• Konrad Rzeszutek Wilk's avatar
    xen: Do not enable spinlocks before jump_label_init() has executed · a945928e
    Konrad Rzeszutek Wilk authored
    xen_init_spinlocks() currently calls static_key_slow_inc() before
    jump_label_init() is invoked. When CONFIG_JUMP_LABEL is set (which usually is
    the case) the effect of this static_key_slow_inc() is deferred until after
    jump_label_init(). This is different from when CONFIG_JUMP_LABEL is not set, in
    which case the key is set immediately. Thus, depending on the value of config
    option, we may observe different behavior.
    
    In addition, when we come to __jump_label_transform() from jump_label_init(),
    the key (paravirt_ticketlocks_enabled) is already enabled. On processors where
    ideal_nop is not the same as default_nop this will cause a BUG() since it is
    expected that before a key is enabled the latter is replaced by the former
    during initialization.
    
    To address this problem we need to move
    static_key_slow_inc(&paravirt_ticketlocks_enabled) so that it is called
    after jump_label_init(). We also need to make sure that this is done before
    other cpus start to boot. early_initcall appears to be  a good place to do so.
    (Note that we cannot move whole xen_init_spinlocks() there since pv_lock_ops
    need to be set before alternative_instructions() runs.)
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    [v2: Added extra comments in the code]
    Signed-off-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
    Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Reviewed-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    a945928e
spinlock.c 8.1 KB