Hao Luo 1a702dc88e kernfs: Separate kernfs_pr_cont_buf and rename_lock. ... Previously the protection of kernfs_pr_cont_buf was piggy backed by rename_lock, which means that pr_cont() needs to be protected under rename_lock. This can cause potential circular lock dependencies. If there is an OOM, we have the following call hierarchy: -> cpuset_print_current_mems_allowed() -> pr_cont_cgroup_name() -> pr_cont_kernfs_name() pr_cont_kernfs_name() will grab rename_lock and call printk. So we have the following lock dependencies: kernfs_rename_lock -> console_sem Sometimes, printk does a wakeup before releasing console_sem, which has the dependence chain: console_sem -> p->pi_lock -> rq->lock Now, imagine one wants to read cgroup_name under rq->lock, for example, printing cgroup_name in a tracepoint in the scheduler code. They will be holding rq->lock and take rename_lock: rq->lock -> kernfs_rename_lock Now they will deadlock. A prevention to this circular lock dependency is to separate the protection of pr_cont_buf from rename_lock. In principle, rename_lock is to protect the integrity of cgroup name when copying to buf. Once pr_cont_buf has got its content, rename_lock can be dropped. So it's safe to drop rename_lock after kernfs_name_locked (and kernfs_path_from_node_locked) and rely on a dedicated pr_cont_lock to protect pr_cont_buf. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Hao Luo <haoluo@google.com> Link: https://lore.kernel.org/r/20220516190951.3144144-1-haoluo@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-05-19 19:37:06 +02:00
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dir.c	kernfs: Separate kernfs_pr_cont_buf and rename_lock.	2022-05-19 19:37:06 +02:00
file.c	kernfs: Rename kernfs_put_open_node to kernfs_unlink_open_file.	2022-05-06 09:56:39 +02:00
inode.c
Kconfig
kernfs-internal.h
Makefile
mount.c
symlink.c