On Tue, 2010-05-04 at 14:57 +0800, Yong Zhang wrote: > From 04395389820e89c0bd4bb57b939ec1882e0bb5da Mon Sep 17 00:00:00 2001 > From: Yong Zhang <yong.zhang@xxxxxxxxxxxxx> > Date: Tue, 4 May 2010 14:16:48 +0800 > Subject: [PATCH] lockdep: Reduce stack_trace usage > > When calling check_prevs_add(), if all validations passed > add_lock_to_list() will add new lock to dependency tree and > alloc stack_trace for each list_entry. But at this time, > we are always on the same stack, so stack_trace for each > list_entry has the same value. This is redundant and eats up > lots of memory which could lead to warning on low > MAX_STACK_TRACE_ENTRIES. > Using one copy of stack_trace instead. Right, this looks like it ought to do as intended. I added the below snipped because I know I'll fail to remember and that 'static' qualifier is fairly easy to miss. Thanks! --- Index: linux-2.6/kernel/lockdep.c =================================================================== --- linux-2.6.orig/kernel/lockdep.c +++ linux-2.6/kernel/lockdep.c @@ -1627,6 +1627,13 @@ check_prev_add(struct task_struct *curr, int ret; struct lock_list this; struct lock_list *uninitialized_var(target_entry); + /* + * Static variable, serialized by the graph_lock(). + * + * We use this static variable to save the stack trace in case + * we call into this function multiple times due to encountering + * trylocks in the held lock stack. + */ static struct stack_trace trace; /* -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
