WebSVN – HelenOS – Diff – //branches/tracing/kernel/generic/src/udebug/udebug_ipc.c

 /**
  * Get and lock a phone's callee task.
+ *
  * This will return a pointer to the task to which the phone
  * is connected. It will lock the task, making sure it exists.
+ *
+ * Interrupts must be already disabled.
+ *
  * (TODO: make sure the udebug-cleanup of the task hasn't
  * started yet)
  */
 static task_t *get_lock_callee_task(phone_t *phone)
+{
     answerbox_t *box;
     task_t *ta;
     task_id_t taskid;
-    ipl_t ipl;
-    ipl = interrupts_disable();
     spinlock_lock(&phone->lock);
     if (phone->state != IPC_PHONE_CONNECTED) {
         spinlock_unlock(&phone->lock);
-        interrupts_restore(ipl);
         return NULL;
+    }
     box = phone->callee;
     spinlock_lock(&tasks_lock);
     ta = task_find_by_id(taskid);
     if (ta == NULL) {
         spinlock_unlock(&tasks_lock);
-        interrupts_restore(ipl);
         return NULL;
+    }
     spinlock_lock(&ta->lock);
     spinlock_unlock(&tasks_lock);
-    interrupts_restore(ipl);
     return ta;
+}
 /**
     /* Set debug_active on all of the task's userspace threads */
     for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
         t = list_get_instance(cur, thread_t, th_link);
-        spinlock_lock(&t->lock);
+        spinlock_lock(&t->debug_lock);
         if ((t->flags & THREAD_FLAG_USPACE) != 0)
             t->debug_active = true;
-        spinlock_unlock(&t->lock);
+        spinlock_unlock(&t->debug_lock);
+    }
     spinlock_unlock(&ta->lock);
     interrupts_restore(ipl);
     task_t *ta;
     ipl_t ipl;
     thread_t *t;
     link_t *cur;
+    int flags;
     klog_printf("udebug_rp_end()");
     ipl = interrupts_disable();
     ta = get_lock_callee_task(phone);
     for (cur = ta->th_head.next; cur != &ta->th_head; cur = cur->next) {
         t = list_get_instance(cur, thread_t, th_link);
         spinlock_lock(&t->lock);
+        flags = t->flags;
+        spinlock_lock(&t->debug_lock);
+        spinlock_unlock(&t->lock);
         /* Only process userspace threads */
-        if ((t->flags & THREAD_FLAG_USPACE) != 0) {
+        if ((flags & THREAD_FLAG_USPACE) != 0) {
             /* Prevent any further debug activity in thread */
             t->debug_active = false;
             /* Still has go? */
             if (t->debug_stop == false) {
             } else {
                 /*
                  * Debug_stop is already at initial value.
                  * Yet this means the thread needs waking up.
                  */
+                /*
+                 * t's lock must not be held when calling
+                 * waitq_wakeup.
+                 */
                 waitq_wakeup(&t->go_wq, WAKEUP_FIRST);
+            }
+        }
-        spinlock_unlock(&t->lock);
+        spinlock_unlock(&t->debug_lock);
+    }
     ta->dt_state = UDEBUG_TS_INACTIVE;
     spinlock_unlock(&ta->lock);
 static int udebug_rp_go(call_t *call, phone_t *phone)
+{
     thread_t *t;
     task_t *ta;
     ipl_t ipl;
+    int rc;
     klog_printf("debug_go()");
+    ipl = interrupts_disable();
     ta = get_lock_callee_task(phone);
     spinlock_unlock(&ta->lock);
     // TODO: don't lock ta
     t = (thread_t *) IPC_GET_ARG2(call->data);
-    ipl = interrupts_disable();
     spinlock_lock(&threads_lock);
+    if (!thread_exists(t)) {
+        spinlock_unlock(&threads_lock);
+        interrupts_restore(ipl);
+        return ENOENT;
+    }
+    spinlock_lock(&t->debug_lock);
+    /* Verify that thread t may be operated on */
+    rc = verify_thread(t, ta);
+    if (rc != EOK) {
+        spinlock_unlock(&t->debug_lock);
+        spinlock_unlock(&threads_lock);
+        interrupts_restore(ipl);
+        return rc;
+    }
+    /*
+     * Since t->debug_active == true and t->debug_lock is held,
+     * we can safely release threads_lock and t will continue
+     * to exist (and will stay in debug_active state)
+     */
+    spinlock_unlock(&threads_lock);
     t->debug_go_call = call;
     t->debug_stop = false;
+    /*
+     * Neither t's lock nor threads_lock may be held during wakeup
+     */
     waitq_wakeup(&t->go_wq, WAKEUP_FIRST);
-    spinlock_unlock(&threads_lock);
+    spinlock_unlock(&t->debug_lock);
     interrupts_restore(ipl);
     return 0; /* no backsend */
+}
     ipl_t ipl;
     unative_t buffer[6];
     klog_printf("debug_args_read()");
+    ipl = interrupts_disable();
     ta = get_lock_callee_task(phone);
     klog_printf("task %llu", ta->taskid);
     spinlock_unlock(&ta->lock);
     t = (thread_t *) IPC_GET_ARG2(call->data);
-    ipl = interrupts_disable();
     spinlock_lock(&threads_lock);
+    if (!thread_exists(t)) {
+        spinlock_unlock(&threads_lock);
+        interrupts_restore(ipl);
+        return ENOENT;
+    }
+    spinlock_lock(&t->debug_lock);
-    /* Verify that thread t exists and may be operated on */
+    /* Verify that thread t may be operated on */
     rc = verify_thread(t, ta);
     if (rc != EOK) {
+        spinlock_unlock(&t->debug_lock);
         spinlock_unlock(&threads_lock);
         interrupts_restore(ipl);
         return rc;
+    }
+    /*
+     * We can now safely release threads_lock as debug_active == true
+     * and t->debug_lock is held.
+     */
+    spinlock_unlock(&threads_lock);
     //FIXME: additionally we need to verify that we are inside a syscall
     /* Copy to a local buffer before releasing the lock */
     memcpy(buffer, t->syscall_args, 6 * sizeof(unative_t));
-    spinlock_unlock(&threads_lock);
+    spinlock_unlock(&t->debug_lock);
     interrupts_restore(ipl);
     /* Now copy to userspace */
     uspace_buffer = (void *)IPC_GET_ARG3(call->data);
     ipl = interrupts_disable();
     spinlock_lock(&threads_lock);
     t = (thread_t *) IPC_GET_ARG2(call->data);
+    if (!thread_exists(t)) {
+        spinlock_unlock(&threads_lock);
+        interrupts_restore(ipl);
+        return ENOENT;
+    }
+    spinlock_lock(&t->debug_lock);
-    /* Verify that thread t exists and may be operated on */
+    /* Verify that thread t may be operated on */
     rc = verify_thread(t, ta);
     if (rc != EOK) {
+        spinlock_unlock(&t->debug_lock);
         spinlock_unlock(&threads_lock);
         interrupts_restore(ipl);
         return rc;
+    }
+    /*
+     * We can now safely release threads_lock as debug_active == true
+     * and t->debug_lock is held.
+     */
+    spinlock_unlock(&threads_lock);
     state = t->uspace_state;
     if (state == NULL) {
         spinlock_unlock(&threads_lock);
         interrupts_restore(ipl);
         klog_printf("debug_regs_read() - istate not available");
         return EBUSY;
+    }
     /* Copy to a local buffer so that we can release the lock */
     memcpy(&state_copy, state, sizeof(state_copy));
-    spinlock_unlock(&threads_lock);
+    spinlock_unlock(&t->debug_lock);
     interrupts_restore(ipl);
     uspace_buffer = (void *)IPC_GET_ARG3(call->data);
     to_copy = IPC_GET_ARG4(call->data);
     if (to_copy > sizeof(istate_t)) to_copy = sizeof(istate_t);
     rc = copy_to_uspace(uspace_buffer, &state_copy, to_copy);
     if (rc != 0) {
-        spinlock_unlock(&ta->lock);
         klog_printf("debug_regs_read() - copy failed");
         return rc;
+    }
     IPC_SET_ARG1(call->data, to_copy);
     ipl = interrupts_disable();
     spinlock_lock(&threads_lock);
     t = (thread_t *) IPC_GET_ARG2(call->data);
+    if (!thread_exists(t)) {
+        spinlock_unlock(&threads_lock);
+        interrupts_restore(ipl);
+        return ENOENT;
+    }
+    spinlock_lock(&t->debug_lock);
-    /* Verify that thread t exists and may be operated on */
+    /* Verify that thread t may be operated on */
     rc = verify_thread(t, ta);
     if (rc != EOK) {
+        spinlock_unlock(&t->debug_lock);
         spinlock_unlock(&threads_lock);
         interrupts_restore(ipl);
         return rc;
+    }
     state = t->uspace_state;
     if (state == NULL) {
-        spinlock_unlock(&threads_lock);
+        spinlock_unlock(&t->debug_lock);
         interrupts_restore(ipl);
         klog_printf("debug_regs_write() - istate not available");
         return EBUSY;
+    }
     memcpy(t->uspace_state, &data_copy, sizeof(t->uspace_state));
-    spinlock_unlock(&threads_lock);
+    spinlock_unlock(&t->debug_lock);
     interrupts_restore(ipl);
     /* Set answer values */
     IPC_SET_ARG1(call->data, to_copy);

Subversion Repositories HelenOS

(root)//branches/tracing/kernel/generic/src/udebug/udebug_ipc.c – Rev 2842 → 2848