linux-toradex-rt: forward port rt to use latest non rt kernel sources

While at it use consistently the .xz compressed rt-patch file.

Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/recipes-kernel/linux/linux-toradex-rt-4.9-1.0.x/0003-timers-Forward-timer-base-before-migrating-timers.patch b/recipes-kernel/linux/linux-toradex-rt-4.9-1.0.x/0003-timers-Forward-timer-base-before-migrating-timers.patch
new file mode 100644
index 0000000..a6c70d8
--- /dev/null
+++ b/recipes-kernel/linux/linux-toradex-rt-4.9-1.0.x/0003-timers-Forward-timer-base-before-migrating-timers.patch
@@ -0,0 +1,88 @@
+From 030a2d50079f1a8c6319fa6a026c03e43c3f87f6 Mon Sep 17 00:00:00 2001
+From: Lingutla Chandrasekhar <clingutla@codeaurora.org>
+Date: Thu, 18 Jan 2018 17:20:22 +0530
+Subject: [PATCH 3/3] timers: Forward timer base before migrating timers
+
+commit c52232a49e203a65a6e1a670cd5262f59e9364a0 upstream.
+
+On CPU hotunplug the enqueued timers of the unplugged CPU are migrated to a
+live CPU. This happens from the control thread which initiated the unplug.
+
+If the CPU on which the control thread runs came out from a longer idle
+period then the base clock of that CPU might be stale because the control
+thread runs prior to any event which forwards the clock.
+
+In such a case the timers from the unplugged CPU are queued on the live CPU
+based on the stale clock which can cause large delays due to increased
+granularity of the outer timer wheels which are far away from base:;clock.
+
+But there is a worse problem than that. The following sequence of events
+illustrates it:
+
+ - CPU0 timer1 is queued expires = 59969 and base->clk = 59131.
+
+   The timer is queued at wheel level 2, with resulting expiry time = 60032
+   (due to level granularity).
+
+ - CPU1 enters idle @60007, with next timer expiry @60020.
+
+ - CPU0 is hotplugged at @60009
+
+ - CPU1 exits idle and runs the control thread which migrates the
+   timers from CPU0
+
+   timer1 is now queued in level 0 for immediate handling in the next
+   softirq because the requested expiry time 59969 is before CPU1 base->clk
+   60007
+
+ - CPU1 runs code which forwards the base clock which succeeds because the
+   next expiring timer. which was collected at idle entry time is still set
+   to 60020.
+
+   So it forwards beyond 60007 and therefore misses to expire the migrated
+   timer1. That timer gets expired when the wheel wraps around again, which
+   takes between 63 and 630ms depending on the HZ setting.
+
+Address both problems by invoking forward_timer_base() for the control CPUs
+timer base. All other places, which might run into a similar problem
+(mod_timer()/add_timer_on()) already invoke forward_timer_base() to avoid
+that.
+
+[ tglx: Massaged comment and changelog ]
+
+Fixes: a683f390b93f ("timers: Forward the wheel clock whenever possible")
+Co-developed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
+Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
+Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
+Cc: linux-arm-msm@vger.kernel.org
+Cc: stable@vger.kernel.org
+Link: https://lkml.kernel.org/r/20180118115022.6368-1-clingutla@codeaurora.org
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+(cherry picked from commit 13e75c74cd69ca460778fad5ab902f0b20869267)
+---
+ kernel/time/timer.c | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/kernel/time/timer.c b/kernel/time/timer.c
+index ec0169f49c39..00f3db2c6cca 100644
+--- a/kernel/time/timer.c
++++ b/kernel/time/timer.c
+@@ -1919,6 +1919,12 @@ int timers_dead_cpu(unsigned int cpu)
+ 		raw_spin_lock_irq(&new_base->lock);
+ 		raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
+ 
++		/*
++		 * The current CPUs base clock might be stale. Update it
++		 * before moving the timers over.
++		 */
++		forward_timer_base(new_base);
++
+ 		BUG_ON(old_base->running_timer);
+ 
+ 		for (i = 0; i < WHEEL_SIZE; i++)
+-- 
+2.13.6
+