linux-kernel - [rcu:dev.2019.09.23a 62/77] kernel/rcu/tree.c:2882 kfree_call_rcu() warn: inconsistent returns 'irqsave:flags'.

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Date:   Tue, 24 Sep 2019 11:05:10 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...org, "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     kbuild-all@...org, linux-kernel@...r.kernel.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [rcu:dev.2019.09.23a 62/77] kernel/rcu/tree.c:2882 kfree_call_rcu()
 warn: inconsistent returns 'irqsave:flags'.

tree:   https://kernel.googlesource.com/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2019.09.23a
head:   97de53b94582c208ee239178b208b8e8b9472585
commit: 39676bb72323718a9e7bab1ba9c4a68319a96f62 [62/77] rcu: Add support for debug_objects debugging for kfree_rcu()

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
kernel/rcu/tree.c:2882 kfree_call_rcu() warn: inconsistent returns 'irqsave:flags'.
  Locked on:   line 2867
  Unlocked on: line 2882

git remote add rcu https://kernel.googlesource.com/pub/scm/linux/kernel/git/paulmck/linux-rcu.git
git remote update rcu
git checkout 39676bb72323718a9e7bab1ba9c4a68319a96f62
vim +2882 kernel/rcu/tree.c

5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2850) void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2851) {
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2852) 	unsigned long flags;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2853) 	struct kfree_rcu_cpu *krcp;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2854) 
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2855) 	head->func = func;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2856) 
87970ccf5a9125 Paul E. McKenney        2019-09-19  2857  	local_irq_save(flags);	// For safely calling this_cpu_ptr().
                                                                ^^^^^^^^^^^^^^^^^^^^^
IRQs disabled.

5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2858) 	krcp = this_cpu_ptr(&krc);
ff8db005e371cb Paul E. McKenney        2019-09-19  2859  	if (krcp->initialized)
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2860) 		spin_lock(&krcp->lock);
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2861) 
87970ccf5a9125 Paul E. McKenney        2019-09-19  2862  	// Queue the object but don't yet schedule the batch.
39676bb7232371 Joel Fernandes (Google  2019-09-22  2863) 	if (debug_rcu_head_queue(head)) {
39676bb7232371 Joel Fernandes (Google  2019-09-22  2864) 		// Probable double kfree_rcu(), just leak.
39676bb7232371 Joel Fernandes (Google  2019-09-22  2865) 		WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
39676bb7232371 Joel Fernandes (Google  2019-09-22  2866) 			  __func__, head);
39676bb7232371 Joel Fernandes (Google  2019-09-22  2867) 		return;

Need to re-enable before returning.

39676bb7232371 Joel Fernandes (Google  2019-09-22  2868) 	}
87970ccf5a9125 Paul E. McKenney        2019-09-19  2869  	head->func = func;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2870) 	head->next = krcp->head;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2871) 	krcp->head = head;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2872) 
87970ccf5a9125 Paul E. McKenney        2019-09-19  2873  	// Set timer to drain after KFREE_DRAIN_JIFFIES.
ff8db005e371cb Paul E. McKenney        2019-09-19  2874  	if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
be39848334e088 Paul E. McKenney        2019-09-22  2875  	    !krcp->monitor_todo) {
be39848334e088 Paul E. McKenney        2019-09-22  2876  		krcp->monitor_todo = true;
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2877) 		schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
be39848334e088 Paul E. McKenney        2019-09-22  2878  	}
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2879) 
ff8db005e371cb Paul E. McKenney        2019-09-19  2880  	if (krcp->initialized)
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2881) 		spin_unlock(&krcp->lock);
5f5046cc15d514 Joel Fernandes (Google  2019-08-05 @2882) 	local_irq_restore(flags);
5f5046cc15d514 Joel Fernandes (Google  2019-08-05  2883) }
495aa969dbaef2 Andreea-Cristina Bernat 2014-03-18  2884  EXPORT_SYMBOL_GPL(kfree_call_rcu);

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