Subject: Re: mmotm 2014-04-24-13-07 uploaded

From: Rik van Riel <[email-masked]>
Date: Fri, 25 Apr 2014 10:04:59 -0400

On Thu, 24 Apr 2014 15:40:29 -0700
Randy Dunlap <[email-masked]> wrote:

> uml on x86_64 defconfig:
> 
> drivers/built-in.o: In function `__handle_sysrq':
> drivers/tty/sysrq.c:514: undefined reference to `rcu_sysrq_start'
> drivers/tty/sysrq.c:558: undefined reference to `rcu_sysrq_end'

Randy, does the patch below fix it?

Mike, this patch should also address your concerns.

Andrew, this can be a -fix patch for the sysctl-rcu patch,
assuming it fixes things :)

Signed-off-by: Rik van Riel <[email-masked]
---
 drivers/tty/sysrq.c | 1 +
 kernel/rcu/update.c | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index dd53af9..0867433 100644
--- a/drivers/tty/sysrq.c
+++ b/drivers/tty/sysrq.c
@@ -46,6 +46,7 @@
 #include <linux/jiffies.h>
 #include <linux/syscalls.h>
 #include <linux/of.h>
+#include <linux/rcupdate.h>
 
 #include <asm/ptrace.h>
 #include <asm/irq_regs.h>
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 2ac3289..d22309c 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -322,7 +322,8 @@ int rcu_jiffies_till_stall_check(void)
 
 void rcu_sysrq_start(void)
 {
-	rcu_cpu_stall_suppress = 2;
+	if (!rcu_cpu_stall_suppress)
+		rcu_cpu_stall_suppress = 2;
 }
 
 void rcu_sysrq_end(void)