Messages in this thread | | | Date | Thu, 17 Feb 2011 15:11:47 -0800 (PST) | Subject | Re: IGMP and rwlock: Dead ocurred again on TILEPro | From | David Miller <> |
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From: Chris Metcalf <cmetcalf@tilera.com> Date: Thu, 17 Feb 2011 18:04:13 -0500
> On 2/17/2011 5:53 PM, David Miller wrote: >> From: Chris Metcalf <cmetcalf@tilera.com> >> Date: Thu, 17 Feb 2011 17:49:46 -0500 >> >>> The fix is to disable interrupts for the arch_read_lock family of methods. >> How does that help handle the race when it happens between different >> cpus, instead of between IRQ and non-IRQ context on the same CPU? > > There's no race in that case, since the lock code properly backs off and > retries until the other cpu frees it. The distinction here is that the > non-IRQ context is "wedged" by the IRQ context. > >> Why don't you just use the generic spinlock based rwlock code on Tile, >> since that is all that your atomic instructions can handle >> sufficiently? > > The tile-specific code encodes reader/writer information in the same 32-bit > word that the test-and-set instruction manipulates, so it's more efficient > both in space and time. This may not really matter for rwlocks, since no > one cares much about them any more, but that was the motivation.
Ok, but IRQ disabling is going to be very expensive.
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