[DRBD-user] DRBD 0.7-pre8 Kernel 2.4.X oops problem

Lars Ellenberg lars.ellenberg at linbit.com
Tue Jun 29 00:34:44 CEST 2004


as someone else already pointed out:
our definitions for the DEFINE_WAIT marco, as well as the
prepare_to_wait and _finish_wait functions, are the problem here.


DEFINE_WAIT is maped to DECLARE_WAIT, which initializes
w.task_list.{prev,next} == NULL, thus list_empty(&wait->task_list) is
false, and the wait thingy is never added to the list in
prepare_to_wait --- but it is removed later in finish_wait, where the
NULL dereference happens.

in 2.6 this problem does not occur,
since there "list_empty_careful" is used...


anyways, this should help
(untested...  I'm not at my own work place,
and currently I can not even do a test compile ...)

	lge

Index: drbd_receiver.c
===================================================================
RCS file: /var/lib/cvs/drbd/drbd/drbd/drbd_receiver.c,v
retrieving revision 1.97.2.175
diff -u -p -r1.97.2.175 drbd_receiver.c
--- drbd_receiver.c	26 Jun 2004 08:05:40 -0000	1.97.2.175
+++ drbd_receiver.c	28 Jun 2004 22:20:14 -0000
@@ -267,7 +267,10 @@ STATIC void finish_wait(wait_queue_head_
 	spin_unlock_irqrestore(&q->lock, flags);
 }
 
-#define DEFINE_WAIT(name)	DECLARE_WAITQUEUE(name,current)
+#define DEFINE_WAIT(name)	do {	\
+	DECLARE_WAITQUEUE(name,current);\
+	list_init(&name.task_list);	\
+} while (0)
 
 #endif
 

> kernel: Unable to handle kernel NULL pointer dereference at virtual address 00000004
> kernel: df5a81cf
> kernel: *pde = 00000000
> kernel: Oops: 0002 2.4.21-215-default #1 Tue Apr 27 16:17:49 UTC 2004
> kernel: CPU:    0
> kernel: EIP:    0010:[drbd:finish_wait+31/48]    Not tainted
> kernel: EIP:    0010:[<df5a81cf>]    Not tainted
> kernel: EFLAGS: 00000086
> kernel: eax: d4e47f38   ebx: d4e47f30   ecx: 00000000   edx: 00000000
> kernel: esi: 00000086   edi: c6370428   ebp: d4e47f30   esp: d4e47ef4
> kernel: ds: 0018   es: 0018   ss: 0018
> kernel: Process drbd0_receiver (pid: 1751, stackpage=d4e47000)
> kernel: Stack: c6370000 c6370468 df5a832a c6370468 d4e47f30 d4e46000 d4e47f18 00000000
> kernel:        d4e46000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> kernel:        d4e46000 00000000 00000000 00000000 c0000000 df5a8976 c9b46508 00001000
> kernel: Call Trace:
	[drbd:drbd_get_ee+330/464] (76)
	[drbd:drbd_recv+134/448] (24)
	[drbd:read_in_block+19/336] (24)



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