Changeset d69f959 in mainline for kernel/generic/src/sysinfo/stats.c

Timestamp:

2010-04-25T19:25:07Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

170332d

Parents:

aa028db

Message:

Take the address space and address space area mutexes conditionally in
get_task_virtmem() so that we never block while holding the tasks and TASK
spinlocks.

File:

• kernel/generic/src/sysinfo/stats.c (modified) (2 diffs)

kernel/generic/src/sysinfo/stats.c

@@ -156 +156 @@
 static size_t get_task_virtmem(as_t *as)
 {
-        mutex_lock(&as->lock);
-        
         size_t result = 0;
+
+        /*
+         * We are holding some spinlocks here and therefore are not allowed to
+         * block. Only attempt to lock the address space and address space area
+         * mutexes conditionally. If it is not possible to lock either object,
+         * allow the statistics to be inexact by skipping the respective object.
+         *
+         * Note that it may be infinitely better to let the address space
+         * management code compute these statistics as it proceeds instead of
+         * having them calculated here over and over again here.
+         */
+
+        if (!mutex_trylock(&as->lock))
+                return result * PAGE_SIZE;
         
         /* Walk the B+ tree and count pages */
@@ -171 +183 @@
                         as_area_t *area = node->value[i];
                         
-                        mutex_lock(&area->lock);
+                        if (!mutex_trylock(&area->lock))
+                                continue;
                         result += area->pages;
                         mutex_unlock(&area->lock);