Messages in this thread | | | Date | Thu, 26 Sep 2019 12:24:36 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [rcu:dev.2019.09.23a 62/77] kernel/rcu/tree.c:2882 kfree_call_rcu() warn: inconsistent returns 'irqsave:flags'. |
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On Thu, Sep 26, 2019 at 02:19:54PM -0400, Joel Fernandes wrote: > On Tue, Sep 24, 2019 at 09:03:48AM -0700, Paul E. McKenney wrote: > > On Tue, Sep 24, 2019 at 08:15:12AM -0400, Joel Fernandes wrote: > > > On Tue, Sep 24, 2019 at 4:05 AM Dan Carpenter <dan.carpenter@oracle.com> wrote: > > > > > > > > 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@intel.com> > > > > Reported-by: Dan Carpenter <dan.carpenter@oracle.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. > > > > > > Right. At this point the system has a bug anyway since it is a > > > double-free. But yes, no reason to introduce more bugs. Will fix. > > > Thank you, Dan! > > > > What Joel said! > > > > As long as I am doing several other reports anyway... > > > > How does the to-be-squashed patch below look? > > Hi Paul, > > Sorry for the late reply due to the conference.. > > This patch looks Ok, the code in your tree though is slightly different mine > I think because you reworked the kfree_rcu() code for working during early > boot.
Yes, I did pull some of the changes earlier.
> After my talk tomorrow, I will go through your rcu/dev tree in detail to > review the reworks you did in detail.
Sounds good, and best of everything with the talk!
> Let me know if you have the kfree_rcu() changes in a separate topic branch, > as well. So it will make reviewing easier.
They will be, shortly after -rc1 comes out.
Thanx, Paul
> thanks, > > - Joel > > > > > > Thanx, Paul > > > > ------------------------------------------------------------------------ > > > > commit 39af4c08038a8a6a7b1c9804fdd2c1921d583222 > > Author: Paul E. McKenney <paulmck@kernel.org> > > Date: Tue Sep 24 09:02:00 2019 -0700 > > > > squash! rcu: Add support for debug_objects debugging for kfree_rcu() > > > > [ paulmck: Fix IRQ per kbuild test robot <lkp@intel.com> feedback. ] > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 921daa7..edb7539 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -2870,7 +2870,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > // Probable double kfree_rcu(), just leak. > > WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n", > > __func__, head); > > - return; > > + goto unlock_return; > > } > > head->func = func; > > head->next = krcp->head; > > @@ -2883,6 +2883,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > > schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES); > > } > > > > +unlock_return: > > if (krcp->initialized) > > spin_unlock(&krcp->lock); > > local_irq_restore(flags);
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