Re: [PATCH tip/core/rcu 1/2] rcu: Provide RCU CPU stall warnings fortiny RCU

[Josh Triplett]

On Sat, Jan 26, 2013 at 04:23:46PM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paul.mckenney@xxxxxxxxxx>
> 
> Tiny RCU has historically omitted RCU CPU stall warnings in order to
> reduce memory requirements, however, lack of these warnings caused
> Thomas Gleixner some debugging pain recently.  Therefore, this commit
> adds RCU CPU stall warnings to tiny RCU if RCU_TRACE=y.  This keeps
> the memory footprint small, while still enabling CPU stall warnings
> in kernels built to enable them.
> 
> Updated to include Josh Triplett's suggested use of RCU_STALL_COMMON
> config variable to simplify #if expressions.
> 
> Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>

One suggestion below; with that change,
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>

> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -486,6 +486,14 @@ config PREEMPT_RCU
>  	  This option enables preemptible-RCU code that is common between
>  	  the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
>  
> +config RCU_STALL_COMMON
> +	def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
> +	help
> +	  This option enables RCU CPU stall code that is common between
> +	  the TINY and TREE variants of RCU.  The purpose is to allow
> +	  the tiny variants to disable RCU CPU stall warnings, while
> +	  making these warnings mandatory for the tree variants.
> +
[...]
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -970,7 +970,7 @@ config RCU_TORTURE_TEST_RUNNABLE
>  
>  config RCU_CPU_STALL_TIMEOUT
>  	int "RCU CPU stall timeout in seconds"
> -	depends on TREE_RCU || TREE_PREEMPT_RCU
> +	depends on TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE

depends on RCU_STALL_COMMON
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