kernel/linux.git/include/linux/rcupdate.h, branch linux-4.20.y

rcu: Provide functions for determining if call_rcu() has been invoked

2018-08-30T23:03:42+00:00

This commit adds rcu_head_init() and rcu_head_after_call_rcu() functions to help RCU users detect when another CPU has passed the specified rcu_head structure and function to call_rcu(). The rcu_head_init() should be invoked before making the structure visible to RCU readers, and then the rcu_head_after_call_rcu() may be invoked from within an RCU read-side critical section on an rcu_head structure that was obtained during a traversal of the data structure in question. The rcu_head_after_call_rcu() function will return true if the rcu_head structure has already been passed (with the specified function) to call_rcu(), otherwise it will return false. If rcu_head_init() has not been invoked on the rcu_head structure or if the rcu_head (AKA callback) has already been invoked, then rcu_head_after_call_rcu() will do WARN_ON_ONCE(). Reported-by: NeilBrown Signed-off-by: Paul E. McKenney [ paulmck: Apply neilb naming feedback. ]

rcu: Remove !PREEMPT code from rcu_note_voluntary_context_switch()

2018-08-30T23:03:36+00:00

Because RCU-tasks exists only in PREEMPT kernels and because RCU-sched no longer exists in PREEMPT kernels, it is no longer necessary for the rcu_note_voluntary_context_switch() macro to do anything for !PREEMPT kernels. This commit therefore removes !PREEMPT-related code from this macro, namely, the rcu_all_qs(). Signed-off-by: Paul E. McKenney

rcu: Clean up flavor-related definitions and comments in rcupdate.h

2018-08-30T23:03:31+00:00

Signed-off-by: Paul E. McKenney

rcu: Consolidate RCU-sched update-side function definitions

2018-08-30T23:03:26+00:00

This commit saves a few lines by consolidating the RCU-sched function definitions at the end of include/linux/rcupdate.h. This consolidation also makes it easier to remove them all when the time comes. Signed-off-by: Paul E. McKenney

rcu: Consolidate RCU-bh update-side function definitions

2018-08-30T23:03:25+00:00

This commit saves a few lines by consolidating the RCU-bh function definitions at the end of include/linux/rcupdate.h. This consolidation also makes it easier to remove them all when the time comes. Signed-off-by: Paul E. McKenney

rcu: Express Tiny RCU updates in terms of RCU rather than RCU-sched

2018-08-30T23:02:46+00:00

This commit renames Tiny RCU functions so that the lowest level of functionality is RCU (e.g., synchronize_rcu()) rather than RCU-sched (e.g., synchronize_sched()). This provides greater naming compatibility with Tree RCU, which will in turn permit more LoC removal once the RCU-sched and RCU-bh update-side API is removed. Signed-off-by: Paul E. McKenney [ paulmck: Fix Tiny call_rcu()'s EXPORT_SYMBOL() in response to a bug report from kbuild test robot. ]

rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds

2018-08-30T23:02:45+00:00

Now that RCU-preempt knows about preemption disabling, its implementation of synchronize_rcu() works for synchronize_sched(), and likewise for the other RCU-sched update-side API members. This commit therefore confines the RCU-sched update-side code to CONFIG_PREEMPT=n builds, and defines RCU-sched's update-side API members in terms of those of RCU-preempt. This means that any given build of the Linux kernel has only one update-side flavor of RCU, namely RCU-preempt for CONFIG_PREEMPT=y builds and RCU-sched for CONFIG_PREEMPT=n builds. This in turn means that kernels built with CONFIG_RCU_NOCB_CPU=y have only one rcuo kthread per CPU. Signed-off-by: Paul E. McKenney Cc: Andi Kleen

rcu: Update comments and help text for no more RCU-bh updaters

2018-08-30T23:02:42+00:00

This commit updates comments and help text to account for the fact that RCU-bh update-side functions are now simple wrappers for their RCU or RCU-sched counterparts. Signed-off-by: Paul E. McKenney

rcu: Define RCU-bh update API in terms of RCU

2018-08-30T23:02:40+00:00

Now that the main RCU API knows about softirq disabling and softirq's quiescent states, the RCU-bh update code can be dispensed with. This commit therefore removes the RCU-bh update-side implementation and defines RCU-bh's update-side API in terms of that of either RCU-preempt or RCU-sched, depending on the setting of the CONFIG_PREEMPT Kconfig option. In kernels built with CONFIG_RCU_NOCB_CPU=y this has the knock-on effect of reducing by one the number of rcuo kthreads per CPU. Signed-off-by: Paul E. McKenney

rcu: Improve RCU-tasks naming and comments

2018-07-12T22:39:15+00:00

The naming and comments associated with some RCU-tasks code make the faulty assumption that context switches due to cond_resched() are voluntary. As several people pointed out, this is not the case. This commit therefore updates function names and comments to better reflect current reality. Reported-by: Byungchul Park Reported-by: Joel Fernandes Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney