From: Waiman Long longman@redhat.com
[ Upstream commit 6da9f775175e516fc7229ceaa9b54f8f56aa7924 ]
When debugging options are turned on, the rcu_read_lock() function might not be inlined. This results in lockdep's print_lock() function printing "rcu_read_lock+0x0/0x70" instead of rcu_read_lock()'s caller. For example:
[ 10.579995] ============================= [ 10.584033] WARNING: suspicious RCU usage [ 10.588074] 4.18.0.memcg_v2+ #1 Not tainted [ 10.593162] ----------------------------- [ 10.597203] include/linux/rcupdate.h:281 Illegal context switch in RCU read-side critical section! [ 10.606220] [ 10.606220] other info that might help us debug this: [ 10.606220] [ 10.614280] [ 10.614280] rcu_scheduler_active = 2, debug_locks = 1 [ 10.620853] 3 locks held by systemd/1: [ 10.624632] #0: (____ptrval____) (&type->i_mutex_dir_key#5){.+.+}, at: lookup_slow+0x42/0x70 [ 10.633232] #1: (____ptrval____) (rcu_read_lock){....}, at: rcu_read_lock+0x0/0x70 [ 10.640954] #2: (____ptrval____) (rcu_read_lock){....}, at: rcu_read_lock+0x0/0x70
These "rcu_read_lock+0x0/0x70" strings are not providing any useful information. This commit therefore forces inlining of the rcu_read_lock() function so that rcu_read_lock()'s caller is instead shown.
Signed-off-by: Waiman Long longman@redhat.com Signed-off-by: Paul E. McKenney paulmck@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index addd03641e1a..0a93e9d1708e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -852,7 +852,7 @@ static inline void rcu_preempt_sleep_check(void) * read-side critical sections may be preempted and they may also block, but * only when acquiring spinlocks that are subject to priority inheritance. */ -static inline void rcu_read_lock(void) +static __always_inline void rcu_read_lock(void) { __rcu_read_lock(); __acquire(RCU);