SLUB: support slub_debug on by default

Add a new configuration variable

CONFIG_SLUB_DEBUG_ON

If set then the kernel will be booted by default with slab debugging
switched on. Similar to CONFIG_SLAB_DEBUG. By default slab debugging
is available but must be enabled by specifying "slub_debug" as a
kernel parameter.

Also add support to switch off slab debugging for a kernel that was
built with CONFIG_SLUB_DEBUG_ON. This works by specifying

slub_debug=-

as a kernel parameter.

Dave Jones wanted this feature.
http://marc.info/?l=linux-kernel&m=118072189913045&w=2

[akpm@linux-foundation.org: clean up switch statement]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index fab32a286371..640844024ffd 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -152,6 +152,19 @@ config DEBUG_SLAB_LEAK
         bool "Memory leak debugging"
         depends on DEBUG_SLAB
 
+config SLUB_DEBUG_ON
+        bool "SLUB debugging on by default"
+        depends on SLUB && SLUB_DEBUG
+        default n
+        help
+          Boot with debugging on by default. SLUB boots by default with
+          the runtime debug capabilities switched off. Enabling this is
+          equivalent to specifying the "slub_debug" parameter on boot.
+          There is no support for more fine grained debug control like
+          possible with slub_debug=xxx. SLUB debugging may be switched
+          off in a kernel built with CONFIG_SLUB_DEBUG_ON by specifying
+          "slub_debug=-".
+
 config DEBUG_PREEMPT
         bool "Debug preemptible kernel"
         depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT