3 files changed, 69 insertions, 30 deletions
diff --git a/libnetdata/locks/README.md b/libnetdata/locks/README.md
index 9ac96a8f6..9132edc43 100644
--- a/libnetdata/locks/README.md
+++ b/libnetdata/locks/README.md
@@ -49,7 +49,7 @@ The library maintains a linked-list of all the lock holders (one entry per threa
 If any call is expected to pause the caller (ie the caller is attempting a read lock while there is a write lock in place and vice versa), the library will log something like this:
 
 ```
-RW_LOCK ON LOCK 0x0x5651c9fcce20: 4190039 'HEALTH' (function init_pending_foreach_alarms() 661@health/health.c) WANTS a 'W' lock (while holding 1 rwlocks and 1 mutexes).
+RW_LOCK ON LOCK 0x0x5651c9fcce20: 4190039 'HEALTH' (function health_execute_pending_updates() 661@health/health.c) WANTS a 'W' lock (while holding 1 rwlocks and 1 mutexes).
 There are 7 readers and 0 writers are holding the lock:
      => 1: RW_LOCK: process 4190091 'WEB_SERVER[static14]' (function web_client_api_request_v1_data() 526@web/api/web_api_v1.c) is having 1 'R' lock for 709847 usec.
      => 2: RW_LOCK: process 4190079 'WEB_SERVER[static6]' (function web_client_api_request_v1_data() 526@web/api/web_api_v1.c) is having 1 'R' lock for 709869 usec.
@@ -63,9 +63,9 @@ There are 7 readers and 0 writers are holding the lock:
 And each of the above is paired with a `GOT` log, like this:
 
 ```
-RW_LOCK ON LOCK 0x0x5651c9fcce20: 4190039 'HEALTH' (function init_pending_foreach_alarms() 661@health/health.c) GOT a 'W' lock (while holding 2 rwlocks and 1 mutexes).
+RW_LOCK ON LOCK 0x0x5651c9fcce20: 4190039 'HEALTH' (function health_execute_pending_updates() 661@health/health.c) GOT a 'W' lock (while holding 2 rwlocks and 1 mutexes).
 There are 0 readers and 1 writers are holding the lock:
-     => 1: RW_LOCK: process 4190039 'HEALTH' (function init_pending_foreach_alarms() 661@health/health.c) is having 1 'W' lock for 36 usec.
+     => 1: RW_LOCK: process 4190039 'HEALTH' (function health_execute_pending_updates() 661@health/health.c) is having 1 'W' lock for 36 usec.
 ```
 
 Keep in mind that the lock and log are not atomic. The list of callers is indicative (and sometimes just empty because the original holders of the lock, unlocked it until we had the chance to print their names).
diff --git a/libnetdata/locks/locks.c b/libnetdata/locks/locks.c
index 8b5348678..f7191be52 100644
--- a/libnetdata/locks/locks.c
+++ b/libnetdata/locks/locks.c
@@ -278,6 +278,37 @@ int __netdata_rwlock_trywrlock(netdata_rwlock_t *rwlock) {
     return ret;
 }
 
+// ----------------------------------------------------------------------------
+// spinlock implementation
+// https://www.youtube.com/watch?v=rmGJc9PXpuE&t=41s
+
+void netdata_spinlock_init(SPINLOCK *spinlock) {
+    *spinlock = NETDATA_SPINLOCK_INITIALIZER;
+}
+
+void netdata_spinlock_lock(SPINLOCK *spinlock) {
+    static const struct timespec ns = { .tv_sec = 0, .tv_nsec = 1 };
+
+    netdata_thread_disable_cancelability();
+
+    for(int i = 1;
+        __atomic_load_n(&spinlock->locked, __ATOMIC_RELAXED) ||
+        __atomic_test_and_set(&spinlock->locked, __ATOMIC_ACQUIRE)
+        ; i++
+        ) {
+        if(unlikely(i == 8)) {
+            i = 0;
+            nanosleep(&ns, NULL);
+        }
+    }
+    // we have the lock
+}
+
+void netdata_spinlock_unlock(SPINLOCK *spinlock) {
+    __atomic_clear(&spinlock->locked, __ATOMIC_RELEASE);
+    netdata_thread_enable_cancelability();
+}
+
 #ifdef NETDATA_TRACE_RWLOCKS
 
 // ----------------------------------------------------------------------------
diff --git a/libnetdata/locks/locks.h b/libnetdata/locks/locks.h
index 796b53c6d..4d2d1655c 100644
--- a/libnetdata/locks/locks.h
+++ b/libnetdata/locks/locks.h
@@ -9,6 +9,14 @@
 typedef pthread_mutex_t netdata_mutex_t;
 #define NETDATA_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
 
+typedef struct netdata_spinlock {
+    bool locked;
+} SPINLOCK;
+#define NETDATA_SPINLOCK_INITIALIZER (SPINLOCK){ .locked = false }
+void netdata_spinlock_init(SPINLOCK *spinlock);
+void netdata_spinlock_lock(SPINLOCK *spinlock);
+void netdata_spinlock_unlock(SPINLOCK *spinlock);
+
 #ifdef NETDATA_TRACE_RWLOCKS
 typedef struct netdata_rwlock_locker {
     pid_t pid;
@@ -51,38 +59,38 @@ typedef struct netdata_rwlock_t {
 
 #endif // NETDATA_TRACE_RWLOCKS
 
-extern int __netdata_mutex_init(netdata_mutex_t *mutex);
-extern int __netdata_mutex_destroy(netdata_mutex_t *mutex);
-extern int __netdata_mutex_lock(netdata_mutex_t *mutex);
-extern int __netdata_mutex_trylock(netdata_mutex_t *mutex);
-extern int __netdata_mutex_unlock(netdata_mutex_t *mutex);
+int __netdata_mutex_init(netdata_mutex_t *mutex);
+int __netdata_mutex_destroy(netdata_mutex_t *mutex);
+int __netdata_mutex_lock(netdata_mutex_t *mutex);
+int __netdata_mutex_trylock(netdata_mutex_t *mutex);
+int __netdata_mutex_unlock(netdata_mutex_t *mutex);
 
-extern int __netdata_rwlock_destroy(netdata_rwlock_t *rwlock);
-extern int __netdata_rwlock_init(netdata_rwlock_t *rwlock);
-extern int __netdata_rwlock_rdlock(netdata_rwlock_t *rwlock);
-extern int __netdata_rwlock_wrlock(netdata_rwlock_t *rwlock);
-extern int __netdata_rwlock_unlock(netdata_rwlock_t *rwlock);
-extern int __netdata_rwlock_tryrdlock(netdata_rwlock_t *rwlock);
-extern int __netdata_rwlock_trywrlock(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_destroy(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_init(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_rdlock(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_wrlock(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_unlock(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_tryrdlock(netdata_rwlock_t *rwlock);
+int __netdata_rwlock_trywrlock(netdata_rwlock_t *rwlock);
 
-extern void netdata_thread_disable_cancelability(void);
-extern void netdata_thread_enable_cancelability(void);
+void netdata_thread_disable_cancelability(void);
+void netdata_thread_enable_cancelability(void);
 
 #ifdef NETDATA_TRACE_RWLOCKS
 
-extern int netdata_mutex_init_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
-extern int netdata_mutex_destroy_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
-extern int netdata_mutex_lock_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
-extern int netdata_mutex_trylock_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
-extern int netdata_mutex_unlock_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
-
-extern int netdata_rwlock_destroy_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
-extern int netdata_rwlock_init_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
-extern int netdata_rwlock_rdlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
-extern int netdata_rwlock_wrlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
-extern int netdata_rwlock_unlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
-extern int netdata_rwlock_tryrdlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
-extern int netdata_rwlock_trywrlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_mutex_init_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
+int netdata_mutex_destroy_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
+int netdata_mutex_lock_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
+int netdata_mutex_trylock_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
+int netdata_mutex_unlock_debug( const char *file, const char *function, const unsigned long line, netdata_mutex_t *mutex);
+
+int netdata_rwlock_destroy_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_rwlock_init_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_rwlock_rdlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_rwlock_wrlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_rwlock_unlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_rwlock_tryrdlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
+int netdata_rwlock_trywrlock_debug( const char *file, const char *function, const unsigned long line, netdata_rwlock_t *rwlock);
 
 #define netdata_mutex_init(mutex)    netdata_mutex_init_debug(__FILE__, __FUNCTION__, __LINE__, mutex)
 #define netdata_mutex_destroy(mutex) netdata_mutex_init_debug(__FILE__, __FUNCTION__, __LINE__, mutex)