lockdep: warn about lockdep disabling after kernel taint

Impact: provide useful missing info for developers

Kernel taint can occur in several situations such as warnings,
load of prorietary or staging modules, bad page, etc...

But when such taint happens, a developer might still be working on
the kernel, expecting that lockdep is still enabled. But a taint
disables lockdep without ever warning about it.
Such a kernel behaviour doesn't really help for kernel development.

This patch adds this missing warning.

Since the taint is done most of the time after the main message that
explain the real source issue, it seems safe to warn about it inside
add_taint() so that it appears at last, without hurting the main
information.

v2: Use a generic helper to disable lockdep instead of an
    open coded xchg().

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1239412638-6739-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h
index 096476f1fb3..493dedb7a67 100644
--- a/include/linux/debug_locks.h
+++ b/include/linux/debug_locks.h
@@ -2,12 +2,19 @@
 #define __LINUX_DEBUG_LOCKING_H
 
 #include <linux/kernel.h>
+#include <asm/atomic.h>
 
 struct task_struct;
 
 extern int debug_locks;
 extern int debug_locks_silent;
 
+
+static inline int __debug_locks_off(void)
+{
+	return xchg(&debug_locks, 0);
+}
+
 /*
  * Generic 'turn off all lock debugging' function:
  */