From: Pavel Begunkov <asml.silence@gmail.com>
Date: Thu, 21 Oct 2021 14:30:51 +0100
Subject: [PATCH] percpu_ref: percpu_ref_tryget_live() version holding RCU
Git-commit: 3b13c168186c115501ee7d194460ba2f8c825155
Patch-mainline: v5.16-rc1
References: jsc#PED-1183
Add percpu_ref_tryget_live_rcu(), which is a version of
percpu_ref_tryget_live() but the user is responsible for enclosing it in
a RCU read lock section.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lore.kernel.org/r/3066500d7a6eb3e03f10adf98b87fdb3b1c49db8.1634822969.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
include/linux/percpu-refcount.h | 33 +++++++++++++++++++++++----------
1 file changed, 23 insertions(+), 10 deletions(-)
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index ae16a9856305..b31d3f3312ce 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -266,6 +266,28 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
return percpu_ref_tryget_many(ref, 1);
}
+/**
+ * percpu_ref_tryget_live_rcu - same as percpu_ref_tryget_live() but the
+ * caller is responsible for taking RCU.
+ *
+ * This function is safe to call as long as @ref is between init and exit.
+ */
+static inline bool percpu_ref_tryget_live_rcu(struct percpu_ref *ref)
+{
+ unsigned long __percpu *percpu_count;
+ bool ret = false;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ if (likely(__ref_is_percpu(ref, &percpu_count))) {
+ this_cpu_inc(*percpu_count);
+ ret = true;
+ } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) {
+ ret = atomic_long_inc_not_zero(&ref->data->count);
+ }
+ return ret;
+}
+
/**
* percpu_ref_tryget_live - try to increment a live percpu refcount
* @ref: percpu_ref to try-get
@@ -283,20 +305,11 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
*/
static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
{
- unsigned long __percpu *percpu_count;
bool ret = false;
rcu_read_lock();
-
- if (__ref_is_percpu(ref, &percpu_count)) {
- this_cpu_inc(*percpu_count);
- ret = true;
- } else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) {
- ret = atomic_long_inc_not_zero(&ref->data->count);
- }
-
+ ret = percpu_ref_tryget_live_rcu(ref);
rcu_read_unlock();
-
return ret;
}
--
2.35.3