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Date: Fri, 27 Aug 2010 22:01:18 -0700 From: "Luck, Tony" <tony.luck@...el.com> To: Hedi Berriche <hedi@....com> CC: Petr Tesarik <ptesarik@...e.cz>, "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: RE: Serious problem with ticket spinlocks on ia64 >*Hasty* look seems to suggest that keeping the fancy asm bits but compiling >with >-O2 -frename-registers makes it work equally well. > >Don't take my word for it though, double check it, it's been a long week and >brain is anything but alert at this time of the night. Yup - that makes the usermode version run just fine (no problems in the first billion lock/unlock operations ... which is quite a lot of wrap-arounds of the 15-bit ticket lock). And since we already use -frename-registers when building the kernel, no immediate help for the kernel problem. :-( I may tinker with this test a bit to include some short random amounts of hold-time for the lock, and delays between attempts to acquire it (to make it look more like a contended kernel lock and less like a continuous queue of processes trading around a lock that is never free ... Petr's debug information definitely showed the lock becoming free at the wraparound (lock == 0x0). -Tony -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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