Changeset 3d84734 in mainline

Timestamp:

2024-01-20T17:19:52Z (4 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master

Children:

41bfc64

Parents:

efed95a3

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-01-20 17:18:35)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-01-20 17:19:52)

Message:

Make thread→priority weakly atomic to avoid need for locking

Location:

kernel/generic

Files:

• include/proc/thread.h (modified) (1 diff)
• src/proc/scheduler.c (modified) (5 diffs)
• src/proc/thread.c (modified) (1 diff)
• src/sysinfo/stats.c (modified) (1 diff)

kernel/generic/include/proc/thread.h

@@ -155 +155 @@
 
         /** Thread's priority. Implemented as index to CPU->rq */
-        int priority;
+        atomic_int_fast32_t priority;
         /** Thread ID. */
         thread_id_t tid;

kernel/generic/src/proc/scheduler.c

@@ -314 +314 @@
 
         THREAD->state = Running;
-        THREAD->priority = rq_index;  /* Correct rq index */
+        atomic_set_unordered(&THREAD->priority, rq_index);  /* Correct rq index */
 
         /*
@@ -325 +325 @@
         log(LF_OTHER, LVL_DEBUG,
             "cpu%u: tid %" PRIu64 " (priority=%d, ticks=%" PRIu64
-            ", nrdy=%zu)", CPU->id, THREAD->tid, THREAD->priority,
+            ", nrdy=%zu)", CPU->id, THREAD->tid, rq_index,
             THREAD->ticks, atomic_load(&CPU->nrdy));
 #endif
@@ -389 +389 @@
         assert(atomic_get_unordered(&thread->cpu) == CPU);
 
-        int i = (thread->priority < RQ_COUNT - 1) ?
-            ++thread->priority : thread->priority;
+        int prio = atomic_get_unordered(&thread->priority);
+
+        if (prio < RQ_COUNT - 1) {
+                prio++;
+                atomic_set_unordered(&thread->priority, prio);
+        }
 
         thread->state = Ready;
@@ -396 +400 @@
         irq_spinlock_unlock(&thread->lock, false);
 
-        add_to_rq(thread, CPU, i);
+        add_to_rq(thread, CPU, prio);
 }
 
@@ -407 +411 @@
         assert(thread->state == Sleeping || thread->state == Entering);
 
-        thread->priority = 0;
+        atomic_set_unordered(&thread->priority, 0);
         thread->state = Ready;
 

kernel/generic/src/proc/thread.c

@@ -262 +262 @@
         thread->uncounted =
             ((flags & THREAD_FLAG_UNCOUNTED) == THREAD_FLAG_UNCOUNTED);
-        thread->priority = -1;          /* Start in rq[0] */
+        atomic_init(&thread->priority, -1);          /* Start in rq[0] */
         atomic_init(&thread->cpu, NULL);
         thread->stolen = false;

kernel/generic/src/sysinfo/stats.c

@@ -304 +304 @@
         stats_thread->task_id = thread->task->taskid;
         stats_thread->state = thread->state;
-        stats_thread->priority = thread->priority;
+        stats_thread->priority = atomic_get_unordered(&thread->priority);
         stats_thread->ucycles = thread->ucycles;
         stats_thread->kcycles = thread->kcycles;