• Herbert Xu's avatar
    [NET]: Add netif_tx_lock · 932ff279
    Herbert Xu authored
    Various drivers use xmit_lock internally to synchronise with their
    transmission routines.  They do so without setting xmit_lock_owner.
    This is fine as long as netpoll is not in use.
    
    With netpoll it is possible for deadlocks to occur if xmit_lock_owner
    isn't set.  This is because if a printk occurs while xmit_lock is held
    and xmit_lock_owner is not set can cause netpoll to attempt to take
    xmit_lock recursively.
    
    While it is possible to resolve this by getting netpoll to use
    trylock, it is suboptimal because netpoll's sole objective is to
    maximise the chance of getting the printk out on the wire.  So
    delaying or dropping the message is to be avoided as much as possible.
    
    So the only alternative is to always set xmit_lock_owner.  The
    following patch does this by introducing the netif_tx_lock family of
    functions that take care of setting/unsetting xmit_lock_owner.
    
    I renamed xmit_lock to _xmit_lock to indicate that it should not be
    used directly.  I didn't provide irq versions of the netif_tx_lock
    functions since xmit_lock is meant to be a BH-disabling lock.
    
    This is pretty much a straight text substitution except for a small
    bug fix in winbond.  It currently uses
    netif_stop_queue/spin_unlock_wait to stop transmission.  This is
    unsafe as an IRQ can potentially wake up the queue.  So it is safer to
    use netif_tx_disable.
    
    The hamradio bits used spin_lock_irq but it is unnecessary as
    xmit_lock must never be taken in an IRQ handler.
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    932ff279
sch_generic.c 14.8 KB