From 94d24fc47219219b5aa23b45956cc37ee5aa5b01 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Tue, 7 Jun 2011 11:17:30 +0200
Subject: printk, lockdep: Disable lock debugging on zap_locks()

zap_locks() is used by printk() in a last ditch effort to get data
out, clearly we cannot trust lock state after this so make it disable
lock debugging.

Also don't treat printk recursion through lockdep as a normal
recursion bug but try hard to get the lockdep splat out.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-kqxwmo4xz37e1s8w0xopvr0q@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b6a56e3..d36619e 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -343,6 +343,8 @@ extern void lockdep_trace_alloc(gfp_t mask);
 
 #define lockdep_assert_held(l)	WARN_ON(debug_locks && !lockdep_is_held(l))
 
+#define lockdep_recursing(tsk)	((tsk)->lockdep_recursion)
+
 #else /* !LOCKDEP */
 
 static inline void lockdep_off(void)
@@ -392,6 +394,8 @@ struct lock_class_key { };
 
 #define lockdep_assert_held(l)			do { } while (0)
 
+#define lockdep_recursing(tsk)			(0)
+
 #endif /* !LOCKDEP */
 
 #ifdef CONFIG_LOCK_STAT
diff --git a/kernel/printk.c b/kernel/printk.c
index 1455a0d..6d08794 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -688,6 +688,7 @@ static void zap_locks(void)
 
 	oops_timestamp = jiffies;
 
+	debug_locks_off();
 	/* If a crash is occurring, make sure we can't deadlock */
 	raw_spin_lock_init(&logbuf_lock);
 	/* And make sure that we print immediately */
@@ -856,7 +857,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 		 * recursion and return - but flag the recursion so that
 		 * it can be printed at the next appropriate moment:
 		 */
-		if (!oops_in_progress) {
+		if (!oops_in_progress && !lockdep_recursing(current)) {
 			recursion_bug = 1;
 			goto out_restore_irqs;
 		}
-- 
cgit v0.10.2


From 47ff5c95db598184122aa634fa3452c0eecea877 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Tue, 7 Jun 2011 11:17:30 +0200
Subject: printk, lockdep: Remove superfluous preempt_disable()

The raw_lock_irq_{save,restore}() already implies a
non-preemptibility.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/printk.c b/kernel/printk.c
index 6d08794..ba5ee04 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -841,7 +841,6 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	boot_delay_msec();
 	printk_delay();
 
-	preempt_disable();
 	/* This stops the holder of console_sem just where we want him */
 	raw_local_irq_save(flags);
 	this_cpu = smp_processor_id();
@@ -965,7 +964,6 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 out_restore_irqs:
 	raw_local_irq_restore(flags);
 
-	preempt_enable();
 	return printed_len;
 }
 EXPORT_SYMBOL(printk);
-- 
cgit v0.10.2


From 1a9a8aefa8f0530c97f4606ab7a2fc01fe31e9c1 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Tue, 7 Jun 2011 11:17:30 +0200
Subject: printk, lockdep: Switch to tracked irq ops

Switch to local_irq_ ops so that the irq state is properly tracked
(raw_local_irq_* isn't tracked by lockdep, causing confusion).

Possible now that commit dd4e5d3ac4a ("lockdep: Fix
trace_[soft,hard]irqs_[on,off]() recursion") cured the reason we
needed the raw_ ops.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/printk.c b/kernel/printk.c
index ba5ee04..dfd8f73 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -842,7 +842,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	printk_delay();
 
 	/* This stops the holder of console_sem just where we want him */
-	raw_local_irq_save(flags);
+	local_irq_save(flags);
 	this_cpu = smp_processor_id();
 
 	/*
@@ -962,7 +962,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 
 	lockdep_on();
 out_restore_irqs:
-	raw_local_irq_restore(flags);
+	local_irq_restore(flags);
 
 	return printed_len;
 }
-- 
cgit v0.10.2