Il Mon, Jun 11, 2007 at 10:44:45AM +0300, Avi Kivity ha scritto: > Luca wrote: > >> > >>I've managed to reproduce this on kvm-21 (it takes many boots for this > >>to happen, but it does eventually). > > > >Hum, any clue on the cause? > > From what I've seen, it's the new Linux clocksource code. > > >Should I test older versions? > > They're unlikely to be better. Instead, it would be best to see what > the guest is doing.
RCU is not working. Network initialization hangs because it happens to be the first RCU user. The guest is stuck waiting for RCU syncronization: [ 4.992207] [<c04321c5>] synchronize_rcu+0x4e/0x80 [ 4.994379] [<c0431db5>] wakeme_after_rcu+0x0/0x8 [ 4.996521] [<c0599ad1>] synchronize_net+0x64/0x8c [ 4.998678] [<c05d70e0>] inet_register_protosw+0xef/0x151 [ 5.000984] [<c072d79e>] inet_init+0x1cd/0x498 wait_for_completion() in synchronize_rcu() calls schedule() and the completion is never signaled (wakeme_after_rcu is never called). The completion AFAICS would be signaled via rcu_process_callbacks(), which is called in tasklet context. Scheduler and completion are working fine since they're used in other part of the kernel without problems. To recap: i686 F7 kernel: always works. i586 F7 kernel: sometime hangs due to RCU problems. When it does work it's because the LAPIC is disabled on boot: Using local APIC timer interrupts. calibrating APIC timer ... ... lapic delta = 25745109 ... PM timer delta = 0 ..... delta 25745109 ..... mult: 1105912110 ..... calibration result: 4119217 ..... CPU clock speed is 8794.0417 MHz. ..... host bus clock speed is 4119.0217 MHz. ... verify APIC timer ... jiffies delta = 103 APIC timer disabled due to verification failure. When it doesn't work LAPIC passes the test: [ 1.304717] Using local APIC timer interrupts. [ 1.304719] calibrating APIC timer ... [ 1.718823] ... lapic delta = 25251444 [ 1.720582] ... PM timer delta = 0 [ 1.722219] ..... delta 25251444 [ 1.723827] ..... mult: 1084706136 [ 1.725470] ..... calibration result: 4040231 [ 1.727374] ..... CPU clock speed is 8625.0780 MHz. [ 1.729396] ..... host bus clock speed is 4040.0231 MHz. [ 1.731540] ... verify APIC timer [ 2.158342] ... jiffies delta = 102 [ 2.160035] ... jiffies result ok i586 F7 kernel, with 'nolapic': always works. Luca -- Sbagliare รจ umano, ma per incasinare davvero le cose serve un computer. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
