mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-28 11:49:32 +00:00
rcu: Make rcu_init_new_rnp() stop upon already-set bit
Currently, rcu_init_new_rnp() walks up the rcu_node combining tree, setting bits in the ->qsmaskinit fields on the way up. It walks up unconditionally, regardless of the initial state of these bits. This is OK because only the corresponding RCU grace-period kthread ever tests or sets these bits during runtime. However, it is also pointless, and it increases both memory and lock contention (albeit only slightly), so this commit stops the walk as soon as an already-set bit is encountered. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
parent
c50cbe535c
commit
8d672fa6bf
1 changed files with 5 additions and 1 deletions
|
@ -3479,9 +3479,10 @@ EXPORT_SYMBOL_GPL(rcu_barrier_sched);
|
|||
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
|
||||
{
|
||||
long mask;
|
||||
long oldmask;
|
||||
struct rcu_node *rnp = rnp_leaf;
|
||||
|
||||
raw_lockdep_assert_held_rcu_node(rnp);
|
||||
raw_lockdep_assert_held_rcu_node(rnp_leaf);
|
||||
WARN_ON_ONCE(rnp->wait_blkd_tasks);
|
||||
for (;;) {
|
||||
mask = rnp->grpmask;
|
||||
|
@ -3489,8 +3490,11 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
|
|||
if (rnp == NULL)
|
||||
return;
|
||||
raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */
|
||||
oldmask = rnp->qsmaskinit;
|
||||
rnp->qsmaskinit |= mask;
|
||||
raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */
|
||||
if (oldmask)
|
||||
return;
|
||||
}
|
||||
}
|
||||
|
||||
|
|
Loading…
Reference in a new issue