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

 /**
  * @file
  * @brief   Udebug hooks and data structure management.
+ *
  * Udebug is an interface that makes userspace debuggers possible.
- *
- * Functions in this file are executed directly in each thread, which
- * may or may not be the subject of debugging. The udebug_stoppable_begin/end()
- * functions are also executed in the clock interrupt handler. To avoid
- * deadlock, functions in this file are protected from the interrupt
- * by locking the recursive lock THREAD->udebug.int_lock (just an atomic
- * variable). This prevents udebug_stoppable_begin/end() from being
- * executed in the interrupt handler (they are skipped).
- *
- * Functions in udebug_ops.c and udebug_ipc.c execute in different threads,
- * so they needn't be protected from the (preemptible) interrupt-initiated
- * code.
  */
 #include <synch/waitq.h>
 #include <debug.h>
 #include <udebug/udebug.h>
 #include <errno.h>
 #include <arch.h>
-static inline void udebug_int_lock(void)
-{
-    atomic_inc(&THREAD->udebug.int_lock);
-}
-static inline void udebug_int_unlock(void)
-{
-    atomic_dec(&THREAD->udebug.int_lock);
-}
 /** Initialize udebug part of task structure.
+ *
  * Called as part of task structure initialization.
  * @param ut    Pointer to the structure to initialize.
 void udebug_thread_initialize(udebug_thread_t *ut)
+{
     mutex_initialize(&ut->lock, MUTEX_PASSIVE);
     waitq_initialize(&ut->go_wq);
-    /*
-     * At the beginning the thread is stoppable, so int_lock be set, too.
-     */
-    atomic_set(&ut->int_lock, 1);
     ut->go_call = NULL;
+    ut->uspace_state = NULL;
-    ut->stop = true;
+    ut->go = false;
     ut->stoppable = true;
     ut->debug_active = false;
     ut->cur_event = 0; /* none */
+}
     call_t *db_call, *go_call;
     ASSERT(THREAD);
     ASSERT(TASK);
-    udebug_int_lock();
     /* Early check for undebugged tasks */
     if (!udebug_thread_precheck()) {
-        udebug_int_unlock();
         return;
+    }
     mutex_lock(&TASK->udebug.lock);
     } else if (TASK->udebug.dt_state == UDEBUG_TS_ACTIVE) {
         /*
          * Active debugging session
          */
-        if (THREAD->udebug.debug_active && THREAD->udebug.stop) {
+        if (THREAD->udebug.debug_active == true &&
+            THREAD->udebug.go == false) {
             /*
              * Thread was requested to stop - answer go call
              */
             /* Make sure nobody takes this call away from us */
  */
 void udebug_stoppable_end(void)
+{
     /* Early check for undebugged tasks */
     if (!udebug_thread_precheck()) {
-        udebug_int_unlock();
         return;
+    }
 restart:
     mutex_lock(&TASK->udebug.lock);
     mutex_lock(&THREAD->udebug.lock);
     if (THREAD->udebug.debug_active &&
-        THREAD->udebug.stop == true) {
+        THREAD->udebug.go == false) {
         TASK->udebug.begin_call = NULL;
         mutex_unlock(&THREAD->udebug.lock);
         mutex_unlock(&TASK->udebug.lock);
         udebug_wait_for_go(&THREAD->udebug.go_wq);
         goto restart;
-        /* must try again - have to lose stoppability atomically */
+        /* Must try again - have to lose stoppability atomically. */
     } else {
         ++TASK->udebug.not_stoppable_count;
         ASSERT(THREAD->udebug.stoppable == true);
         THREAD->udebug.stoppable = false;
         mutex_unlock(&THREAD->udebug.lock);
         mutex_unlock(&TASK->udebug.lock);
+    }
-    udebug_int_unlock();
+}
 /** Upon being scheduled to run, check if the current thread should stop.
+ *
- * This function is called from clock(). Preemption is enabled.
+ * This function is called from clock().
- * interrupts are disabled, but since this is called after
- * being scheduled-in, we can enable them, if we're careful enough
- * not to allow arbitrary recursion or deadlock with the thread context.
  */
 void udebug_before_thread_runs(void)
+{
-    ipl_t ipl;
-    return;
-    ASSERT(!PREEMPTION_DISABLED);
-    /*
-     * Prevent agains re-entering, such as when preempted inside this
-     * function.
-     */
-    if (atomic_get(&THREAD->udebug.int_lock) != 0)
-        return;
-    udebug_int_lock();
-    ipl = interrupts_enable();
-    /* Now we're free to do whatever we need (lock mutexes, sleep, etc.) */
     /* Check if we're supposed to stop */
     udebug_stoppable_begin();
     udebug_stoppable_end();
-    interrupts_restore(ipl);
-    udebug_int_unlock();
+}
 /** Syscall event hook.
+ *
  * Must be called before and after servicing a system call. This generates
     call_t *call;
     udebug_event_t etype;
     etype = end_variant ? UDEBUG_EVENT_SYSCALL_E : UDEBUG_EVENT_SYSCALL_B;
-    udebug_int_lock();
     /* Early check for undebugged tasks */
     if (!udebug_thread_precheck()) {
-        udebug_int_unlock();
         return;
+    }
     mutex_lock(&TASK->udebug.lock);
     mutex_lock(&THREAD->udebug.lock);
-    /* Must only generate events when in debugging session and have go */
+    /* Must only generate events when in debugging session and is go. */
     if (THREAD->udebug.debug_active != true ||
-        THREAD->udebug.stop == true ||
+        THREAD->udebug.go == false ||
         (TASK->udebug.evmask & UDEBUG_EVMASK(etype)) == 0) {
         mutex_unlock(&THREAD->udebug.lock);
         mutex_unlock(&TASK->udebug.lock);
         return;
+    }
     THREAD->udebug.syscall_args[3] = a4;
     THREAD->udebug.syscall_args[4] = a5;
     THREAD->udebug.syscall_args[5] = a6;
     /*
-     * Make sure udebug.stop is true when going to sleep
+     * Make sure udebug.go is false when going to sleep
      * in case we get woken up by DEBUG_END. (At which
      * point it must be back to the initial true value).
      */
-    THREAD->udebug.stop = true;
+    THREAD->udebug.go = false;
     THREAD->udebug.cur_event = etype;
     ipc_answer(&TASK->answerbox, call);
     mutex_unlock(&THREAD->udebug.lock);
     mutex_unlock(&TASK->udebug.lock);
     udebug_wait_for_go(&THREAD->udebug.go_wq);
-    udebug_int_unlock();
+}
-/** Thread-creation event hook.
+/** Thread-creation event hook combined with attaching the thread.
+ *
  * Must be called when a new userspace thread is created in the debugged
+ * task. Generates a THREAD_B event. Also attaches the thread @a t
+ * to the task @a ta.
+ *
+ * This is necessary to avoid a race condition where the BEGIN and THREAD_READ
+ * requests would be handled inbetween attaching the thread and checking it
+ * for being in a debugging session to send the THREAD_B event. We could then
+ * either miss threads or get some threads both in the thread list
- * task. Generates a THREAD_B event.
+ * and get a THREAD_B event for them.
+ *
  * @param t Structure of the thread being created. Not locked, as the
  *      thread is not executing yet.
+ * @param ta    Task to which the thread should be attached.
  */
-void udebug_thread_b_event(struct thread *t)
+void udebug_thread_b_event_attach(struct thread *t, struct task *ta)
+{
     call_t *call;
-    udebug_int_lock();
     mutex_lock(&TASK->udebug.lock);
     mutex_lock(&THREAD->udebug.lock);
+    thread_attach(t, ta);
     LOG("udebug_thread_b_event\n");
     LOG("- check state\n");
     /* Must only generate events when in debugging session */
     if (THREAD->udebug.debug_active != true) {
-        LOG("- debug_active: %s, udebug.stop: %s\n",
+        LOG("- debug_active: %s, udebug.go: %s\n",
             THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
-            THREAD->udebug.stop ? "yes(-)" : "no(+)");
+            THREAD->udebug.go ? "yes(-)" : "no(+)");
         mutex_unlock(&THREAD->udebug.lock);
         mutex_unlock(&TASK->udebug.lock);
         return;
+    }
     IPC_SET_RETVAL(call->data, 0);
     IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_B);
     IPC_SET_ARG2(call->data, (unative_t)t);
     /*
-     * Make sure udebug.stop is true when going to sleep
+     * Make sure udebug.go is false when going to sleep
      * in case we get woken up by DEBUG_END. (At which
      * point it must be back to the initial true value).
      */
-    THREAD->udebug.stop = true;
+    THREAD->udebug.go = false;
     THREAD->udebug.cur_event = UDEBUG_EVENT_THREAD_B;
     ipc_answer(&TASK->answerbox, call);
     mutex_unlock(&THREAD->udebug.lock);
     mutex_unlock(&TASK->udebug.lock);
     LOG("- sleep\n");
     udebug_wait_for_go(&THREAD->udebug.go_wq);
-    udebug_int_unlock();
+}
 /** Thread-termination event hook.
+ *
  * Must be called when the current thread is terminating.
  */
 void udebug_thread_e_event(void)
+{
     call_t *call;
-    udebug_int_lock();
     mutex_lock(&TASK->udebug.lock);
     mutex_lock(&THREAD->udebug.lock);
     LOG("udebug_thread_e_event\n");
     LOG("- check state\n");
-    /* Must only generate events when in debugging session */
+    /* Must only generate events when in debugging session. */
     if (THREAD->udebug.debug_active != true) {
-/*      printf("- debug_active: %s, udebug.stop: %s\n",
+/*      printf("- debug_active: %s, udebug.go: %s\n",
             THREAD->udebug.debug_active ? "yes(+)" : "no(-)",
-            THREAD->udebug.stop ? "yes(-)" : "no(+)");*/
+            THREAD->udebug.go ? "yes(-)" : "no(+)");*/
         mutex_unlock(&THREAD->udebug.lock);
         mutex_unlock(&TASK->udebug.lock);
         return;
+    }
     call = THREAD->udebug.go_call;
     THREAD->udebug.go_call = NULL;
     IPC_SET_RETVAL(call->data, 0);
     IPC_SET_ARG1(call->data, UDEBUG_EVENT_THREAD_E);
-    /* Prevent any further debug activity in thread */
+    /* Prevent any further debug activity in thread. */
     THREAD->udebug.debug_active = false;
     THREAD->udebug.cur_event = 0;       /* none */
-    THREAD->udebug.stop = true; /* set to initial value */
+    THREAD->udebug.go = false;  /* set to initial value */
     ipc_answer(&TASK->answerbox, call);
     mutex_unlock(&THREAD->udebug.lock);
     mutex_unlock(&TASK->udebug.lock);
-    /* Leave int_lock enabled */
+    /*
-    /* This event does not sleep - debugging has finished in this thread */
+     * This event does not sleep - debugging has finished
+     * in this thread.
+     */
+}
 /**
  * Terminate task debugging session.
+ *
     ipl_t ipl;
     LOG("udebug_task_cleanup()\n");
     LOG("task %" PRIu64 "\n", ta->taskid);
-    udebug_int_lock();
     if (ta->udebug.dt_state != UDEBUG_TS_BEGINNING &&
         ta->udebug.dt_state != UDEBUG_TS_ACTIVE) {
         LOG("udebug_task_cleanup(): task not being debugged\n");
         return EINVAL;
+    }
         flags = t->flags;
         spinlock_unlock(&t->lock);
         interrupts_restore(ipl);
-        /* Only process userspace threads */
+        /* Only process userspace threads. */
         if ((flags & THREAD_FLAG_USPACE) != 0) {
-            /* Prevent any further debug activity in thread */
+            /* Prevent any further debug activity in thread. */
             t->udebug.debug_active = false;
             t->udebug.cur_event = 0;    /* none */
-            /* Still has go? */
+            /* Is the thread still go? */
-            if (t->udebug.stop == false) {
+            if (t->udebug.go == true) {
                 /*
                 * Yes, so clear go. As debug_active == false,
                  * this doesn't affect anything.
                  */
-                t->udebug.stop = true;
+                t->udebug.go = false;
                 /* Answer GO call */
                 LOG("answer GO call with EVENT_FINISHED\n");
                 IPC_SET_RETVAL(t->udebug.go_call->data, 0);
                 IPC_SET_ARG1(t->udebug.go_call->data,
+    }
     ta->udebug.dt_state = UDEBUG_TS_INACTIVE;
     ta->udebug.debugger = NULL;
-    udebug_int_unlock();
     return 0;
+}
 /** @}

Subversion Repositories HelenOS

(root)/branches/dynload/kernel/generic/src/udebug/udebug.c – Rev 3474 → 3674