Re: [PATCH 3/3] rcu: Drive configuration directly from SMP and PREEMPT
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2011-11-21 16:10:04
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On Sat, 2011-11-19 at 13:50 +0100, John Kacur wrote:
From: Paul E. McKenney <redacted> This commit eliminates the possibility of running TREE_PREEMPT_RCU when SMP=n and of running TINY_RCU when PREEMPT=y. People who really want these combinations can hand-edit init/Kconfig, but eliminating them as choices for production systems reduces the amount of testing required. It will also allow cutting out a few #ifdefs. Note that running TREE_RCU and TINY_RCU on single-CPU systems using SMP-built kernels is still supported.
With this patch, I can see the need for the first patch (although there's things broken even for that), but is this really a stable fix? This looks more of an added feature than a bug fix. It's a bug fix if we consider running tree_rcu on UP a bug. Or better stated, will it break anything if we do that? -- Steve
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Signed-off-by: Paul E. McKenney <redacted> commit 8008e129dc90ff4f7a56cb033d6bd042afe3ed52 upstream Cherry-picked for v3.0-rt and fixed-up merge conflicts Note: This makes the depends lines for these options in init/Kconfig for v3.0-rt match those for v3.2-rc2-rt3 Signed-off-by: John Kacur <jkacur@redhat.com> --- init/Kconfig | 6 +++--- 1 files changed, 3 insertions(+), 3 deletions(-)diff --git a/init/Kconfig b/init/Kconfig index 89e40a4..5c1147e 100644 --- a/init/Kconfig +++ b/init/Kconfig@@ -391,7 +391,7 @@ config TREE_RCU config TREE_PREEMPT_RCU bool "Preemptible tree-based hierarchical RCU" - depends on PREEMPT + depends on PREEMPT && SMP help This option selects the RCU implementation that is designed for very large SMP systems with hundreds or@@ -401,7 +401,7 @@ config TREE_PREEMPT_RCU config TINY_RCU bool "UP-only small-memory-footprint RCU" - depends on !SMP && !PREEMPT_RT_FULL + depends on !PREEMPT && !SMP help This option selects the RCU implementation that is designed for UP systems from which real-time response@@ -410,7 +410,7 @@ config TINY_RCU config TINY_PREEMPT_RCU bool "Preemptible UP-only small-memory-footprint RCU" - depends on !SMP && PREEMPT && !PREEMPT_RT_FULL + depends on PREEMPT && !SMP help This option selects the RCU implementation that is designed for real-time UP systems. This option greatly reduces the