Changeset b30846e in mainline

Timestamp:

2016-09-17T16:00:57Z (8 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

d701672

Parents:

5a97302

Message:

Do not allow circular paging dependencies of two or more tasks

The mechanism of achieving this is rather simple in that it only allows
pagee-pager relationship between a numerically higher pagee task ID and
a numerically lower pager task ID.

File:

• kernel/generic/src/ipc/ops/pagein.c (modified) (2 diffs)

kernel/generic/src/ipc/ops/pagein.c

@@ -44 +44 @@
 #include <arch.h>
 
+static int pagein_request_process(call_t *call, answerbox_t *box)
+{
+        /*
+         * Allow only requests from numerically higher task IDs to
+         * numerically lower task IDs to prevent deadlock in
+         * pagein_answer_preprocess() that could happen if two tasks
+         * wanted to be each other's pager.
+         */
+        if (call->sender->taskid <= TASK->taskid)
+                return ENOTSUP;
+        else
+                return EOK;
+}
+
 static int pagein_answer_preprocess(call_t *answer, ipc_data_t *olddata)
 {
@@ -85 +99 @@
         .request_preprocess = null_request_preprocess,
         .request_forget = null_request_forget,
-        .request_process = null_request_process,
+        .request_process = pagein_request_process,
         .answer_cleanup = null_answer_cleanup,
         .answer_preprocess = pagein_answer_preprocess,