Warn if lkl_create_syscall_thread seems unproperly used

arch/lkl/include/uapi/asm/host_ops.h

@@ -23,6 +23,7 @@ struct lkl_sem_t;
  * @sem_free - free a host semaphore
  * @sem_up - perform an up operation on the semaphore
  * @sem_down - perform a down operation on the semaphore
+ * @sem_get - return the current value of semahpore. To be used only for sanity checking
  *
  * @mutex_alloc - allocate and initialize a host mutex
  * @mutex_free - free a host mutex
@@ -66,6 +67,7 @@ struct lkl_host_operations {
  void (*sem_free)(struct lkl_sem_t *sem);
  void (*sem_up)(struct lkl_sem_t *sem);
  void (*sem_down)(struct lkl_sem_t *sem);
+ int (*sem_get)(struct lkl_sem_t *sem);
 
  struct lkl_mutex_t *(*mutex_alloc)(void);
  void (*mutex_free)(struct lkl_mutex_t *mutex);

arch/lkl/kernel/syscalls.c

@@ -147,16 +147,31 @@ static int syscall_thread_data_init(struct syscall_thread_data *data,
  return 0;
 }
 
-long lkl_syscall(long no, long *params)
-{
+static struct syscall_thread_data *lkl_syscall_data(void) {
  struct syscall_thread_data *data = NULL;
- struct syscall s;
 
  if (lkl_ops->tls_get)
  data = lkl_ops->tls_get(syscall_thread_data_key);
  if (!data)
  data = &default_syscall_thread_data;
 
+ return data;
+}
+
+static int lkl_syscall_wouldblock(void) {
+ struct syscall_thread_data *data = lkl_syscall_data();
+
+ if(!lkl_ops->sem_get)
+ return 0;
+
+ return !lkl_ops->sem_get(data->mutex);
+}
+
+long lkl_syscall(long no, long *params)
+{
+ struct syscall_thread_data *data = lkl_syscall_data();
+ struct syscall s;
+
  s.no = no;
  s.params = params;
 
@@ -196,6 +211,9 @@ int lkl_create_syscall_thread(void)
  return ret;
  }
 
+ if(lkl_syscall_wouldblock())
+ pr_warn("lkl: Calling lkl_create_syscall_thread will block\n");
+
  params[0] = (long)data;
  ret = lkl_syscall(__NR_create_syscall_thread, params);
  if (ret < 0) {

tools/lkl/lib/posix-host.c

@@ -123,6 +123,17 @@ static void sem_down(struct lkl_sem_t *sem)
 #endif /* _POSIX_SEMAPHORES */
 }
 
+static int sem_get(struct lkl_sem_t *sem) {
+ int v = 0;
+#ifdef _POSIX_SEMAPHORES
+ WARN_UNLESS(sem_getvalue(&sem->sem, &v));
+#else
+ WARN_PTHREAD(pthread_mutex_lock(&sem->lock));
+ v = sem->count;
+ WARN_PTHREAD(pthread_mutex_unlock(&sem->lock));
+#endif /* _POSIX_SEMAPHORES */
+ return v;
+}
 
 static struct lkl_mutex_t *mutex_alloc(void)
 {
@@ -268,6 +279,7 @@ struct lkl_host_operations lkl_host_ops = {
  .sem_free = sem_free,
  .sem_up = sem_up,
  .sem_down = sem_down,
+ .sem_get = sem_get,
  .mutex_alloc = mutex_alloc,
  .mutex_free = mutex_free,
  .mutex_lock = mutex_lock,