Changeset cd671c3 in mainline

Timestamp:

2012-09-05T22:36:48Z (12 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

f1d5ef8

Parents:

239acce

Message:

Reference count call_t structures.
Add ipc_call_hold() and ipc_call_release().
Hold the forgotten call during the request_forget() callback.

Location:

kernel/generic

Files:

• include/ipc/ipc.h (modified) (2 diffs)
• include/ipc/sysipc_ops.h (modified) (1 diff)
• src/ipc/ipc.c (modified) (6 diffs)

kernel/generic/include/ipc/ipc.h

@@ -116 +116 @@
         link_t ta_link;
 
+        atomic_t refcnt;
+
         /** Answerbox link. */
         link_t ab_link;
@@ -166 +168 @@
 extern call_t *ipc_call_alloc(unsigned int);
 extern void ipc_call_free(call_t *);
+extern void ipc_call_hold(call_t *);
+extern void ipc_call_release(call_t *);
 
 extern int ipc_call(phone_t *, call_t *);

kernel/generic/include/ipc/sysipc_ops.h

@@ -55 +55 @@
          * Context:             caller
          * Caller alive:        guaranteed
-         * Races with:          request_process(), answer_cleanup()
+         * Races with:          request_process(), answer_cleanup(),
+         *                      _ipc_answer_free_call()
          * Invoked on:          all forgotten calls
          */     

kernel/generic/src/ipc/ipc.c

@@ -80 +80 @@
 }
 
+void ipc_call_hold(call_t *call)
+{
+        atomic_inc(&call->refcnt);
+}
+
+void ipc_call_release(call_t *call)
+{
+        if (atomic_predec(&call->refcnt) == 0) {
+                if (call->buffer)
+                        free(call->buffer);
+                slab_free(ipc_call_slab, call);
+        }
+}
+
 /** Allocate and initialize a call structure.
  *
@@ -88 +102 @@
  *
  * @return If flags permit it, return NULL, or initialized kernel
- *         call structure.
+ *         call structure with one reference.
  *
  */
@@ -94 +108 @@
 {
         call_t *call = slab_alloc(ipc_call_slab, flags);
-        if (call)
+        if (call) {
                 _ipc_call_init(call);
+                ipc_call_hold(call);
+        }
         
         return call;
@@ -107 +123 @@
 void ipc_call_free(call_t *call)
 {
-        /* Check to see if we have data in the IPC_M_DATA_SEND buffer. */
-        if (call->buffer)
-                free(call->buffer);
-        slab_free(ipc_call_slab, call);
+        ipc_call_release(call);
 }
 
@@ -605 +618 @@
         list_remove(&call->ta_link);
 
+        /*
+         * The call may be freed by _ipc_answer_free_call() before we are done
+         * with it; to avoid working with a destroyed call_t structure, we
+         * must hold a reference to it.
+         */
+        ipc_call_hold(call);
+
         spinlock_unlock(&call->forget_lock);
         spinlock_unlock(&TASK->active_calls_lock);
@@ -613 +633 @@
         if (ops->request_forget)
                 ops->request_forget(call);
+
+        ipc_call_release(call);
 
         goto restart;