diff options
Diffstat (limited to 'debian/patches-rt/percpu-refcount-use-normal-instead-of-RCU-sched.patch')
-rw-r--r-- | debian/patches-rt/percpu-refcount-use-normal-instead-of-RCU-sched.patch | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/debian/patches-rt/percpu-refcount-use-normal-instead-of-RCU-sched.patch b/debian/patches-rt/percpu-refcount-use-normal-instead-of-RCU-sched.patch new file mode 100644 index 000000000..0ee0b78d8 --- /dev/null +++ b/debian/patches-rt/percpu-refcount-use-normal-instead-of-RCU-sched.patch @@ -0,0 +1,101 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Wed, 4 Sep 2019 17:59:36 +0200 +Subject: [PATCH] percpu-refcount: use normal instead of RCU-sched" +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.4/older/patches-5.4.3-rt1.tar.xz + +This is a revert of commit + a4244454df129 ("percpu-refcount: use RCU-sched insted of normal RCU") + +which claims the only reason for using RCU-sched is + "rcu_read_[un]lock() … are slightly more expensive than preempt_disable/enable()" + +and + "As the RCU critical sections are extremely short, using sched-RCU + shouldn't have any latency implications." + +The problem with RCU-sched is that it disables preemption and the +callback must not acquire any sleeping locks like spinlock_t on +PREEMPT_RT which is the case. + +Convert back to normal RCU. + +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + include/linux/percpu-refcount.h | 16 ++++++++-------- + 1 file changed, 8 insertions(+), 8 deletions(-) + +--- a/include/linux/percpu-refcount.h ++++ b/include/linux/percpu-refcount.h +@@ -186,14 +186,14 @@ static inline void percpu_ref_get_many(s + { + unsigned long __percpu *percpu_count; + +- rcu_read_lock_sched(); ++ rcu_read_lock(); + + if (__ref_is_percpu(ref, &percpu_count)) + this_cpu_add(*percpu_count, nr); + else + atomic_long_add(nr, &ref->count); + +- rcu_read_unlock_sched(); ++ rcu_read_unlock(); + } + + /** +@@ -223,7 +223,7 @@ static inline bool percpu_ref_tryget(str + unsigned long __percpu *percpu_count; + bool ret; + +- rcu_read_lock_sched(); ++ rcu_read_lock(); + + if (__ref_is_percpu(ref, &percpu_count)) { + this_cpu_inc(*percpu_count); +@@ -232,7 +232,7 @@ static inline bool percpu_ref_tryget(str + ret = atomic_long_inc_not_zero(&ref->count); + } + +- rcu_read_unlock_sched(); ++ rcu_read_unlock(); + + return ret; + } +@@ -257,7 +257,7 @@ static inline bool percpu_ref_tryget_liv + unsigned long __percpu *percpu_count; + bool ret = false; + +- rcu_read_lock_sched(); ++ rcu_read_lock(); + + if (__ref_is_percpu(ref, &percpu_count)) { + this_cpu_inc(*percpu_count); +@@ -266,7 +266,7 @@ static inline bool percpu_ref_tryget_liv + ret = atomic_long_inc_not_zero(&ref->count); + } + +- rcu_read_unlock_sched(); ++ rcu_read_unlock(); + + return ret; + } +@@ -285,14 +285,14 @@ static inline void percpu_ref_put_many(s + { + unsigned long __percpu *percpu_count; + +- rcu_read_lock_sched(); ++ rcu_read_lock(); + + if (__ref_is_percpu(ref, &percpu_count)) + this_cpu_sub(*percpu_count, nr); + else if (unlikely(atomic_long_sub_and_test(nr, &ref->count))) + ref->release(ref); + +- rcu_read_unlock_sched(); ++ rcu_read_unlock(); + } + + /** |