8.2. Threading API

8.2.1. Overview

If Anjay is compiled with thread safety enabled (WITH_THREAD_SAFETY CMake option), it requires some basic threading primitives to be implemented for the thread safety features to work properly.

The same threading primitives are additionally used by the avs_net and avs_log modules regardless of whether thread safety is enabled or not.

The specific requirements are:

• avs_net requires avs_init_once(),

• avs_log and Anjay thread safety require avs_mutex_create(), avs_mutex_cleanup(), avs_mutex_lock(), avs_mutex_unlock(), and avs_init_once().

In addition, avs_sched optionally depends on avs_condvar_create(), avs_condvar_cleanup(), avs_condvar_notify_all() as well as avs_mutex_* APIs. The dependency can be controlled with WITH_SCHEDULER_THREAD_SAFE CMake option. This option normally has the same setting as WITH_THREAD_SAFETY.

There are two independent implementations of the threading API for compatibility with most platforms:

• based on pthreads,

• based on C11 atomic operations.

Note

You may use either of the implementations listed above as a reference for writing your own if necessary.

8.2.2. List of functions to implement

If, for some reason neither of the default implementations is suitable:

• Use WITH_CUSTOM_AVS_THREADING=ON when running CMake on Anjay,

• Provide an implementation of:

  • avs_mutex_create(),

  • avs_mutex_cleanup(),

  • avs_init_once(),

  • avs_mutex_lock(),

  • avs_mutex_unlock().

• And if you use thread-safe scheduler, also provide implementation for:

  • avs_condvar_create(),

  • avs_condvar_cleanup(),

  • avs_condvar_notify_all().

Note

For signatures and detailed description of listed functions, see

• avs_mutex.h

• avs_init_once.h

• avs_condvar.h

Note

If you intend to operate the library in a single-threaded fashion, you may provide no-op stubs (returning success) of all mentioned primitives.