diff options
| author | Qi Zheng <zhengqi.arch@bytedance.com> | 2023-02-02 18:56:12 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-09 15:56:51 -0800 |
| commit | badc28d4924bfed73efc93f716a0c3aa3afbdf6f (patch) | |
| tree | 71a94e24eaf573ef94b3544d5db872a15a5fef7d /mm/shrinker_debug.c | |
| parent | 6b970599e807ea95c653926d41b095a92fd381e2 (diff) | |
mm: shrinkers: fix deadlock in shrinker debugfs
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: 5035ebc644ae ("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>
Diffstat (limited to 'mm/shrinker_debug.c')
| -rw-r--r-- | mm/shrinker_debug.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c index b05295bab322..39c3491e28a3 100644 --- a/mm/shrinker_debug.c +++ b/mm/shrinker_debug.c @@ -246,18 +246,21 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...) } EXPORT_SYMBOL(shrinker_debugfs_rename); -void shrinker_debugfs_remove(struct shrinker *shrinker) +struct dentry *shrinker_debugfs_remove(struct shrinker *shrinker) { + struct dentry *entry = shrinker->debugfs_entry; + lockdep_assert_held(&shrinker_rwsem); kfree_const(shrinker->name); shrinker->name = NULL; - if (!shrinker->debugfs_entry) - return; + if (entry) { + ida_free(&shrinker_debugfs_ida, shrinker->debugfs_id); + shrinker->debugfs_entry = NULL; + } - debugfs_remove_recursive(shrinker->debugfs_entry); - ida_free(&shrinker_debugfs_ida, shrinker->debugfs_id); + return entry; } static int __init shrinker_debugfs_init(void) |