[Minios-devel] [UNIKRAFT PATCH 3/3] 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 | 29 +++++++++++++++++++++++------
 lib/uklock/mutex.c            |  2 ++
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/lib/uklock/include/uk/mutex.h b/lib/uklock/include/uk/mutex.h
index ff852b45..f9a41a93 100644
--- a/lib/uklock/include/uk/mutex.h
+++ b/lib/uklock/include/uk/mutex.h
@@ -55,41 +55,55 @@ extern "C" {
  */
 struct uk_mutex {
        int locked;
+       int depth;
+       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->locked == 0 || m->owner == current);
                irqf = ukplat_lcpu_save_irqf();
-               if (!m->locked)
+               if (m->locked == 0 || m->owner == current)
                        break;
                ukplat_lcpu_restore_irqf(irqf);
        }
        m->locked = 1;
+       m->depth++;
+       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)
+       if (m->locked == 0 || m->owner == current) {
                ret = m->locked = 1;
+               m->depth++;
+               m->owner = current;
+       }
        ukplat_lcpu_restore_irqf(irqf);
        return ret;
 }
@@ -107,8 +121,11 @@ static inline void uk_mutex_unlock(struct uk_mutex *m)
 
        irqf = ukplat_lcpu_save_irqf();
        UK_ASSERT(m->locked);
-       m->locked = 0;
-       uk_waitq_wake_up(&m->wait);
+       if (--m->depth == 0) {
+               m->locked = 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..07faf1e7 100644
--- a/lib/uklock/mutex.c
+++ b/lib/uklock/mutex.c
@@ -3,5 +3,7 @@
 void uk_mutex_init(struct uk_mutex *m)
 {
        m->locked = 0;
+       m->depth = 0;
+       m->owner = NULL;
        uk_waitq_init(&m->wait);
 }
-- 
2.20.1


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