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commitbadc28d492upstream. The debugfs_remove_recursive() is invoked by unregister_shrinker(), which is holding the write lock of shrinker_rwsem. It will waits for the handler of debugfs file complete. The handler also needs to hold the read lock of shrinker_rwsem to do something. So it may cause the following deadlock: CPU0 CPU1 debugfs_file_get() shrinker_debugfs_count_show()/shrinker_debugfs_scan_write() unregister_shrinker() --> down_write(&shrinker_rwsem); debugfs_remove_recursive() // wait for (A) --> wait_for_completion(); // wait for (B) --> down_read_killable(&shrinker_rwsem) debugfs_file_put() -- (A) up_write() -- (B) The down_read_killable() can be killed, so that the above deadlock can be recovered. But it still requires an extra kill action, otherwise it will block all subsequent shrinker-related operations, so it's better to fix it. [akpm@linux-foundation.org: fix CONFIG_SHRINKER_DEBUG=n stub] Link: https://lkml.kernel.org/r/20230202105612.64641-1-zhengqi.arch@bytedance.com Fixes:5035ebc644("mm: shrinkers: introduce debugfs interface for memory shrinkers") Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com> Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.