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Fixed rare threading problem 

From-SVN: r69181
This commit is contained in:
Nicola Pero 2003-07-10 11:24:51 +02:00 committed by Nicola Pero
parent 633221dbab
commit c19f8e352e
2 changed files with 67 additions and 14 deletions
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9
libobjc/ChangeLog
View File

@ -1,3 +1,12 @@
Thu Jul 10 10:27:43 2003 Nicola Pero <n.pero@mi.flashnet.it>
libobjc/9969
* sendmsg.c (get_imp): Fixed rare threading problem.
(__objc_responds_to): Similar fixes.
(objc_msg_lookup): Similar fixes.
(__objc_init_install_dtable): Lock the runtime before checking if the
table is installed.
2003-05-23 Nathanael Nerode <neroden@gcc.gnu.org>
* hash.c, init.c, libobjc.def, libobjc_entry.c, linking.m,

72
libobjc/sendmsg.c
View File

@ -119,6 +119,14 @@ __inline__
IMP
get_imp (Class class, SEL sel)
{
/* In a vanilla implementation we would first check if the dispatch
table is installed. Here instead, to get more speed in the
standard case (that the dispatch table is installed) we first try
to get the imp using brute force. Only if that fails, we do what
we should have been doing from the very beginning, that is, check
if the dispatch table needs to be installed, install it if it's
not installed, and retrieve the imp from the table if it's
installed. */
void *res = sarray_get_safe (class->dtable, (size_t) sel->sel_id);
if (res == 0)
{
@ -127,7 +135,16 @@ get_imp (Class class, SEL sel)
{
/* The dispatch table needs to be installed. */
objc_mutex_lock (__objc_runtime_mutex);
__objc_install_dispatch_table_for_class (class);
/* Double-checked locking pattern: Check
__objc_uninstalled_dtable again in case another thread
installed the dtable while we were waiting for the lock
to be released. */
if (class->dtable == __objc_uninstalled_dtable)
{
__objc_install_dispatch_table_for_class (class);
}
objc_mutex_unlock (__objc_runtime_mutex);
/* Call ourselves with the installed dispatch table
and get the real method */
@ -135,10 +152,22 @@ get_imp (Class class, SEL sel)
}
else
{
/* The dispatch table has been installed so the
method just doesn't exist for the class.
Return the forwarding implementation. */
res = __objc_get_forward_imp (sel);
/* The dispatch table has been installed. */
/* Get the method from the dispatch table (we try to get it
again in case another thread has installed the dtable just
after we invoked sarray_get_safe, but before we checked
class->dtable == __objc_uninstalled_dtable).
*/
res = sarray_get_safe (class->dtable, (size_t) sel->sel_id);
if (res == 0)
{
/* The dispatch table has been installed, and the method
is not in the dispatch table. So the method just
doesn't exist for the class. Return the forwarding
implementation. */
res = __objc_get_forward_imp (sel);
}
}
}
return res;
@ -157,7 +186,10 @@ __objc_responds_to (id object, SEL sel)
if (object->class_pointer->dtable == __objc_uninstalled_dtable)
{
objc_mutex_lock (__objc_runtime_mutex);
__objc_install_dispatch_table_for_class (object->class_pointer);
if (object->class_pointer->dtable == __objc_uninstalled_dtable)
{
__objc_install_dispatch_table_for_class (object->class_pointer);
}
objc_mutex_unlock (__objc_runtime_mutex);
}
@ -192,10 +224,19 @@ objc_msg_lookup (id receiver, SEL op)
}
else
{
/* The dispatch table has been installed so the
method just doesn't exist for the class.
Attempt to forward the method. */
result = __objc_get_forward_imp (op);
/* The dispatch table has been installed. Check again
if the method exists (just in case the dispatch table
has been installed by another thread after we did the
previous check that the method exists).
*/
result = sarray_get_safe (receiver->class_pointer->dtable,
(sidx)op->sel_id);
if (result == 0)
{
/* If the method still just doesn't exist for the
class, attempt to forward the method. */
result = __objc_get_forward_imp (op);
}
}
}
return result;
@ -239,13 +280,16 @@ __objc_init_dispatch_tables ()
static void
__objc_init_install_dtable (id receiver, SEL op __attribute__ ((__unused__)))
{
objc_mutex_lock (__objc_runtime_mutex);
/* This may happen, if the programmer has taken the address of a
method before the dtable was initialized... too bad for him! */
if (receiver->class_pointer->dtable != __objc_uninstalled_dtable)
return;
objc_mutex_lock (__objc_runtime_mutex);
{
objc_mutex_unlock (__objc_runtime_mutex);
return;
}
if (CLS_ISCLASS (receiver->class_pointer))
{
/* receiver is an ordinary object */