From b58d977432c80ee60d6970042775a62e3f8d7675 Mon Sep 17 00:00:00 2001
From: Alex Thorlton <athorlton@sgi.com>
Date: Wed, 3 Jul 2013 15:04:59 -0700
Subject: dump_stack: serialize the output from dump_stack()

Add functionality to serialize the output from dump_stack() to avoid
mangling of the output when dump_stack is called simultaneously from
multiple cpus.

[akpm@linux-foundation.org: fix comment indenting, avoid inclusion of <asm/> files - use <linux/> where possiblem fix uniprocessor build (__dump_stack undefined), remove unneeded ifdef around smp.h inclusion]
Signed-off-by: Alex Thorlton <athorlton@sgi.com>
Reported-by: Russ Anderson <rja@sgi.com>
Reviewed-by: Robin Holt <holt@sgi.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 lib/dump_stack.c | 47 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

(limited to 'lib/dump_stack.c')

diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index 53bad099ebd6..c03154173cc7 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -6,15 +6,58 @@
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/atomic.h>
+
+static void __dump_stack(void)
+{
+	dump_stack_print_info(KERN_DEFAULT);
+	show_stack(NULL, NULL);
+}
 
 /**
  * dump_stack - dump the current task information and its stack trace
  *
  * Architectures can override this implementation by implementing its own.
  */
+#ifdef CONFIG_SMP
+static atomic_t dump_lock = ATOMIC_INIT(-1);
+
 void dump_stack(void)
 {
-	dump_stack_print_info(KERN_DEFAULT);
-	show_stack(NULL, NULL);
+	int was_locked;
+	int old;
+	int cpu;
+
+	/*
+	 * Permit this cpu to perform nested stack dumps while serialising
+	 * against other CPUs
+	 */
+	preempt_disable();
+
+retry:
+	cpu = smp_processor_id();
+	old = atomic_cmpxchg(&dump_lock, -1, cpu);
+	if (old == -1) {
+		was_locked = 0;
+	} else if (old == cpu) {
+		was_locked = 1;
+	} else {
+		cpu_relax();
+		goto retry;
+	}
+
+	__dump_stack();
+
+	if (!was_locked)
+		atomic_set(&dump_lock, -1);
+
+	preempt_enable();
+}
+#else
+void dump_stack(void)
+{
+	__dump_stack();
 }
+#endif
 EXPORT_SYMBOL(dump_stack);
-- 
cgit v1.3-8-gc7d7


From b6c035d04e80b4244a143e34e51c84cf2181bd94 Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@linux.intel.com>
Date: Mon, 5 Aug 2013 15:02:48 -0700
Subject: x86, asmlinkage: Make dump_stack visible

dump_stack is used from assembler code, so make it visible.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1375740170-7446-15-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
 include/linux/printk.h | 2 +-
 lib/dump_stack.c       | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

(limited to 'lib/dump_stack.c')

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 22c7052e9372..e6131a782481 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -200,7 +200,7 @@ static inline void show_regs_print_info(const char *log_lvl)
 }
 #endif
 
-extern void dump_stack(void) __cold;
+extern asmlinkage void dump_stack(void) __cold;
 
 #ifndef pr_fmt
 #define pr_fmt(fmt) fmt
diff --git a/lib/dump_stack.c b/lib/dump_stack.c
index c03154173cc7..f23b63f0a1c3 100644
--- a/lib/dump_stack.c
+++ b/lib/dump_stack.c
@@ -23,7 +23,7 @@ static void __dump_stack(void)
 #ifdef CONFIG_SMP
 static atomic_t dump_lock = ATOMIC_INIT(-1);
 
-void dump_stack(void)
+asmlinkage void dump_stack(void)
 {
 	int was_locked;
 	int old;
@@ -55,7 +55,7 @@ retry:
 	preempt_enable();
 }
 #else
-void dump_stack(void)
+asmlinkage void dump_stack(void)
 {
 	__dump_stack();
 }
-- 
cgit v1.3-8-gc7d7