On Fri, 2017-03-17 at 17:10 +0000, Marc Zyngier wrote: > > > > > > > > > FWIW if I trigger a crash on CPU 1 my kdump (still 4.9.8+v32) doesn't work. > > > > I end up booting the kdump kernel on CPU#1 and then it gets distinctly unhappy... > > > > > > > > [????0.000000] Booting Linux on physical CPU 0x1 > > > > ... > > > > [????0.017125] Detected PIPT I-cache on CPU1 > > > > [????0.017138] GICv3: CPU1: found redistributor 0 region 0:0x00000000f0280000 > > > > [????0.017147] CPU1: Booted secondary processor [411fd073] > > > > [????0.017339] Detected PIPT I-cache on CPU2 > > > > [????0.017347] GICv3: CPU2: found redistributor 2 region 0:0x00000000f02c0000 > > > > [????0.017354] CPU2: Booted secondary processor [411fd073] > > > > [????0.017537] Detected PIPT I-cache on CPU3 > > > > [????0.017545] GICv3: CPU3: found redistributor 3 region 0:0x00000000f02e0000 > > > > [????0.017551] CPU3: Booted secondary processor [411fd073] > > > > [????0.017576] Brought up 4 CPUs > > > > [????0.017587] SMP: Total of 4 processors activated. > > > > ... > > > > [???31.745809] INFO: rcu_sched detected stalls on CPUs/tasks: > > > > [???31.751299]? 1-...: (30 GPs behind) idle=c90/0/0 softirq=0/0 fqs=0? > > > > [???31.757557]? 2-...: (30 GPs behind) idle=608/0/0 softirq=0/0 fqs=0? > > > > [???31.763814]? 3-...: (30 GPs behind) idle=604/0/0 softirq=0/0 fqs=0? > > > > [???31.770069]? (detected by 0, t=5252 jiffies, g=-270, c=-271, q=0) > > > > [???31.776161] Task dump for CPU 1: > > > > [???31.779381] swapper/1???????R??running task????????0?????0??????1 0x00000080 > > > > [???31.786446] Task dump for CPU 2: > > > > [???31.789666] swapper/2???????R??running task????????0?????0??????1 0x00000080 > > > > [???31.796725] Task dump for CPU 3: > > > > [???31.799945] swapper/3???????R??running task????????0?????0??????1 0x00000080 > > > > > > > > Is some of that platform-specific? > > > That sounds like timer interrupts aren't being taken. > > > > > > Given that the CPUs have come up, my suspicion would be that the GIC's > > > been left in some odd state, that the kdump kernel hasn't managed to > > > recover from. > > > > > > Marc may have an idea. > > I thought kdump was UP only? Anyway, this doesn't look too good. > > > > It would be interesting to find out whether we're still taking > > interrupts. Also, being able to reproduce this on mainline would be useful. > > > > I wonder if we don't have a bug when booting on something other than > > CPU#0, possibly on a GICv3 platform... I'll give it a go. > Went ahead and tried a couple of kexecs with various CPUs disabled in > order to force kexec not to boot on CPU#0, and the VM did boot just fine. > > So I'd really appreciate a mainline reproducer. I booted an up-to-date 4.11-rc2 kernel with the v33 patch set. I cannot reproduce. But then again, I can't reproduce it on 4.9 *either* any more. And that is precisely the same kernel image I uploaded earlier. So it appears to be sporadic, and just *happened* to hit me the first time I tried... which is probably just as well or I'd never have tried that again :) I'll keep trying. -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/x-pkcs7-signature Size: 4938 bytes Desc: not available URL: <http://lists.infradead.org/pipermail/kexec/attachments/20170317/a232a3dc/attachment.bin>
