• Miroslav Benes's avatar
    livepatch: Remove immediate feature · d0807da7
    Miroslav Benes authored
    Immediate flag has been used to disable per-task consistency and patch
    all tasks immediately. It could be useful if the patch doesn't change any
    function or data semantics.
    
    However, it causes problems on its own. The consistency problem is
    currently broken with respect to immediate patches.
    
    func            a
    patches         1i
                    2i
                    3
    
    When the patch 3 is applied, only 2i function is checked (by stack
    checking facility). There might be a task sleeping in 1i though. Such
    task is migrated to 3, because we do not check 1i in
    klp_check_stack_func() at all.
    
    Coming atomic replace feature would be easier to implement and more
    reliable without immediate.
    
    Thus, remove immediate feature completely and save us from the problems.
    
    Note that force feature has the similar problem. However it is
    considered as a last resort. If used, administrator should not apply any
    new live patches and should plan for reboot into an updated kernel.
    
    The architectures would now need to provide HAVE_RELIABLE_STACKTRACE to
    fully support livepatch.
    Signed-off-by: 's avatarMiroslav Benes <mbenes@suse.cz>
    Acked-by: 's avatarJosh Poimboeuf <jpoimboe@redhat.com>
    Signed-off-by: 's avatarJiri Kosina <jkosina@suse.cz>
    d0807da7
livepatch.txt 20.6 KB