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Marcin Slusarz reported a ne2k-pci "hung network interface" regression. delayed disable relies on the ability to re-trigger the interrupt in the case that a real interrupt happens after the software disable was set. In this case we actually disable the interrupt on the hardware level _after_ it occurred. On enable_irq, we need to re-trigger the interrupt. On i386 this relies on a hardware resend mechanism (send_IPI_self()). Actually we only need the resend for edge type interrupts. Level type interrupts come back once enable_irq() re-enables the interrupt line. I assume that the interrupt in question is level triggered because it is shared and above the legacy irqs 0-15: 17: 12 IO-APIC-fasteoi eth1, eth0 Looking into the IO_APIC code, the resend via send_IPI_self() happens unconditionally. So the resend is done for level and edge interrupts. This makes the problem more mysterious. The code in question lib8390.c does disable_irq(); fiddle_with_the_network_card_hardware() enable_irq(); The fiddle_with_the_network_card_hardware() might cause interrupts, which are cleared in the same code path again, Marcin found that when he disables the irq line on the hardware level (removing the delayed disable) the card is kept alive. So the difference is that we can get a resend on enable_irq, when an interrupt happens during the time, where we are in the disabled region. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| manage.c | ||
| migration.c | ||
| proc.c | ||
| resend.c | ||
| spurious.c | ||