core: locking - added recursive lock apis

- new structure rec_lock_t
- api functions:
	- rec_lock_alloc()
	- rec_lock_init(rlock)
	- rec_lock_destroy(rlock)
	- rec_lock_dealloc(rlock)
	- rec_lock_get(rlock)
	- rec_lock_release(rlock)

locking.c

@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2016 kamailio.org
+ *
+ * This file is part of Kamailio, a free SIP server.
+ *
+ * Kamailio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version
+ *
+ * Kamailio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "mem/shm.h"
+
+#include "locking.h"
+
+/**
+ *
+ */
+rec_lock_t* rec_lock_alloc()
+{
+	return shm_malloc(sizeof(rec_lock_t));
+}
+
+/**
+ *
+ */
+rec_lock_t* rec_lock_init(rec_lock_t* rlock)
+{
+	memset(rlock, 0, sizeof(rec_lock_t));
+	if(lock_init(&rlock->lock)<0) {
+		return NULL;
+	}
+	return rlock;
+}
+
+/**
+ *
+ */
+void rec_lock_destroy(rec_lock_t* rlock)
+{
+	lock_destroy(&rlock->lock);
+	memset(rlock, 0, sizeof(rec_lock_t));
+}
+
+/**
+ *
+ */
+void rec_lock_dealloc(rec_lock_t* rlock)
+{
+	shm_free(rlock);
+}
+
+/**
+ *
+ */
+void rec_lock_get(rec_lock_t* rlock)
+{
+	int mypid;
+
+	mypid = my_pid();
+	if (likely(atomic_get(&rlock->locker_pid) != mypid)) {
+		lock_get(&rlock->lock);
+		atomic_set(&rlock->locker_pid, mypid);
+	} else {
+		/* locked within the same process that executed us */
+		rlock->rec_lock_level++;
+	}
+}
+
+/**
+ *
+ */
+void rec_lock_release(rec_lock_t* rlock)
+{
+	if (likely(rlock->rec_lock_level == 0)) {
+		atomic_set(&rlock->locker_pid, 0);
+		lock_release(&rlock->lock);
+	} else  {
+		/* recursive locked => decrease lock count */
+		rlock->rec_lock_level--;
+	}
+}

locking.h

@@ -14,8 +14,8 @@
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License 
- * along with this program; if not, write to the Free Software 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */
 
@@ -38,7 +38,7 @@ Implements (in lock_ops.h & lock_alloc.h):
 	void    lock_dealloc(gen_lock_t* lock);  - deallocates the lock's shared m.
 	void    lock_get(gen_lock_t* lock);      - lock (mutex down)
 	void    lock_release(gen_lock_t* lock);  - unlock (mutex up)
-	
+
 	lock sets:
 	----------
 	type: gen_lock_set_t
@@ -49,7 +49,17 @@ Implements (in lock_ops.h & lock_alloc.h):
 	void lock_set_get(gen_lock_set_t* s, int i);     - locks sem i from the set
 	void lock_set_release(gen_lock_set_t* s, int i)  - unlocks sem i from the set
 
-WARNING: - lock_set_init may fail for large number of sems (e.g. sysv). 
+	recursive locks:
+	-------------
+	type: rec_lock_t
+	rec_lock_t* rec_lock_alloc();                - allocates a lock in shared mem.
+	rec_lock_t* rec_lock_init(rec_lock_t* lock); - inits the lock
+	void    rec_lock_destroy(rec_lock_t* lock);  - removes the lock (e.g sysv rmid)
+	void    rec_lock_dealloc(rec_lock_t* lock);  - deallocates the lock's shared m.
+	void    rec_lock_get(rec_lock_t* lock);      - lock (mutex down)
+	void    rec_lock_release(rec_lock_t* lock);  - unlock (mutex up)
+
+WARNING: - lock_set_init may fail for large number of sems (e.g. sysv).
          - signals are not treated! (some locks are "awakened" by the signals)
 */
 
@@ -58,6 +68,20 @@ WARNING: - lock_set_init may fail for large number of sems (e.g. sysv).
 
 /* the order is important */
 #include "lock_ops.h"
-#include "lock_alloc.h" 
+#include "lock_alloc.h"
+#include "atomic_ops.h"
+
+typedef struct rec_lock {
+	gen_lock_t lock;     /* mutex to access items in the slot */
+	atomic_t locker_pid; /* pid of the process that holds the lock */
+	int rec_lock_level;  /* recursive lock count */
+} rec_lock_t;
+
+rec_lock_t* rec_lock_alloc();
+rec_lock_t* rec_lock_init(rec_lock_t* lock);
+void rec_lock_destroy(rec_lock_t* lock);
+void rec_lock_dealloc(rec_lock_t* lock);
+void rec_lock_get(rec_lock_t* lock);
+void rec_lock_release(rec_lock_t* lock);
 
 #endif