Date: Mon, 02 May 2011 16:13:20 -0500 From: Mike Karels <mike@karels.net> To: freebsd-amd64@freebsd.org Cc: mike_karels@mcafee.com Subject: variable hang when starting APs on Westmere processors Message-ID: <201105022113.p42LDLrl051285@mail.karels.net>
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Looks like freebsd-smp is gone... not sure of the right target for this. I just picked up a problem from another developer at work who had the good fortune to have scheduled a vacation this week. The short description is that the start_ap() routine sometimes hangs, from 10 minutes to 3 hours, while starting up CPUs. This is with a much-modified system based on FreeBSD 7.2. A stock 8.2 CD hangs at the same spot almost all the time, although the code in the two versions appears identical. More details: This is amd64, using an Intel S5520HCR 2-socket motherboard with two XEON X5660 2.8GHz Westmere hex-core CPUs. The problem happens somewhat less with two XEON E5620 Quad core 2.4GHz CPUs. The hang seems to happen with higher numbered CPUs, so the hex-core with SMT has more chances to hit the problem. We added KTRs to the code, and found that the hang happens in the lapic_ipi_wait() call after de-asserting RESET. Of course, Linux doesn't exhibit the problem. Has anyone else seen a problem like this? Any ideas how to fix it, or debug further? Please copy me on responses; I'm not subscribed to this list currently. Mike
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