Hello. Al Viro wrote: > sysfs_get_dentry(), > mutex_lock(&parent->d_inode->i_mutex); > hitting parent->d_inode either NULL or very close to it, depending on your > .config; most likely NULL, if offset of i_mutex is 0xb8 in your build. > That's plausible - 0xb8 is what you'd get on UP build without spinlock > debugging, lockdep, etc. > > Assuming that this is what we get, everything looks explainable - we > have sysfs_rename_dir() calling sysfs_get_dentry() while the parent > gets evicted. We don't have any exclusion, so while we are playing > silly buggers with lookups in sysfs_get_dentry() we have parent become > negative; the rest is obvious...
That part of code is walking down the sysfs tree from the s_root of sysfs hierarchy and on each step parent is held using dget() while being referenced, so I don't think they can turn negative there. > AFAICS, the locking here is quite broken and frankly, sysfs_get_dentry() > and the way it plays with fs/namei.c are ucking fugly. Can you elaborate a bit? The locking in sysfs is unconventional but that's mostly from necessity. It has dual interface - vfs and driver model && vfs data structures (dentry and inode) are too big to always keep around, so it basically becomes a small distributed file system where the backing data can change asynchronously. > Could you stick > if (!parent->d_inode) > printk(KERN_WARNING "sysfs locking blows: %s", > parent->d_name.name); > right before > mutex_lock(&parent->d_inode->i_mutex); > dentry = lookup_one_noperm(cur->s_name, parent); > mutex_unlock(&parent->d_inode->i_mutex); > in sysfs_get_dentry() (fs/sysfs/dir.c) and verify that it does, indeed, > trigger? Yes, please. Thanks. -- 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/
