srcu: Make early-boot call_srcu() reuse workqueue lists

Allocating a list_head structure that is almost never used, and, when
used, is used only during early boot (rcu_init() and earlier), is a bit
wasteful.  This commit therefore eliminates that list_head in favor of
the one in the work_struct structure.  This is safe because the work_struct
structure cannot be used until after rcu_init() returns.

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Paul E. McKenney 2018-08-14 14:41:49 -07:00
parent 55cda2290b
commit 4e6ea4ef56
4 changed files with 11 additions and 15 deletions

View file

@ -186,7 +186,6 @@ static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static)
mutex_init(&sp->srcu_barrier_mutex);
atomic_set(&sp->srcu_barrier_cpu_cnt, 0);
INIT_DELAYED_WORK(&sp->work, process_srcu);
INIT_LIST_HEAD(&sp->srcu_boot_entry);
if (!is_static)
sp->sda = alloc_percpu(struct srcu_data);
init_srcu_struct_nodes(sp, is_static);
@ -708,8 +707,8 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp,
if (likely(srcu_init_done))
queue_delayed_work(rcu_gp_wq, &sp->work,
srcu_get_delay(sp));
else if (list_empty(&sp->srcu_boot_entry))
list_add(&sp->srcu_boot_entry, &srcu_boot_list);
else if (list_empty(&sp->work.work.entry))
list_add(&sp->work.work.entry, &srcu_boot_list);
}
spin_unlock_irqrestore_rcu_node(sp, flags);
}
@ -1323,10 +1322,10 @@ void __init srcu_init(void)
srcu_init_done = true;
while (!list_empty(&srcu_boot_list)) {
sp = list_first_entry(&srcu_boot_list,
struct srcu_struct, srcu_boot_entry);
sp = list_first_entry(&srcu_boot_list, struct srcu_struct,
work.work.entry);
check_init_srcu_struct(sp);
list_del_init(&sp->srcu_boot_entry);
list_del_init(&sp->work.work.entry);
queue_work(rcu_gp_wq, &sp->work.work);
}
}