.sem, 0, 0);
 
        if (pthread_create(&td, &attr, start, &args)) {
                __syscall(SYS_close, s);
@@ -56,8 +58,10 @@ int mq_notify(mqd_t mqd, const struct sigevent *sev)
                return -1;
        }
 
-       pthread_barrier_wait(&args.barrier);
-       pthread_barrier_destroy(&args.barrier);
+       pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+       sem_wait(&args.sem);
+       pthread_setcancelstate(cs, 0);
+       sem_destroy(&args.sem);
 
        sev2.sigev_notify = SIGEV_THREAD;
        sev2.sigev_signo = s;