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 <[email protected]>
Reported-by: [email protected]
Tested-by: Zhouyi Zhou <[email protected]>
Signed-off-by: Chengming Zhou <[email protected]>
---
include/linux/cgroup.h | 1 +
1 file changed, 1 insertion(+)
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))
--
2.20.1
On 05.03.2022 04:41, Chengming Zhou wrote:
> 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 <[email protected]>
> Reported-by: [email protected]
> Tested-by: Zhouyi Zhou <[email protected]>
> Signed-off-by: Chengming Zhou <[email protected]>
Right, this fixes the issue I've reported here:
https://lore.kernel.org/all/[email protected]/
Tested-by: Marek Szyprowski <[email protected]>
> ---
> include/linux/cgroup.h | 1 +
> 1 file changed, 1 insertion(+)
>
> 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))
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
On Sat, Mar 05, 2022 at 11:41:03AM +0800, Chengming Zhou wrote:
> 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 <[email protected]>
> Reported-by: [email protected]
> Tested-by: Zhouyi Zhou <[email protected]>
> Signed-off-by: Chengming Zhou <[email protected]>
> ---
> include/linux/cgroup.h | 1 +
> 1 file changed, 1 insertion(+)
>
> 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))
Acked-by: Tejun Heo <[email protected]>
Thanks.
--
tejun
On Sat, Mar 05, 2022 at 11:41:03AM +0800, Chengming Zhou wrote:
> 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 <[email protected]>
> Reported-by: [email protected]
> Tested-by: Zhouyi Zhou <[email protected]>
> Signed-off-by: Chengming Zhou <[email protected]>
Thanks, I'll go stick this in sched/core so it's in the same branch that
caused the problem.
On Sat, Mar 12, 2022 at 01:19:13PM +0100, Peter Zijlstra wrote:
> On Sat, Mar 05, 2022 at 11:41:03AM +0800, Chengming Zhou wrote:
> > 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 <[email protected]>
> > Reported-by: [email protected]
> > Tested-by: Zhouyi Zhou <[email protected]>
> > Signed-off-by: Chengming Zhou <[email protected]>
>
> Thanks, I'll go stick this in sched/core so it's in the same branch that
> caused the problem.
FWIW I never saw this patch because it doesn't instantly look like a
patch I should be interested in. It's classified as 'for-next' and I
don't run -next, sfr does that. Then it's tagged as cgroup, which I also
don't do.
Nowhere does that look like a patch that wants to go in sched/core and
fixes a cpuacct issue.
On top of that, I still don't agree with this, I really think
rcu_dereference_check() itself should be changed.
The following commit has been merged into the sched/core branch of tip:
Commit-ID: f2aa197e4794bf4c2c0c9570684f86e6fa103e8b
Gitweb: https://git.kernel.org/tip/f2aa197e4794bf4c2c0c9570684f86e6fa103e8b
Author: Chengming Zhou <[email protected]>
AuthorDate: Sat, 05 Mar 2022 11:41:03 +08:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Sat, 12 Mar 2022 13:22:11 +01:00
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 <[email protected]>
Reported-by: [email protected]
Signed-off-by: Chengming Zhou <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Tested-by: Zhouyi Zhou <[email protected]>
Tested-by: Marek Szyprowski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
include/linux/cgroup.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 1e356c2..0d1ada8 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))