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authorZqiang <qiang1.zhang@intel.com>2023-01-18 10:30:14 +0300
committerJoel Fernandes (Google) <joel@joelfernandes.org>2023-04-05 16:47:44 +0300
commit46103fe01b02169150f16d8d6e028217c5a7abe5 (patch)
treeb83a426a9684d067d47e5be5c8e002ac574fd8a3 /kernel/rcu
parent2450b78e0bb1e034eaa2a33dca689282bd8c892a (diff)
downloadlinux-46103fe01b02169150f16d8d6e028217c5a7abe5.tar.xz
rcu: Remove never-set needwake assignment from rcu_report_qs_rdp()
The rcu_accelerate_cbs() function is invoked by rcu_report_qs_rdp() only if there is a grace period in progress that is still blocked by at least one CPU on this rcu_node structure. This means that rcu_accelerate_cbs() should never return the value true, and thus that this function should never set the needwake variable and in turn never invoke rcu_gp_kthread_wake(). This commit therefore removes the needwake variable and the invocation of rcu_gp_kthread_wake() in favor of a WARN_ON_ONCE() on the call to rcu_accelerate_cbs(). The purpose of this new WARN_ON_ONCE() is to detect situations where the system's opinion differs from ours. Signed-off-by: Zqiang <qiang1.zhang@intel.com> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Diffstat (limited to 'kernel/rcu')
-rw-r--r--kernel/rcu/tree.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8e880c09ab59..e80e8f128c57 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1955,7 +1955,6 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
{
unsigned long flags;
unsigned long mask;
- bool needwake = false;
bool needacc = false;
struct rcu_node *rnp;
@@ -1987,7 +1986,12 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
* NOCB kthreads have their own way to deal with that...
*/
if (!rcu_rdp_is_offloaded(rdp)) {
- needwake = rcu_accelerate_cbs(rnp, rdp);
+ /*
+ * The current GP has not yet ended, so it
+ * should not be possible for rcu_accelerate_cbs()
+ * to return true. So complain, but don't awaken.
+ */
+ WARN_ON_ONCE(rcu_accelerate_cbs(rnp, rdp));
} else if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
/*
* ...but NOCB kthreads may miss or delay callbacks acceleration
@@ -1999,8 +2003,6 @@ rcu_report_qs_rdp(struct rcu_data *rdp)
rcu_disable_urgency_upon_qs(rdp);
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
/* ^^^ Released rnp->lock */
- if (needwake)
- rcu_gp_kthread_wake();
if (needacc) {
rcu_nocb_lock_irqsave(rdp, flags);