Messages in this thread | | | Date | Fri, 08 Aug 2008 10:13:36 +0800 | From | Li Zefan <> | Subject | Re: [PATCH] Resurect proper handling of maxcpus= kernel option |
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Max Krasnyansky wrpte: > Li Zefan wrote: >> Max.Krasnyansky@qualcomm.com wrote: >>> From: Max Krasnyansky <maxk@qualcomm.com> >>> >>> For some reason we had redundant parsers registered for maxcpus=. >>> One in init/main.c and another in arch/x86/smpboot.c >>> So I nuked the one in arch/x86. >>> >>> Also 64-bit kernels used to handle maxcpus= as documented in >>> Documentation/cpu-hotplug.txt. CPUs with 'id > maxcpus' are initialized >>> but not booted. 32-bit version for some reason ignored them even though >>> all the infrastructure for booting them later is there. >>> >>> In the current mainline both 64 and 32 bit versions are broken. I'm >>> too lazy to look through git history but I'm guessing it happened as >>> part of the i386 and x86_64 unification. >>> >>> This patch restores the correct behaviour. I've tested x86_64 version on >>> 4- and 8- way Core2 and 2-way Opteron based machines. Various config >>> combinations SMP, !SMP, CPU_HOTPLUG, !CPU_HOTPLUG. >>> Booted with maxcpus=1 and maxcpus=4, etc. Everything is working as expected. >>> >>> I cannot test 32-bit version (no 32-bit machines here). >>> >> I booted my 2-core x86_32 box with maxcpus=1, and saw cpu1 was offline, >> and then I got softlockup BUG immediately when I onlined cpu1: >> >> SMP alternatives: switching to SMP code >> CPU 1 irqstacks, hard=c078c000 soft=c076c000 >> Booting processor 1/1 ip 6000 >> Initializing CPU#1 >> Calibrating delay using timer specific routine.. 5600.37 BogoMIPS (lpj=2800188) >> CPU: Trace cache: 12K uops, L1 D cache: 16K >> CPU: L2 cache: 1024K >> CPU: Physical Processor ID: 0 >> CPU: Processor Core ID: 1 >> Intel machine check architecture supported. >> Intel machine check reporting enabled on CPU#1. >> CPU1: Intel P4/Xeon Extended MCE MSRs (24) available >> CPU1: Thermal monitoring enabled >> CPU1: Intel(R) Pentium(R) D CPU 2.80GHz stepping 04 >> checking TSC synchronization [CPU#0 -> CPU#1]: passed. >> Switched to high resolution mode on CPU 1 >> BUG: soft lockup - CPU#1 stuck for 216s! [events/0:0] >> Modules linked in: bridge stp llc autofs4 dm_mirror dm_log dm_mod snd_intel8x0 snd_ac97_codec ac97_bus snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_pcm snd_timer snd soundcore r8169 snd_page_alloc sg button sata_sis pata_sis ata_generic libata sd_mod scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: scsi_wait_scan] >> irq event stamp: 156 >> hardirqs last enabled at (155): [<c044407f>] trace_hardirqs_on+0xb/0xd >> hardirqs last disabled at (156): [<c04eee88>] trace_hardirqs_off_thunk+0xc/0x10 >> softirqs last enabled at (152): [<c042c2f3>] __do_softirq+0xe3/0xe9 >> softirqs last disabled at (95): [<c04058eb>] do_softirq+0x65/0xb4 >> >> Pid: 0, comm: events/0 Not tainted (2.6.27-rc1 #224) >> EIP: 0060:[<c04088ba>] EFLAGS: 00000246 CPU: 1 >> EIP is at mwait_idle+0x3c/0x4a >> EAX: 00000000 EBX: e3e48008 ECX: 00000000 EDX: 00000000 >> ESI: 00000000 EDI: 00000000 EBP: e3e48f9c ESP: e3e48f98 >> DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 >> CR0: 8005003b CR2: 00000000 CR3: 00768000 CR4: 000006d0 >> DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 >> DR6: ffff0ff0 DR7: 00000400 >> [<c0402591>] cpu_idle+0xbf/0xdf >> [<c05fb737>] start_secondary+0x16b/0x170 >> ======================= >> >> >> 216s should be the time since the machine booted up. >> >> >> (maybe off-topic) >> I never succeed to offline cpu1, it caused the kernel to hang >> whenver I offlined cpu1 > > This is unrelated to the patch that I sent. In fact looks like the patch > actually worked for you. In the sense that it did the right thing, > initialized cpus but did not boot them. > > As far as the soft-lockup goes you might want to try different configs. > ie Disable features you do not need. For example cpusets hotplug path in > the current mainline is unsafe (the patch is in review). Also for me if > ftrace is enabled onlining a cpu causes immediate reboot. So I'd say > start disabling features and see which one cases the problem. >
Yes, the patch works for me, and the soft-lockup is another different issue. Thx for the explanation. :)
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