[SeaBIOS] [PATCH 3/4] Introduce simple "mutex" locking code.
Kevin O'Connor
kevin at koconnor.net
Wed Mar 10 02:17:27 CET 2010
Locks are not normally necessary because SeaBIOS uses a cooperative
multitasking system. However, occasionally it is necessary to be able
to lock a resource across yield calls. This patch introduces a simple
mechanism for doing that.
---
src/stacks.c | 20 ++++++++++++++++++++
src/util.h | 3 +++
2 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/src/stacks.c b/src/stacks.c
index a35ca3d..c783967 100644
--- a/src/stacks.c
+++ b/src/stacks.c
@@ -248,6 +248,26 @@ wait_threads(void)
yield();
}
+void
+mutex_lock(struct mutex_s *mutex)
+{
+ ASSERT32FLAT();
+ if (! CONFIG_THREADS)
+ return;
+ while (mutex->isLocked)
+ yield();
+ mutex->isLocked = 1;
+}
+
+void
+mutex_unlock(struct mutex_s *mutex)
+{
+ ASSERT32FLAT();
+ if (! CONFIG_THREADS)
+ return;
+ mutex->isLocked = 0;
+}
+
/****************************************************************
* Thread preemption
diff --git a/src/util.h b/src/util.h
index 9f71d65..9b4fd3a 100644
--- a/src/util.h
+++ b/src/util.h
@@ -208,6 +208,9 @@ struct thread_info *getCurThread(void);
void yield(void);
void run_thread(void (*func)(void*), void *data);
void wait_threads(void);
+struct mutex_s { u32 isLocked; };
+void mutex_lock(struct mutex_s *mutex);
+void mutex_unlock(struct mutex_s *mutex);
void start_preempt(void);
void finish_preempt(void);
void check_preempt(void);
--
1.6.6.1
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