From 8d023ed201037b0ad9fdded3e95d73deb7fcfe7c Mon Sep 17 00:00:00 2001
From: Nemo D'ACREMONT <ndacremont@enseirb-matmeca.fr>
Date: Tue, 8 Apr 2025 18:59:41 +0200
Subject: [PATCH] opti: change scheduler to prioritize threads locking mutex

---
 src/thread/thread.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/thread/thread.c b/src/thread/thread.c
index 585320b..7349b95 100644
--- a/src/thread/thread.c
+++ b/src/thread/thread.c
@@ -12,15 +12,16 @@
 #define HAS_STATUS(entry, value) ((entry->status) & (value))
 #define SET_STATUS(entry, value) ((entry->status) |= (value))
 #define UNSET_STATUS(entry, value) ((entry->status) &= ~(value))
-#define FINISHED 0x1
+#define FINISHED (1 << 0)
 #define IS_FINISHED(entry) (HAS_STATUS(entry, FINISHED))
-#define ALLOCATED 0x2
+#define ALLOCATED (1 << 1)
 #define WAS_ALLOCATED(entry) (HAS_STATUS(entry, ALLOCATED))
-#define WAITING 0x4
+#define WAITING (1 << 2)
 #define IS_WAITING(entry) (HAS_STATUS(entry, WAITING))
 #define GET_LAST_WAITED_THREAD(entry) (entry->last_waited ? entry->last_waited->last_thread : NULL)
-#define WAITED 0x8
-#define MUTEX_WAITING (char) 0x10
+#define WAITED (1 << 3)
+#define MUTEX_WAITING (1 << 4)
+#define MUTEX_LOCKING (1 << 5)
 #define IS_WAITED(entry) (HAS_STATUS(entry, WAITED))
 #define IS_MUTEX_WAITING(entry) (HAS_STATUS(entry, MUTEX_WAITING))
 
@@ -51,7 +52,7 @@ struct context_entry_t {
     struct last_thread_t *last_waited;
     struct mutex_fifo_entry_t mutex_fifo_entry;
     int valgrind_id;
-    char status;
+    int status;
     char stack[STACK_SIZE];
 };
 
@@ -84,6 +85,11 @@ int thread_yield(void)
         return 0;
     }
 
+    if (HAS_STATUS(running, MUTEX_LOCKING)) {
+        DBG("skip yield : running thread is locking a mutex");
+        return 0;
+    }
+
 #ifdef FIBO_STRAT
     if (!(IS_YIELD(running)) && !IS_FINISHED(running) && !IS_WAITING(running)) {
         SET_STATUS(running, YIELD);
@@ -423,6 +429,7 @@ int thread_mutex_lock(thread_mutex_t* mutex)
         running->mutex_fifo_entry.thread = running;
         thread_yield();
     }
+    SET_STATUS(running, MUTEX_LOCKING);
 
     mutex->dummy = 1;
     return 0;
@@ -440,6 +447,10 @@ int thread_mutex_unlock(thread_mutex_t* mutex)
         TAILQ_INSERT_TAIL(&scheduler_fifo, first->thread, link);
     }
 
-    return mutex->dummy = 0;
+    mutex->dummy = 0;
+    UNSET_STATUS(running, MUTEX_LOCKING);
+    thread_yield();
+
+    return 0;
 }
 #endif