common: introduce bthreads, co-operative barebox threads

With the new setjmp/longjmp/initjmp support, we have all the
architecture support in place to have suspendable green
threads in barebox. These are expected to replace pollers and
workqueues. For now we still have a differentiation between
the main and secondary threads. The main thread is allowed
I/O access unconditionally. If it's in a delay loop, a secondary
thread running needs to be wary of not entering the same driver
and doing hardware manipulation. We already have slices as
mechanism to guard against this, but they aren't used as widely
as needed.

Preferably, in the end, threads will automatically yield until
they can claim a resource (i.e. lock a mutex). Until we are there,
take the same care when using bthreads as with pollers.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 9 insertions, 8 deletions

diff --git a/include/slice.h b/include/slice.h
index b2d65b80cd..cf684300a8 100644
--- a/include/slice.h
+++ b/include/slice.h
@@ -1,6 +1,8 @@
 #ifndef __SLICE_H
 #define __SLICE_H
 
+#include <bthread.h>
+
 enum slice_action {
 	SLICE_ACQUIRE = 1,
 	SLICE_RELEASE = -1,
@@ -35,12 +37,11 @@ void command_slice_release(void);
 
 extern int poller_active;
 
-#ifdef CONFIG_POLLER
-#define assert_command_context() ({    \
-	WARN_ONCE(poller_active, "%s called in poller\n", __func__); \
-})
-#else
-#define assert_command_context() do { } while (0)
-#endif
+#define assert_command_context() do { \
+	WARN_ONCE(IS_ENABLED(CONFIG_POLLER) && poller_active, \
+		  "%s called in poller\n", __func__); \
+	WARN_ONCE(IS_ENABLED(CONFIG_BTHREAD) && !bthread_is_main(current), \
+		  "%s called in secondary bthread\n", __func__); \
+} while (0)
 
-#endif /* __SLICE_H */
+#endif