iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

rcu: Force quiescent states only for ongoing grace period

Browse Source 
If an rcutorture test scenario creates an fqs_task kthread, it will
periodically invoke rcu_force_quiescent_state() in order to start
force-quiescent-state (FQS) operations.  However, an FQS operation
will be started even if there is no RCU grace period in progress.
Although testing FQS operations startup when there is no grace period in
progress is necessary, it need not happen all that often.  This commit
therefore causes rcu_force_quiescent_state() to take an early exit
if there is no grace period in progress.

Note that there will still be attempts to start an FQS scan in the
absence of a grace period because the grace period might end right
after the rcu_force_quiescent_state() function's check.  In actual
testing, this happens about once every ten minutes, which should
provide adequate testing.

Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
This commit is contained in:
Zqiang 2023-11-01 11:35:07 +08:00 committed by Neeraj Upadhyay (AMD)
parent 23d90b2404
commit dee39c0c1e
1 changed files with 2 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/rcu/tree.c
View File

@ -2338,6 +2338,8 @@ void rcu_force_quiescent_state(void)
struct rcu_node *rnp;
struct rcu_node *rnp_old = NULL;
if (!rcu_gp_in_progress())
return;
/* Funnel through hierarchy to reduce memory contention. */
rnp = raw_cpu_read(rcu_data.mynode);
for (; rnp != NULL; rnp = rnp->parent) {