Re: [patch] SMP race fix [was Re: SMP lockup & 3c509 on 2.2.x [aka. the Deadly 'ping -f']]

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 6 May 1999 02:24:17 +0100 (BST)

> However, the above use of synchronize_irq() may not actually be physically
> possible (for the simple reason that the device and the CPU really aren't
> synchronized ina very real sense, and there is nothing we can do at a low

Its demonstrably not doable. I had to work around the APIC latency with the
8390 driver.

I ended up doing

disable_irq(blah)
synchronize_irq();

spin_lock(...)

Simply trying to stop the irq on the card didnt work. Sometimes one was
hiding.

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