scheduler: fix idle-thread reentrant bug

moodyhunter · Aug 20, 2024 · 4deb5f7 · 4deb5f7
1 parent ae5be82
commit 4deb5f7
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Showing 7 changed files with 39 additions and 4 deletions.
diff --git a/kernel/arch/x86_64/include/private/mos/platform/platform_defs.h b/kernel/arch/x86_64/include/private/mos/platform/platform_defs.h
@@ -52,6 +52,8 @@
     X(x86_acpi)
 // clang-format on
 
+#define MOS_PLATFORM_MEMORY_BARRIER() __asm__ __volatile__("" ::: "memory")
+
 typedef struct _platform_process_options
 {
     bool iopl;

diff --git a/kernel/include/private/mos/lib/sync/spinlock.h b/kernel/include/private/mos/lib/sync/spinlock.h
@@ -2,9 +2,13 @@
 
 #pragma once
 
+#include "mos/platform/platform_defs.h"
+
 #include <mos/mos_global.h>
 #include <mos/types.h>
 
+#define barrier() MOS_PLATFORM_MEMORY_BARRIER()
+
 typedef struct
 {
     bool flag;
@@ -27,6 +31,7 @@ typedef struct
 #define _spinlock_real_acquire(lock)                                                                                                                                     \
     do                                                                                                                                                                   \
     {                                                                                                                                                                    \
+        barrier();                                                                                                                                                       \
         while (__atomic_test_and_set(&(lock)->flag, __ATOMIC_ACQUIRE))                                                                                                   \
             ;                                                                                                                                                            \
     } while (0)

diff --git a/kernel/include/private/mos/tasks/kthread.h b/kernel/include/private/mos/tasks/kthread.h
@@ -5,4 +5,23 @@
 #include <mos/platform/platform.h>
 
 void kthread_init(void);
+
+/**
+ * @brief Create a kernel-mode thread.
+ *
+ * @param entry The entry point of the thread
+ * @param arg The argument to pass to the thread
+ * @param name The name of the thread
+ * @return thread_t* The created thread
+ */
 thread_t *kthread_create(thread_entry_t entry, void *arg, const char *name);
+
+/**
+ * @brief Create a kernel thread, but do not add it to the scheduler.
+ *
+ * @param entry The entry point of the thread
+ * @param arg The argument to pass to the thread
+ * @param name The name of the thread
+ * @return thread_t* The created thread
+ */
+__nodiscard thread_t *kthread_create_no_sched(thread_entry_t entry, void *arg, const char *name);
diff --git a/kernel/tasks/idle_task.c b/kernel/tasks/idle_task.c
@@ -23,7 +23,7 @@ static void create_idle_task()
         char namebuf[32];
         snprintf(namebuf, sizeof(namebuf), "idle-%u", i);
         pr_dinfo(process, "creating the idle task for CPU %u", i);
-        thread_t *t = kthread_create(idle_task, NULL, namebuf);
+        thread_t *t = kthread_create_no_sched(idle_task, NULL, namebuf);
         platform_info->cpu.percpu_value[i].idle_thread = t;
         // ! scheduler will switch to this thread if no other threads are available, thus scheduler_add_thread isn't called
         // thread_set_cpu(t, i);

diff --git a/kernel/tasks/kthread.c b/kernel/tasks/kthread.c
@@ -34,6 +34,13 @@ void kthread_init(void)
 }
 
 thread_t *kthread_create(thread_entry_t entry, void *arg, const char *name)
+{
+    thread_t *thread = kthread_create_no_sched(entry, arg, name);
+    scheduler_add_thread(thread);
+    return thread;
+}
+
+thread_t *kthread_create_no_sched(thread_entry_t entry, void *arg, const char *name)
 {
     MOS_ASSERT_X(kthreadd, "kthreadd not initialized");
     pr_dinfo2(thread, "creating kernel thread '%s'", name);
@@ -43,6 +50,5 @@ thread_t *kthread_create(thread_entry_t entry, void *arg, const char *name)
     thread_t *thread = thread_new(kthreadd, THREAD_MODE_KERNEL, name, 0, NULL);
     platform_context_setup_child_thread(thread, kthread_entry, kthread_arg);
     thread_complete_init(thread);
-    scheduler_add_thread(thread);
     return thread;
 }
diff --git a/kernel/tasks/schedule.c b/kernel/tasks/schedule.c
@@ -120,7 +120,7 @@ void reschedule(void)
 
     if (!next)
     {
-        if (current->state == THREAD_STATE_RUNNING)
+        if (current && current->state == THREAD_STATE_RUNNING)
         {
             // give the current thread another chance to run, if it's the only one and it's able to run
             MOS_ASSERT_X(spinlock_is_locked(&current->state_lock), "thread state lock must be held");

diff --git a/kernel/tasks/scheduler/naive.c b/kernel/tasks/scheduler/naive.c
@@ -46,7 +46,10 @@ static thread_t *naive_sched_select_next(scheduler_t *instance)
 
     naive_sched_node_t *node = list_entry(scheduler->threads.next, naive_sched_node_t);
     thread_t *thread = node->thread;
-    spinlock_acquire(&thread->state_lock);
+    if (thread == current_thread)
+        spinlock_assert_locked(&thread->state_lock);
+    else
+        spinlock_acquire(&thread->state_lock);
     list_remove(node);
     spinlock_release(&scheduler->lock);