Changeset 000350f8 in mainline

Timestamp:

2008-07-06T16:16:32Z (16 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

2ec725f

Parents:

515a0102

Message:

Fix deadlock in the 'zones' kconsole command.

File:

• kernel/generic/src/mm/frame.c (modified) (2 diffs)

kernel/generic/src/mm/frame.c

@@ -1215 +1215 @@
         ipl_t ipl;
 
-        ipl = interrupts_disable();
-        spinlock_lock(&zones.lock);
-
 #ifdef __32_BITS__      
         printf("#  base address free frames  busy frames\n");
@@ -1228 +1225 @@
 #endif
         
-        for (i = 0; i < zones.count; i++) {
+        /*
+         * Because printing may require allocation of memory, we may not hold
+         * the frame allocator locks when printing zone statistics.  Therefore,
+         * we simply gather the statistics under the protection of the locks and
+         * print the statistics when the locks have been released.
+         *
+         * When someone adds/removes zones while we are printing the statistics,
+         * we may end up with inaccurate output (e.g. a zone being skipped from
+         * the listing).
+         */
+
+        for (i = 0; ; i++) {
+                uintptr_t base;
+                count_t free_count;
+                count_t busy_count;
+
+                ipl = interrupts_disable();
+                spinlock_lock(&zones.lock);
+                
+                if (i >= zones.count) {
+                        spinlock_unlock(&zones.lock);
+                        interrupts_restore(ipl);
+                        break;
+                }
+
                 zone = zones.info[i];
                 spinlock_lock(&zone->lock);
 
+                base = PFN2ADDR(zone->base);
+                free_count = zone->free_count;
+                busy_count = zone->busy_count;
+
+                spinlock_unlock(&zone->lock);
+                
+                spinlock_unlock(&zones.lock);
+                interrupts_restore(ipl);
+
 #ifdef __32_BITS__
-                printf("%-2u   %10p %12" PRIc " %12" PRIc "\n",
-                    i, PFN2ADDR(zone->base), zone->free_count,
-                    zone->busy_count);
+                printf("%-2u   %10p %12" PRIc " %12" PRIc "\n", i, base,
+                    free_count, busy_count);
 #endif
 
 #ifdef __64_BITS__
-                printf("%-2u   %18p %12" PRIc " %12" PRIc "\n", i,
-                    PFN2ADDR(zone->base), zone->free_count, zone->busy_count);
+                printf("%-2u   %18p %12" PRIc " %12" PRIc "\n", i, base,
+                    free_count, busy_count);
 #endif
                 
-                spinlock_unlock(&zone->lock);
-        }
-        
-        spinlock_unlock(&zones.lock);
-        interrupts_restore(ipl);
+        }
 }