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

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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
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10
kernel/rcu/srcutiny.c
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@@ -48,7 +48,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp)
sp->srcu_gp_waiting = false;
sp->srcu_idx = 0;
INIT_WORK(&sp->srcu_work, srcu_drive_gp);
INIT_LIST_HEAD(&sp->srcu_boot_entry);
INIT_LIST_HEAD(&sp->srcu_work.entry);
return 0;
}
@@ -185,8 +185,8 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp,
if (!READ_ONCE(sp->srcu_gp_running)) {
if (likely(srcu_init_done))
schedule_work(&sp->srcu_work);
else if (list_empty(&sp->srcu_boot_entry))
list_add(&sp->srcu_boot_entry, &srcu_boot_list);
else if (list_empty(&sp->srcu_work.entry))
list_add(&sp->srcu_work.entry, &srcu_boot_list);
}
}
EXPORT_SYMBOL_GPL(call_srcu);
@@ -224,8 +224,8 @@ 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);
list_del_init(&sp->srcu_boot_entry);
struct srcu_struct, srcu_work.entry);
list_del_init(&sp->srcu_work.entry);
schedule_work(&sp->srcu_work);
}
}