linux-kernel - Re: adding lockdep support to the Blackfin arch

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Date:	Mon, 8 Jun 2009 19:36:09 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: adding lockdep support to the Blackfin arch

On Mon, Jun 8, 2009 at 19:28, Mike Frysinger wrote:
> ive been extending the Blackfin arch recently to support lockdep.
> since i also had to implement irqflags/stacktrace as well, i wouldnt
> be surprised if this issue is nested in there, plus this is a no-mmu
> system.
>
> at any rate, when i boot up a Blackfin system with PROVE_LOCKING
> enabled, i end up with this warning:
> Badness at kernel/fork.c:988
>
> which correlates to this in copy_process():
>    DEBUG_LOCKS_WARN_ON(!p->hardirqs_enabled);

sorry, stupid stuck keys triggered gmail sending before i finished

when i trace the code, i can see hardirqs_enabled toggling between 0
and 1 ... but when it makes it to copy_process(), apparently it's 0
which annoys the lockdep code.  any tips for me ?

btw, in order to get this to work in the first place, i had to extend
kernel/lockdep.c's static_obj() function as the Blackfin has custom
data regions where some locks live (thus outside of the normal
start/end map).  should this code use kallsyms' helper functions
instead ?  otherwise, i needed this:

--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -634,6 +634,27 @@ static int static_obj(void *obj)
    if ((addr >= start) && (addr < end))
        return 1;

+#ifdef CONFIG_BLACKFIN
+   if (L1_DATA_A_LENGTH) {
+       start = (unsigned long) &_sdata_l1;
+       end   = (unsigned long) &_ebss_l1;
+       if ((addr >= start) && (addr < end))
+           return 1;
+   }
+   if (L1_DATA_B_LENGTH) {
+       start = (unsigned long) &_sdata_b_l1;
+       end   = (unsigned long) &_ebss_b_l1;
+       if ((addr >= start) && (addr < end))
+           return 1;
+   }
+   if (L2_LENGTH) {
+       start = (unsigned long) &_sdata_l2;
+       end   = (unsigned long) &_ebss_l2;
+       if ((addr >= start) && (addr < end))
+           return 1;
+   }
+#endif
+
 #ifdef CONFIG_SMP
    /*
     * percpu var?
-mike
--
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