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

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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 <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
This commit is contained in:
Paul E. McKenney
2018-07-02 14:30:37 -07:00
parent 4cf439a200
commit 45975c7d21
7 changed files with 307 additions and 479 deletions
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9
kernel/rcu/tree.h
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@@ -225,9 +225,6 @@ struct rcu_data {
/* 5) _rcu_barrier(), OOM callbacks, and expediting. */
struct rcu_head barrier_head;
#ifdef CONFIG_RCU_FAST_NO_HZ
struct rcu_head oom_head;
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
int exp_dynticks_snap; /* Double-check need for IPI. */
/* 6) Callback offloading. */
@@ -433,8 +430,7 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
/* Forward declarations for rcutree_plugin.h */
static void rcu_bootup_announce(void);
static void rcu_preempt_qs(void);
static void rcu_preempt_note_context_switch(bool preempt);
static void rcu_qs(void);
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
#ifdef CONFIG_HOTPLUG_CPU
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
@@ -444,9 +440,8 @@ static int rcu_print_task_stall(struct rcu_node *rnp);
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_state *rsp,
struct rcu_node *rnp);
static void rcu_preempt_check_callbacks(void);
static void rcu_flavor_check_callbacks(int user);
void call_rcu(struct rcu_head *head, rcu_callback_t func);
static void __init __rcu_init_preempt(void);
static void dump_blkd_tasks(struct rcu_state *rsp, struct rcu_node *rnp,
int ncheck);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);