thread: Add a function to get the thread from a context

This is the inverse of spdk_thread_get_ctx.

Change-Id: I81541ff1687cfea358cb7046caf69982c38f6a38
Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-on: https://review.gerrithub.io/c/444455
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>

include/spdk/thread.h

@@ -222,6 +222,16 @@ void spdk_thread_exit(struct spdk_thread *thread);
  */
 void *spdk_thread_get_ctx(struct spdk_thread *thread);
 
+/**
+ * Return the thread object associated with the context handle previously
+ * obtained by calling spdk_thread_get_ctx().
+ *
+ * \param ctx A context previously obtained by calling spdk_thread_get_ctx()
+ *
+ * \return The associated thread.
+ */
+struct spdk_thread *spdk_thread_get_from_ctx(void *ctx);
+
 /**
  * Perform one iteration worth of processing on the thread. This includes
  * both expired and continuous pollers as well as messages.

lib/thread/thread.c

@@ -342,6 +342,19 @@ spdk_thread_get_ctx(struct spdk_thread *thread)
 	return NULL;
 }
 
+struct spdk_thread *
+spdk_thread_get_from_ctx(void *ctx)
+{
+	if (ctx == NULL) {
+		assert(false);
+		return NULL;
+	}
+
+	assert(g_ctx_sz > 0);
+
+	return SPDK_CONTAINEROF(ctx, struct spdk_thread, ctx);
+}
+
 static inline uint32_t
 _spdk_msg_queue_run_batch(struct spdk_thread *thread, uint32_t max_msgs)
 {