Re: 2.5.70 (virgin) hangs running SDET

[Andrew Morton <akpm@digeo.com>]

"Martin J. Bligh" <mbligh@aracnet.com> wrote:
>
> OK, well backing out dcache_lock-vs-tasklist_lock-take-3.patch does
> indeed seem to fix the problem. It's done 5.5 whole cycles now, and
> still going strong.

Well that patch fixed a real bug.  It abviously added or exposed another
one though.  

I continue to wonder if that task_struct is scrogged.  There seem to be no
other processes holding the lock.

Might be interesting to give the below patch a run with memory debug
enabled.

Also spinlock debugging enabled.  It would be nice to run with preempt and
sleep-in-spinlock debugging enabled too, but I think preempt is broken on
NUMA?

(Anton had a patch which just enabled the beancounting which is needed for
might_sleep() effectiveness without turning on preempt, but it needs more
work for ia32)


diff -puN fs/proc/base.c~a fs/proc/base.c
--- 25/fs/proc/base.c~a	Tue Jun 10 12:40:44 2003
+++ 25-akpm/fs/proc/base.c	Tue Jun 10 12:42:01 2003
@@ -1374,6 +1374,11 @@ struct dentry *proc_pid_lookup(struct in
 
 	dentry->d_op = &pid_base_dentry_operations;
 
+	if (task->bite_me != 0) {
+		printk("corrupted task_struct: 0x%x\n", task->bite_me);
+		BUG();
+	}
+
 	spin_lock(&task->proc_lock);
 	task->proc_dentry = dentry;
 	d_add(dentry, inode);
diff -puN include/linux/sched.h~a include/linux/sched.h
--- 25/include/linux/sched.h~a	Tue Jun 10 12:40:44 2003
+++ 25-akpm/include/linux/sched.h	Tue Jun 10 12:40:44 2003
@@ -330,6 +330,8 @@ struct task_struct {
 	struct list_head run_list;
 	prio_array_t *array;
 
+	u32 bite_me;
+
 	unsigned long sleep_avg;
 	unsigned long last_run;
 

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