1 files changed, 76 insertions, 0 deletions

diff --git a/recipes-kernel/linux/files/patches/sched-nohz-Fix-overflow-error-in-scheduler_tick_max_.patch b/recipes-kernel/linux/files/patches/sched-nohz-Fix-overflow-error-in-scheduler_tick_max_.patch
new file mode 100644
index 0000000..c279422
--- /dev/null
+++ b/recipes-kernel/linux/files/patches/sched-nohz-Fix-overflow-error-in-scheduler_tick_max_.patch
@@ -0,0 +1,76 @@
+From 189a149dfc3ab55282b38d2194a0d7def74d8dfa Mon Sep 17 00:00:00 2001
+From: Kevin Hilman <khilman@linaro.org>
+Date: Wed, 15 Jan 2014 14:51:38 +0100
+Subject: [PATCH] sched/nohz: Fix overflow error in
+ scheduler_tick_max_deferment()
+
+While calculating the scheduler tick max deferment, the delta is
+converted from microseconds to nanoseconds through a multiplication
+against NSEC_PER_USEC.
+
+But this microseconds operand is an unsigned int, thus the result may
+likely overflow. The result is cast to u64 but only once the operation
+is completed, which is too late to avoid overflown result.
+
+This is currently not a problem because the scheduler tick max deferment
+is 1 second. But this may become an issue as we plan to make this
+value tunable.
+
+So lets fix this by casting the usecs value to u64 before multiplying by
+NSECS_PER_USEC.
+
+Also to prevent from this kind of mistake to happen again, move this
+ad-hoc jiffies -> nsecs conversion to a new helper.
+
+Signed-off-by: Kevin Hilman <khilman@linaro.org>
+Cc: Thomas Gleixner <tglx@linutronix.de>
+Cc: Ingo Molnar <mingo@kernel.org>
+Cc: Peter Zijlstra <peterz@infradead.org>
+Cc: Alex Shi <alex.shi@linaro.org>
+Cc: Steven Rostedt <rostedt@goodmis.org>
+Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+Cc: John Stultz <john.stultz@linaro.org>
+Cc: Kevin Hilman <khilman@linaro.org>
+Link: http://lkml.kernel.org/r/1387315388-31676-2-git-send-email-khilman@linaro.org
+[move ad-hoc conversion to jiffies_to_nsecs helper]
+Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
+
+Signed-off-by: Mats Liljegren <mats.liljegren@enea.com>
+---
+ include/linux/jiffies.h | 6 ++++++
+ kernel/sched/core.c     | 2 +-
+ 2 files changed, 7 insertions(+), 1 deletion(-)
+
+diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
+index 8fb8edf..4df91d4 100644
+--- a/include/linux/jiffies.h
++++ b/include/linux/jiffies.h
+@@ -290,6 +290,12 @@ extern unsigned long preset_lpj;
+  */
+ extern unsigned int jiffies_to_msecs(const unsigned long j);
+ extern unsigned int jiffies_to_usecs(const unsigned long j);
++
++static inline u64 jiffies_to_nsecs(const unsigned long j)
++{
++       return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
++}
++
+ extern unsigned long msecs_to_jiffies(const unsigned int m);
+ extern unsigned long usecs_to_jiffies(const unsigned int u);
+ extern unsigned long timespec_to_jiffies(const struct timespec *value);
+diff --git a/kernel/sched/core.c b/kernel/sched/core.c
+index e8b3350..45c2cf1 100644
+--- a/kernel/sched/core.c
++++ b/kernel/sched/core.c
+@@ -2774,7 +2774,7 @@ u64 scheduler_tick_max_deferment(void)
+        if (time_before_eq(next, now))
+                return 0;
+ 
+-       return jiffies_to_usecs(next - now) * NSEC_PER_USEC;
++       return jiffies_to_nsecs(next - now);
+ }
+ #endif
+ 
+-- 
+1.9.1
+