r8169: avoid NAPI scheduling delay.
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: Francois Romieu <romieu@fr.zoreil.com> Reported-by: Dave Jones <davej@redhat.com> Tested-by: Marc Dionne <marc.c.dionne@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Hayes Wang <hayeswang@realtek.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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