userspace: librarize (and used twice) the previous commit

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

userspace/libwr/include/libwr/shmem.h

@@ -44,6 +44,9 @@ struct wrs_shm_head {
 void *wrs_shm_get(enum wrs_shm_name name_id, char *name, unsigned long flags);
 int wrs_shm_put(void *headptr);
 
+/* A reader may wait for the writer (polling on version field) */
+void wrs_shm_wait(void *headptr, int msec_step, int retries, FILE *msg);
+
 /* The writer can allocate structures that live in the area itself */
 void *wrs_shm_alloc(void *headptr, size_t size);
 

userspace/libwr/shmem.c

@@ -113,6 +113,23 @@ int wrs_shm_put(void *headptr)
 	return 0;
 }
 
+/* A reader may wait for the writer (polling on version field) */
+void wrs_shm_wait(void *headptr, int msec_step, int retries, FILE *msg)
+{
+	struct wrs_shm_head *head = headptr;
+	int i;
+
+	for (i = 0; i < retries && !head->version; i++) {
+		if (!i && msg)
+			fprintf(msg, "Waiting for my peer...");
+		if (msg)
+			fprintf(stderr, ".");
+		usleep(1000 * msec_step);
+	}
+	if (i && msg)
+		fprintf(msg, "\n");
+}
+
 /* The writer can allocate structures that live in the area itself */
 void *wrs_shm_alloc(void *headptr, size_t size)
 {

userspace/snmpd/snmp_shmem.c

@@ -26,6 +26,8 @@ static void init_shm_hal(void)
 		snmp_log(LOG_ERR, "unable to open shm for HAL!\n");
 		exit(-1);
 	}
+	wrs_shm_wait(hal_head, 500 /* ms */, 20, NULL);
+
 	/* check hal's shm version */
 	if (hal_head->version != HAL_SHMEM_VERSION) {
 		snmp_log(LOG_ERR, "unknown hal's shm version %i "

userspace/tools/wr_mon.c

@@ -99,23 +99,13 @@ void ppsi_connect_minipc()
 void init_shm(void)
 {
 	struct hal_shmem_header *h;
-	int retr, maxretr = 15;
 
 	hal_head = wrs_shm_get(wrs_shm_hal, "", WRS_SHM_READ);
 	if (!hal_head) {
 		fprintf(stderr, "unable to open shm for HAL!\n");
 		exit(1);
 	}
-	for (retr = 0; retr < maxretr && !hal_head->version; retr++) {
-		if (!retr)
-			fprintf(stderr, "Waiting for HAL..");
-		fprintf(stderr, ".");
-		sleep(1);
-	}
-	if (retr)
-		fprintf(stderr, "\n");
-
-	/* check hal's shm version */
+	wrs_shm_wait(hal_head, 500 /* ms */, 20, stderr);
 	if (hal_head->version != HAL_SHMEM_VERSION) {
 		fprintf(stderr, "wr_mon: unknown HAL's shm version %i "
 			"(known is %i)\n",
@@ -146,6 +136,7 @@ void init_shm(void)
 		fprintf(stderr, "unable to open shm for PPSI!\n");
 		exit(1);
 	}
+	wrs_shm_wait(ppsi_head, 500 /* ms */, 20, stderr);
 
 	/* check hal's shm version */
 	if (ppsi_head->version != WRS_PPSI_SHMEM_VERSION) {