On 10/19/23 15:08, Tejun Heo wrote:
On Thu, Oct 19, 2023 at 02:38:52PM +0800, Yafang Shao wrote:
- BUG_ON(!res_cgroup);
+ WARN_ON_ONCE(!res_cgroup && lockdep_is_held(&cgroup_mutex));
This doesn't work. lockdep_is_held() is always true if !PROVE_LOCKING.
will use mutex_is_locked() instead.
But then, someone else can hold the lock and trigger the condition
spuriously. The kernel doesn't track who's holding the lock unless lockdep
is enabled.
It is actually possible to detect if the current process is the owner of
a mutex since there is a owner field in the mutex structure. However,
the owner field also contains additional information which need to be
masked off before comparing with "current". If such a functionality is
really needed, we will have to add a helper function mutex_is_held(),
for example, to kernel/locking/mutex.c.
Cheers,
Longman
