Re: [BUG,2.6.28,s390] Fails to boot in Hercules S/390 emulator - hang traced

Frans Pop
2009-03-13T17:34:46Z

On Friday 13 March 2009, Frans Pop wrote:
> I added printks that show changes in clock data. I print info for
> 3 consecutive calls of update_wall_time every 1000 times the function
> is called and also after a change of clock source.

Aaarghh. I'm a moron, but most of you will already have concluded that by
now. I've been looking at nsecs as if they also included secs.

So, here's a trace with Roman's patches that really shows the relevant
data. Basic conclusion remains the same though: time really does look to
be running backwards in the very early part of the boot because the
seconds are not advancing while the nsecs are going backwards.

0.004688! jiffies/8 (1): xtime.tv: 1236962306/99461000 -> 1236962306/99461001
0.004793! clock->xtime: 0 -> -256, error: 0 -> -4294867296
0.009705! jiffies/8 (2): xtime.tv: 1236962306/99461001 -> 1236962306/99444618
0.009821! clock->xtime: -256 -> -256, error: -4294867296 -> -4292501984672096
0.014514! Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
0.014944! jiffies/8 (3): xtime.tv: 1236962306/99444618 -> 1236962306/99395467
0.015067! clock->xtime: -256 -> -256, error: -4292501984672096 -> -12807124325236736
0.019704! jiffies/8 (4): xtime.tv: 1236962306/99395467 -> 1236962306/99379084
0.019811! clock->xtime: -256 -> -256, error: -12807124325236736 -> -14918180945433952
0.140556! Memory: 251008k/262144k available (2144k kernel code, 0k reserved, 897k data, 152k init)
0.140913! Write protected kernel read-only data: 0x12000 - 0x2d8fff
0.143231! Calibrating delay loop (skipped)... 572.00 BogoMIPS preset
0.144675! Security Framework initialized
0.144870! SELinux: Disabled at boot.
0.146009! Mount-cache hash table entries: 512
0.152474! Initializing cgroup subsys ns
0.152671! Initializing cgroup subsys cpuacct
0.153095! Initializing cgroup subsys devices
0.154303! init: calling smp_prepare_cpus
0.189342! CPUs: 2 configured, 0 standby
0.189516! s390_smp: smp_detect_cpus calling get_online_cpus
0.189742! s390_smp: smp_detect_cpus calling __smp_rescan_cpus
0.189964! s390_smp: smp_rescan_cpus_sigp starting loop
[... System hangs here ...]

[... By this time it looks like the error has stabilized somewhat and nsecs are more stable ...]
[... nsecs are actually larger now than in the display at 0.019704 ...]
0.311447! jiffies/8 (153): xtime.tv: 1236962306/599346640 -> 1236962306/599346640
0.311567! clock->xtime: -228 -> -29, error: -16490881133476192 -> -16490883213850976
0.312174! jiffies/8 (154): xtime.tv: 1236962306/599346640 -> 1236962306/599346641
0.312292! clock->xtime: -29 -> -226, error: -16490883213850976 -> -16490885428443488
0.312884! jiffies/8 (155): xtime.tv: 1236962306/599346641 -> 1236962306/599346641
0.313014! clock->xtime: -226 -> -31, error: -16490885428443488 -> -16490887508818272
[... Only here do seconds start to increase ...]
0.320129! jiffies/8 (304): xtime.tv: 1236962307/99331656 -> 1236962307/99331656
0.320254! clock->xtime: -201 -> -56, error: -16426767068861792 -> -16426769149236576
0.320844! jiffies/8 (305): xtime.tv: 1236962307/99331656 -> 1236962307/99331657
0.320954! clock->xtime: -56 -> -199, error: -16426769149236576 -> -16426781363829088
0.321536! jiffies/8 (306): xtime.tv: 1236962307/99331657 -> 1236962307/99331657
0.321651! clock->xtime: -199 -> -58, error: -16426781363829088 -> -16426783444203872
0.328758! jiffies/8 (455): xtime.tv: 1236962307/599316731 -> 1236962307/599316732
0.328876! clock->xtime: -82 -> -173, error: -16362926407417856 -> -16362928622010368
0.329470! jiffies/8 (456): xtime.tv: 1236962307/599316732 -> 1236962307/599316732
0.329598! clock->xtime: -173 -> -84, error: -16362928622010368 -> -16362920702285152
0.330192! jiffies/8 (457): xtime.tv: 1236962307/599316732 -> 1236962307/599316733
0.330317! clock->xtime: -84 -> -171, error: -16362920702285152 -> -16362922916877664
0.374500! jiffies/8 (1456): xtime.tv: 1236962311/599199308 -> 1236962311/599199308
0.374632! clock->xtime: -165 -> -92, error: -15860566497065312 -> -15860568577440096