• françois romieu's avatar
    r8169: avoid NAPI scheduling delay. · 7dbb4918
    françois romieu authored
    While reworking the r8169 driver a few months ago to perform the
    smallest amount of work in the irq handler, I took care of avoiding
    any irq mask register operation in the slow work dedicated user
    context thread. The slow work thread scheduled an extra round of NAPI
    work which would ultimately set the irq mask register as required,
    thus keeping such irq mask operations in the NAPI handler.
    It would eventually race with the irq handler and delay NAPI execution
    for - assuming no further irq - a whole ksoftirqd period. Mildly a
    problem for rare link changes or corner case PCI events.
    
    The race was always lost after the last bh disabling lock had been
    removed from the work thread and people started wondering where those
    pesky "NOHZ: local_softirq_pending 08" messages came from.
    
    Actually the irq mask register _can_ be set up directly in the slow
    work thread.
    Signed-off-by: default avatarFrancois Romieu <romieu@fr.zoreil.com>
    Reported-by: default avatarDave Jones <davej@redhat.com>
    Tested-by: default avatarMarc Dionne <marc.c.dionne@gmail.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Hayes Wang <hayeswang@realtek.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    7dbb4918
r8169.c 159 KB