• Peter Zijlstra's avatar
    lockdep: Fix the module unload key range freeing logic · 35a9393c
    Peter Zijlstra authored
    Module unload calls lockdep_free_key_range(), which removes entries
    from the data structures. Most of the lockdep code OTOH assumes the
    data structures are append only; in specific see the comments in
    add_lock_to_list() and look_up_lock_class().
    
    Clearly this has only worked by accident; make it work proper. The
    actual scenario to make it go boom would involve the memory freed by
    the module unlock being re-allocated and re-used for a lock inside of
    a rcu-sched grace period. This is a very unlikely scenario, still
    better plug the hole.
    
    Use RCU list iteration in all places and ammend the comments.
    
    Change lockdep_free_key_range() to issue a sync_sched() between
    removal from the lists and returning -- which results in the memory
    being freed. Further ensure the callers are placed correctly and
    comment the requirements.
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Andrey Tsyvarev <tsyvarev@ispras.ru>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
    35a9393c
module.c 98 KB