[PATCH RT 2/3] rt: PREEMPT_RT safety net for backported patches

From: Clark Williams <[email protected]>

v4.14.320-rt152-rc1 stable review patch.
If anyone has any objections, please let me know.

-----------


[ commit 67821680a2b828aa405a2db5d7dbd812a3684fcf from v4.19-rt ]

While doing some 4.19-rt cleanup work, I stumbled across the fact that parts of
two backported patches were dependent on CONFIG_PREEMPT_RT, rather than
the CONFIG_PREEMPT_RT_FULL used in 4.19 and earlier RT series.  The commits
in the linux-stable-rt v4.19-rt branch are:

dad4c6a33bf4e mm: slub: Don't resize the location tracking cache on PREEMPT_RT
e626b6f873f2c net: Treat __napi_schedule_irqoff() as __napi_schedule() on PREEMPT_RT

Discussing this at the Stable RT maintainers meeting, Steven Rostedt suggested that
we automagically select CONFIG_PREEMPT_RT if CONFIG_PREEMPT_RT_FULL is on, giving
us a safety net for any subsequently backported patches. Here's my first cut at
that patch.

I suspect we'll need a similar patch for stable RT kernels < 4.19.

Suggested-by: Steven Rostedt <[email protected]>
Signed-off-by: Clark Williams <[email protected]>
Signed-off-by: Luis Claudio R. Goncalves <[email protected]>
---
 kernel/Kconfig.preempt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 11dbe26a8279..97875b4eb569 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -6,6 +6,9 @@ config PREEMPT_RT_BASE
 	bool
 	select PREEMPT
 
+config PREEMPT_RT
+       bool
+
 config HAVE_PREEMPT_LAZY
 	bool
 
@@ -78,6 +81,7 @@ config PREEMPT_RT_FULL
 	depends on IRQ_FORCED_THREADING
 	select PREEMPT_RT_BASE
 	select PREEMPT_RCU
+	select PREEMPT_RT
 	help
 	  All and everything
 
-- 
2.41.0