Hi folks,I've stumbled across an interesting locking scheme. It's related to struct inode, more precisely it is an mqueue inode. Our results show that inode:mqueue.i_opflags is read with i_rwsem being hold. In d_flags_for_inode, and do_inode_permission the i_lock is used to read and write i_opflags.
Is this a real locking scheme? Is a lock needed to access i_opflags at all? What is the magic behind this contradiction?I've put the report of the counterexamples on our webserver: https://ess.cs.tu-dortmund.de/lockdoc-bugs/cex-inode-mqueue.html. It contains the stacktraces leading to those accesses, and the locks that were actually held.
Regards, Alex -- Technische Universität Dortmund Alexander Lochmann PGP key: 0xBC3EF6FD Otto-Hahn-Str. 16 phone: +49.231.7556141 D-44227 Dortmund fax: +49.231.7556116 http://ess.cs.tu-dortmund.de/Staff/al
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