Changeset 1c635d6 in mainline for uspace/srv/ns/task.c

Timestamp:

2014-08-26T15:12:12Z (11 years ago)

Author:

Martin Sucha <sucha14@…>

Branches:

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

Children:

613d644

Parents:

df7f5cea

Message:

Do not hold a task's return value after it has disconnected.

Holding the task's return value meant that if nobody waited
for task's result, it polluted NS's memory. This was apparently
done because of a race between spawning a task and waiting for it.

We solve this problem in another way: ns discards the return value
as soon as the task disconnects from it. This typically happens
when the task finishes its execution. In order to avoid the race,
we send the wait request to ns while spawning the task (i.e. when
we talk to the loader), but before we allow the loaded program
to run.

Fixes #132

File:

• uspace/srv/ns/task.c (modified) (6 diffs)

uspace/srv/ns/task.c

@@ -40 +40 @@
 #include <macros.h>
 #include <malloc.h>
+#include <types/task.h>
 #include "task.h"
 #include "ns.h"
 
-
-/* TODO:
- *
- * As there is currently no convention that each task has to be waited
- * for, the NS can leak memory because of the zombie tasks.
- *
- */
 
 /** Task hash table item. */
@@ -195 +189 @@
                 }
                 
-                hash_table_remove(&task_hash_table, &pr->id);
                 list_remove(&pr->link);
                 free(pr);
@@ -204 +197 @@
 void wait_for_task(task_id_t id, ipc_call_t *call, ipc_callid_t callid)
 {
-        sysarg_t retval;
-        task_exit_t texit;
-        bool remove = false;
-        
         ht_link_t *link = hash_table_find(&task_hash_table, &id);
         hashed_task_t *ht = (link != NULL) ?
@@ -218 +207 @@
         }
         
-        if (!ht->finished) {
-                /* Add to pending list */
-                pending_wait_t *pr =
-                    (pending_wait_t *) malloc(sizeof(pending_wait_t));
-                if (!pr) {
-                        retval = ENOMEM;
-                        goto out;
-                }
-                
-                link_initialize(&pr->link);
-                pr->id = id;
-                pr->callid = callid;
-                list_append(&pr->link, &pending_wait);
+        if (ht->finished) {
+                task_exit_t texit = ht->have_rval ? TASK_EXIT_NORMAL :
+                    TASK_EXIT_UNEXPECTED;
+                ipc_answer_2(callid, EOK, texit, ht->retval);
                 return;
         }
         
-        remove = true;
-        retval = EOK;
-        
-out:
-        if (!(callid & IPC_CALLID_NOTIFICATION)) {
-                texit = ht->have_rval ? TASK_EXIT_NORMAL : TASK_EXIT_UNEXPECTED;
-                ipc_answer_2(callid, retval, texit, ht->retval);
-        }
-        if (remove)
-                hash_table_remove_item(&task_hash_table, link);
+        /* Add to pending list */
+        pending_wait_t *pr =
+            (pending_wait_t *) malloc(sizeof(pending_wait_t));
+        if (!pr) {
+                if (!(callid & IPC_CALLID_NOTIFICATION))
+                        ipc_answer_0(callid, ENOMEM);
+                return;
+        }
+        
+        link_initialize(&pr->link);
+        pr->id = id;
+        pr->callid = callid;
+        list_append(&pr->link, &pending_wait);
 }
 
@@ -314 +297 @@
         ht->retval = IPC_GET_ARG1(*call);
         
+        process_pending_wait();
+        
         return EOK;
 }
@@ -336 +321 @@
         ht->finished = true;
         
+        process_pending_wait();
+        hash_table_remove(&task_hash_table, &id);
+        
         return EOK;
 }