Messages in this thread | | | Date | Wed, 08 Aug 2007 17:19:32 +0900 | From | Tejun Heo <> | Subject | Re: [PATCH 12/25] sysfs: Introduce sysfs_rename_mutex |
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Hello, Eric.
Eric W. Biederman wrote: > Looking carefully at the rename code we have a subtle dependency > that the structure of sysfs not change while we are performing > a rename. If the parent directory of the object we are renaming > changes while the rename is being performed nasty things could > happen when we go to release our locks. > > So introduce a sysfs_rename_mutex to prevent this highly > unlikely theoretical issue.
Yeah, it's a theoretical issue. Rename/move implementation has always depended on the parent structure not changing beneath it, but it's nice to tighten up loose ends.
> +DEFINE_MUTEX(sysfs_rename_mutex);
Probably doesn't really matter but wouldn't a rwsem fit better?
> @@ -774,7 +775,7 @@ static struct dentry *__sysfs_get_dentry(struct super_block *sb, struct sysfs_di > * down from there looking up dentry for each step. > * > * LOCKING: > - * Kernel thread context (may sleep) > + * mutex_lock(sysfs_rename_mutex)
LOCKING describes what locks should be held when entering the function, so proper description would be something like...
Kernel thread context, grabs sysfs_rename_mutex
Thanks.
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