diff options
| author | Waiman Long <longman@redhat.com> | 2021-08-27 05:21:22 +0300 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2021-09-16 20:24:05 +0300 |
| commit | 925da92ba5cb0c82d07cdd5049a07e40f54e9c44 (patch) | |
| tree | d08eedefce6c6633753798c3ee93fbc02b63b3b9 | |
| parent | f0b2b2df5423fb369ac762c77900bc7765496d58 (diff) | |
| download | linux-925da92ba5cb0c82d07cdd5049a07e40f54e9c44.tar.xz | |
rcu: Avoid unneeded function call in rcu_read_unlock()
Since commit aa40c138cc8f3 ("rcu: Report QS for outermost PREEMPT=n
rcu_read_unlock() for strict GPs") the function rcu_read_unlock_strict()
is invoked by the inlined rcu_read_unlock() function. However,
rcu_read_unlock_strict() is an empty function in production kernels,
which are built with CONFIG_RCU_STRICT_GRACE_PERIOD=n.
There is a mention of rcu_read_unlock_strict() in the BPF verifier,
but this is in a deny-list, meaning that BPF does not care whether
rcu_read_unlock_strict() is ever called.
This commit therefore provides a slight performance improvement
by hoisting the check of CONFIG_RCU_STRICT_GRACE_PERIOD from
rcu_read_unlock_strict() into rcu_read_unlock(), thus avoiding the
pointless call to an empty function.
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| -rw-r--r-- | include/linux/rcupdate.h | 3 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 3 |
2 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 434d12fe2d4f..5e0beb5c5659 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -71,7 +71,8 @@ static inline void __rcu_read_lock(void) static inline void __rcu_read_unlock(void) { preempt_enable(); - rcu_read_unlock_strict(); + if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) + rcu_read_unlock_strict(); } static inline int rcu_preempt_depth(void) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index d070059163d7..1a6fdb03d0a5 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -814,8 +814,7 @@ void rcu_read_unlock_strict(void) { struct rcu_data *rdp; - if (!IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) || - irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) + if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread) return; rdp = this_cpu_ptr(&rcu_data); rcu_report_qs_rdp(rdp); |