From 9eeba6138cefc0435695463ddadb0d95e0a6bcd2 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 11 Apr 2009 03:17:17 +0200 Subject: [PATCH 1/2] 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 Cc: Peter Zijlstra LKML-Reference: <1239412638-6739-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- include/linux/debug_locks.h | 7 +++++++ kernel/panic.c | 10 ++++++++-- lib/debug_locks.c | 2 +- 3 files changed, 16 insertions(+), 3 deletions(-) diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h index 096476f1fb35..493dedb7a67b 100644 --- a/include/linux/debug_locks.h +++ b/include/linux/debug_locks.h @@ -2,12 +2,19 @@ #define __LINUX_DEBUG_LOCKING_H #include +#include 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: */ diff --git a/kernel/panic.c b/kernel/panic.c index 3fd8c5bf8b39..940ca14f6dbf 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -213,8 +213,14 @@ unsigned long get_taint(void) void add_taint(unsigned flag) { - /* can't trust the integrity of the kernel anymore: */ - debug_locks = 0; + /* + * Can't trust the integrity of the kernel anymore. + * We don't call directly debug_locks_off() because the issue + * is not necessarily serious enough to set oops_in_progress to 1 + */ + if (__debug_locks_off()) + printk(KERN_WARNING "Disabling lockdep due to kernel taint\n"); + set_bit(flag, &tainted_mask); } EXPORT_SYMBOL(add_taint); diff --git a/lib/debug_locks.c b/lib/debug_locks.c index 0218b4693dd8..bc3b11731b9c 100644 --- a/lib/debug_locks.c +++ b/lib/debug_locks.c @@ -36,7 +36,7 @@ int debug_locks_silent; */ int debug_locks_off(void) { - if (xchg(&debug_locks, 0)) { + if (__debug_locks_off()) { if (!debug_locks_silent) { oops_in_progress = 1; console_verbose(); From 574bbe782057fdf0490dc7dec906a2dc26363e20 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sat, 11 Apr 2009 03:17:18 +0200 Subject: [PATCH 2/2] lockdep: continue lock debugging despite some taints Impact: broaden lockdep checks Lockdep is disabled after any kernel taints. This might be convenient to ignore bad locking issues which sources come from outside the kernel tree. Nevertheless, it might be a frustrating experience for the staging developers or those who experience a warning but are focused on another things that require lockdep. The v2 of this patch simply don't disable anymore lockdep in case of TAINT_CRAP and TAINT_WARN events. Signed-off-by: Frederic Weisbecker Cc: LTP Cc: Peter Zijlstra Cc: Greg KH LKML-Reference: <1239412638-6739-2-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar --- kernel/panic.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/panic.c b/kernel/panic.c index 940ca14f6dbf..934fb377f4b3 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -217,8 +217,10 @@ void add_taint(unsigned flag) * Can't trust the integrity of the kernel anymore. * We don't call directly debug_locks_off() because the issue * is not necessarily serious enough to set oops_in_progress to 1 + * Also we want to keep up lockdep for staging development and + * post-warning case. */ - if (__debug_locks_off()) + if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off()) printk(KERN_WARNING "Disabling lockdep due to kernel taint\n"); set_bit(flag, &tainted_mask);