linux/kernel/rcutiny_plugin.h, branch v3.12

rcu: Add const annotation to char * for RCU tracepoints and functions

2013-07-29T21:07:49Z

All the RCU tracepoints and functions that reference char pointers do so with just 'char *' even though they do not modify the contents of the string itself. This will cause warnings if a const char * is used in one of these functions. The RCU tracepoints store the pointer to the string to refer back to them when the trace output is displayed. As this can be minutes, hours or even days later, those strings had better be constant. This change also opens the door to allow the RCU tracepoint strings and their addresses to be exported so that userspace tracing tools can translate the contents of the pointers of the RCU tracepoints. Signed-off-by: Steven Rostedt

rcu: Shrink TINY_RCU by reworking CPU-stall ifdefs

2013-06-10T20:45:53Z

TINY_RCU's reset_cpu_stall_ticks() and check_cpu_stalls() functions are defined unconditionally, and are empty functions if CONFIG_RCU_TRACE is disabled (which in turns disables detection of RCU CPU stalls). This commit saves a few lines of source code by defining these functions only if CONFIG_RCU_TRACE=y. Signed-off-by: Paul E. McKenney

rcu: Consolidate rcutiny_plugin.h ifdefs

2013-06-10T20:45:52Z

This commit rearranges code in order to allow ifdefs to be consolidated in kernel/rcutiny_plugin.h, simplifying the code. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Remove check_cpu_stall_preempt()

2013-06-10T20:45:51Z

With the removal of CONFIG_TINY_PREEMPT_RCU, check_cpu_stall_preempt() is now an empty function. This commit therefore eliminates it by inlining it. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Simplify RCU_TINY RCU callback invocation

2013-06-10T20:45:51Z

TINY_PREEMPT_RCU could use a kthread to handle RCU callback invocation, which required an API to abstract kthread vs. softirq invocation. Now that TINY_PREEMPT_RCU is no longer with us, this commit retires this API in favor of direct use of the relevant softirq primitives. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Remove rcu_preempt_process_callbacks()

2013-06-10T20:45:50Z

With the removal of CONFIG_TINY_PREEMPT_RCU, rcu_preempt_process_callbacks() is now an empty function. This commit therefore eliminates it by inlining it. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Remove rcu_preempt_remove_callbacks()

2013-06-10T20:45:50Z

With the removal of CONFIG_TINY_PREEMPT_RCU, rcu_preempt_remove_callbacks() is now an empty function. This commit therefore eliminates it by inlining it. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Remove rcu_preempt_check_callbacks()

2013-06-10T20:45:50Z

With the removal of CONFIG_TINY_PREEMPT_RCU, rcu_preempt_check_callbacks() is now an empty function. This commit therefore eliminates it by inlining it. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Remove show_tiny_preempt_stats()

2013-06-10T20:45:49Z

With the removal of CONFIG_TINY_PREEMPT_RCU, show_tiny_preempt_stats() is now an empty function. This commit therefore eliminates it by inlining it. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett

rcu: Remove TINY_PREEMPT_RCU

2013-06-10T20:45:49Z

TINY_PREEMPT_RCU adds significant code and complexity, but does not offer commensurate benefits. People currently using TINY_PREEMPT_RCU can get much better memory footprint with TINY_RCU, or, if they really need preemptible RCU, they can use TREE_PREEMPT_RCU with a relatively minor degradation in memory footprint. Please note that this move has been widely publicized on LKML (https://lkml.org/lkml/2012/11/12/545) and on LWN (http://lwn.net/Articles/541037/). This commit therefore removes TINY_PREEMPT_RCU. Signed-off-by: Paul E. McKenney [ paulmck: Updated to eliminate #else in rcutiny.h as suggested by Josh ] Reviewed-by: Josh Triplett