On Tue, Apr 29, 2014 at 08:07:24AM -0400, Rik van Riel wrote:
> On 04/28/2014 05:15 PM, Paul E. McKenney wrote:
> > On Mon, Apr 28, 2014 at 01:32:38PM -0700, Randy Dunlap wrote:
> >> On 04/28/14 13:06, Paul E. McKenney wrote:
>
> >>> Please see below for a patch against next-20140428 that makes this build
> >>> for me. This is derived from Rik's patch, my patch, and is consistent with
> >>> Arnd's patch.
> >>>
> >>> Thanx, Paul
> >>
> >> Thnx, works for me. Finally.
> >
> > Good!
> >
> > Rik, how would you like to proceed with this?
>
> I guess this fix should go into -mm?
Andrew dropped the original patch, so a consolidated patch is needed.
I believe that something like the following is what we ended up with.
Does this look right to you?
Thanx, Paul
------------------------------------------------------------------------
sysrq,rcu: suppress RCU stall warnings while sysrq runs
Some sysrq handlers can run for a long time, because they dump a lot
of data onto a serial console. Having RCU stall warnings pop up in
the middle of them only makes the problem worse.
This patch temporarily disables RCU stall warnings while a sysrq
request is handled.
Signed-off-by: Rik van Riel <riel@xxxxxxxxxx>
[ paulmck: Fix build bugs for obscure config options. ]
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Jiri Kosina <jkosina@xxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Cc: Joern Engel <joern@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Madper Xie <cxie@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
index fc67a89..38d5f9a 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>
@@ -511,6 +512,7 @@ void __handle_sysrq(int key, bool check_mask)
int orig_log_level;
int i;
+ rcu_sysrq_start();
rcu_read_lock();
/*
* Raise the apparent loglevel to maximum so that the sysrq header
@@ -554,6 +556,7 @@ void __handle_sysrq(int key, bool check_mask)
console_loglevel = orig_log_level;
}
rcu_read_unlock();
+ rcu_sysrq_end();
}
void handle_sysrq(int key)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 00a7fd6..f3a672c 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -227,6 +227,17 @@ void rcu_idle_enter(void);
void rcu_idle_exit(void);
void rcu_irq_enter(void);
void rcu_irq_exit(void);
+#ifdef CONFIG_RCU_STALL_COMMON
+void rcu_sysrq_start(void);
+void rcu_sysrq_end(void);
+#else /* #ifdef CONFIG_RCU_STALL_COMMON */
+static inline void rcu_sysrq_start(void)
+{
+}
+static inline void rcu_sysrq_end(void)
+{
+}
+#endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */
#ifdef CONFIG_RCU_USER_QS
void rcu_user_enter(void);
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 4c0a9b0..d22309c 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -320,6 +320,18 @@ int rcu_jiffies_till_stall_check(void)
return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
}
+void rcu_sysrq_start(void)
+{
+ if (!rcu_cpu_stall_suppress)
+ rcu_cpu_stall_suppress = 2;
+}
+
+void rcu_sysrq_end(void)
+{
+ if (rcu_cpu_stall_suppress == 2)
+ rcu_cpu_stall_suppress = 0;
+}
+
static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
{
rcu_cpu_stall_suppress = 1;
--
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