Changeset 31d8e10 in mainline for kernel/generic/src/proc/task.c

Timestamp:

2007-04-05T16:09:49Z (18 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

547fa39

Parents:

879585a3

Message:

Continue to de-oversynchronize the kernel.

• replace as→refcount with an atomic counter; accesses to this

reference counter are not to be done when the as→lock mutex is held;
this gets us rid of mutex_lock_active();

Remove the possibility of a deadlock between TLB shootdown and asidlock.

• get rid of mutex_lock_active() on as→lock
• when locking the asidlock spinlock, always do it conditionally and with

preemption disabled; in the unsuccessful case, enable interrupts and try again

• there should be no deadlock between TLB shootdown and the as→lock mutexes
• PLEASE REVIEW !!!

Add DEADLOCK_PROBE's to places where we have spinlock_trylock() loops.

File:

• kernel/generic/src/proc/task.c (modified) (3 diffs)

kernel/generic/src/proc/task.c

@@ -42 +42 @@
 #include <mm/as.h>
 #include <mm/slab.h>
+#include <atomic.h>
 #include <synch/spinlock.h>
 #include <synch/waitq.h>
@@ -141 +142 @@
         /*
          * Increment address space reference count.
-         * TODO: Reconsider the locking scheme.
-         */
-        mutex_lock(&as->lock);
-        as->refcount++;
-        mutex_unlock(&as->lock);
+         */
+        atomic_inc(&as->refcount);
 
         spinlock_lock(&tasks_lock);
@@ -167 +165 @@
         btree_destroy(&t->futexes);
 
-        mutex_lock_active(&t->as->lock);
-        if (--t->as->refcount == 0) {
-                mutex_unlock(&t->as->lock);
+        if (atomic_predec(&t->as->refcount) == 0) 
                 as_destroy(t->as);
-                /*
-                 * t->as is destroyed.
-                 */
-        } else
-                mutex_unlock(&t->as->lock);
         
         free(t);