Messages in this thread | | | Date | Wed, 16 Mar 2022 19:27:04 -0400 | From | "J. Bruce Fields" <> | Subject | Re: failure to boot after dc6e0818bc9a "sched/cpuacct: Optimize away RCU read lock" |
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On Wed, Mar 16, 2022 at 09:48:06PM +0100, Peter Zijlstra wrote: > On Wed, Mar 16, 2022 at 01:43:24PM -0400, J. Bruce Fields wrote: > > One of my test VMs has been failing to boot linux-next recently. I > > finally got around to a bisect this morning, and it landed on the below. > > > > What other information would be useful to debug this? > > A more recent -next should have this commit in it:
Ah, yep, it's booting again with today's -next. Thanks.--b.
> > > commit f2aa197e4794bf4c2c0c9570684f86e6fa103e8b > Author: Chengming Zhou <zhouchengming@bytedance.com> > Date: Sat Mar 5 11:41:03 2022 +0800 > > cgroup: Fix suspicious rcu_dereference_check() usage warning > > task_css_set_check() will use rcu_dereference_check() to check for > rcu_read_lock_held() on the read-side, which is not true after commit > dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock"). This > commit drop explicit rcu_read_lock(), change to RCU-sched read-side > critical section. So fix the RCU warning by adding check for > rcu_read_lock_sched_held(). > > Fixes: dc6e0818bc9a ("sched/cpuacct: Optimize away RCU read lock") > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org> > Reported-by: syzbot+16e3f2c77e7c5a0113f9@syzkaller.appspotmail.com > Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Acked-by: Tejun Heo <tj@kernel.org> > Tested-by: Zhouyi Zhou <zhouzhouyi@gmail.com> > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> > Link: https://lore.kernel.org/r/20220305034103.57123-1-zhouchengming@bytedance.com > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index 1e356c222756..0d1ada8968d7 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -450,6 +450,7 @@ extern struct mutex cgroup_mutex; > extern spinlock_t css_set_lock; > #define task_css_set_check(task, __c) \ > rcu_dereference_check((task)->cgroups, \ > + rcu_read_lock_sched_held() || \ > lockdep_is_held(&cgroup_mutex) || \ > lockdep_is_held(&css_set_lock) || \ > ((task)->flags & PF_EXITING) || (__c))
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