Commit 6da9f775 authored May 21, 2019 by Waiman Long Committed by Paul E. McKenney Jun 13, 2019

rcu: Force inlining of rcu_read_lock()



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>

parent b3119cde

include/linux/rcupdate.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -588,7 +588,7 @@ 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);

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