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| author | Zqiang <qiang1.zhang@intel.com> | 2023-01-18 15:30:14 +0800 |
|---|---|---|
| committer | Joel Fernandes (Google) <joel@joelfernandes.org> | 2023-04-05 13:47:44 +0000 |
| commit | 46103fe01b02169150f16d8d6e028217c5a7abe5 (patch) | |
| tree | b83a426a9684d067d47e5be5c8e002ac574fd8a3 /kernel/rcu | |
| parent | 2450b78e0bb1e034eaa2a33dca689282bd8c892a (diff) | |
| download | linux-46103fe01b02169150f16d8d6e028217c5a7abe5.tar.gz | |
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.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8e880c09ab59ed..e80e8f128c57f4 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); |