Re: [PATCH 12/25] sysfs: Introduce sysfs_rename_mutex

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Tejun Heo wrote:
> 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

Oops, forget about the above.  Thought the comment was added to
sysfs_rename_dir().

-- 
tejun
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux