[Minios-devel] [UNIKRAFT PATCH 4/4] lib/uklock: Make mutex recursive

[Costin Lupu <costin.lupu@xxxxxxxxx>]

This patch changes the existing mutex implementation to support multiple locking
by the same thread.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
---
 lib/uklock/include/uk/mutex.h | 36 ++++++++++++++++++++++++-----------
 lib/uklock/mutex.c            |  3 ++-
 2 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/lib/uklock/include/uk/mutex.h b/lib/uklock/include/uk/mutex.h
index ff852b45..986fa6b2 100644
--- a/lib/uklock/include/uk/mutex.h
+++ b/lib/uklock/include/uk/mutex.h
@@ -54,49 +54,61 @@ extern "C" {
  * uses wait queues for threads
  */
 struct uk_mutex {
-       int locked;
+       int lock_count;
+       struct uk_thread *owner;
        struct uk_waitq wait;
 };
 
 #define        UK_MUTEX_INITIALIZER(name)                              \
-       { 0, __WAIT_QUEUE_INITIALIZER((name).wait) }
+       { 0, 0, NULL, __WAIT_QUEUE_INITIALIZER((name).wait) }
 
 void uk_mutex_init(struct uk_mutex *m);
 
 static inline void uk_mutex_lock(struct uk_mutex *m)
 {
+       struct uk_thread *current;
        unsigned long irqf;
 
        UK_ASSERT(m);
 
+       current = uk_thread_current();
+
        for (;;) {
-               uk_waitq_wait_event(&m->wait, m->locked == 0);
+               uk_waitq_wait_event(&m->wait,
+                       m->lock_count == 0 || m->owner == current);
                irqf = ukplat_lcpu_save_irqf();
-               if (!m->locked)
+               if (m->lock_count == 0 || m->owner == current)
                        break;
                ukplat_lcpu_restore_irqf(irqf);
        }
-       m->locked = 1;
+       m->lock_count++;
+       m->owner = current;
        ukplat_lcpu_restore_irqf(irqf);
 }
 
 static inline int uk_mutex_trylock(struct uk_mutex *m)
 {
+       struct uk_thread *current;
        unsigned long irqf;
        int ret = 0;
 
        UK_ASSERT(m);
 
+       current = uk_thread_current();
+
        irqf = ukplat_lcpu_save_irqf();
-       if (!m->locked)
-               ret = m->locked = 1;
+       if (m->lock_count == 0 || m->owner == current) {
+               ret = 1;
+               m->lock_count++;
+               m->owner = current;
+       }
        ukplat_lcpu_restore_irqf(irqf);
        return ret;
 }
 
 static inline int uk_mutex_is_locked(struct uk_mutex *m)
 {
-       return m->locked;
+       return m->lock_count > 0;
 }
 
 static inline void uk_mutex_unlock(struct uk_mutex *m)
@@ -106,9 +118,11 @@ static inline void uk_mutex_unlock(struct uk_mutex *m)
        UK_ASSERT(m);
 
        irqf = ukplat_lcpu_save_irqf();
-       UK_ASSERT(m->locked);
-       m->locked = 0;
-       uk_waitq_wake_up(&m->wait);
+       UK_ASSERT(m->lock_count > 0);
+       if (--m->lock_count == 0) {
+               m->owner = NULL;
+               uk_waitq_wake_up(&m->wait);
+       }
        ukplat_lcpu_restore_irqf(irqf);
 }
 
diff --git a/lib/uklock/mutex.c b/lib/uklock/mutex.c
index 183a01db..5e5ec9a6 100644
--- a/lib/uklock/mutex.c
+++ b/lib/uklock/mutex.c
@@ -2,6 +2,7 @@
 
 void uk_mutex_init(struct uk_mutex *m)
 {
-       m->locked = 0;
+       m->lock_count = 0;
+       m->owner = NULL;
        uk_waitq_init(&m->wait);
 }
-- 
2.20.1


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