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Subject[v2 075/115] sysctl: move removal from list out of start_unregistering
Date
Later on we'll switch form a global list protected by the sysctl_lock
spin lock to rwsem protected per-header lists.

At that point we'll need to hold the parent header's rwlock to remove
the header from the list, not the sysctl_lock spin lock.

As start_unregistering is called under the sysctl_lock, we move the
list removal out.

Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
---
kernel/sysctl.c | 12 +++++++-----
1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8dde087..a863b56 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1552,11 +1552,6 @@ static void start_unregistering(struct ctl_table_header *p)
/* anything non-NULL; we'll never dereference it */
p->unregistering = ERR_PTR(-EINVAL);
}
- /*
- * do not remove from the list until nobody holds it; walking the
- * list in do_sysctl() relies on that.
- */
- list_del_init(&p->ctl_entry);
}

void sysctl_proc_inode_get(struct ctl_table_header *head)
@@ -1949,6 +1944,13 @@ void unregister_sysctl_table(struct ctl_table_header * header)

spin_lock(&sysctl_lock);
start_unregistering(header);
+
+ /* after start_unregistering has finished no one holds a
+ * ctl_use_refs or is able to acquire one => no one is going
+ * to access internal fields of this object, so we can remove
+ * it from the list and schedule it for deletion. */
+ list_del_init(&p->ctl_entry);
+
if (!--header->parent->ctl_header_refs) {
WARN_ON(1);
if (!header->parent->ctl_procfs_refs)
--
1.7.5.134.g1c08b


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