svn commit: r233961 - head/sys/x86/x86

[Attilio Rao]

Il 09 aprile 2012 19:35, John Baldwin <jhb at freebsd.org> ha scritto:
> On Monday, April 09, 2012 1:59:13 pm Attilio Rao wrote:
>> Il 09 aprile 2012 18:14, John Baldwin <jhb at freebsd.org> ha scritto:
>> > On Monday, April 09, 2012 12:58:07 pm Attilio Rao wrote:
>> >> Il 09 aprile 2012 17:34, John Baldwin <jhb at freebsd.org> ha scritto:
>> >> > On Monday, April 09, 2012 11:45:11 am Jaakko Heinonen wrote:
>> >> >>
>> >> >> Hi,
>> >> >>
>> >> >> On 2012-04-06, Justin T. Gibbs wrote:
>> >> >> >   Fix interrupt load balancing regression, introduced in revision
>> >> >> >   222813, that left all un-pinned interrupts assigned to CPU 0.
>> >> >> >
>> >> >> >   sys/x86/x86/intr_machdep.c:
>> >> >> >     In intr_shuffle_irqs(), remove CPU_SETOF() call that initialized
>> >> >> >     the "intr_cpus" cpuset to only contain CPU0.
>> >> >> >
>> >> >> >     This initialization is too late and nullifies the results of calls
>> >> >> >     the intr_add_cpu() that occur much earlier in the boot process.
>> >> >> >     Since "intr_cpus" is statically initialized to the empty set, and
>> >> >> >     all processors, including the BSP, already add themselves to
>> >> >> >     "intr_cpus" no special initialization for the BSP is necessary.
>> >> >>
>> >> >> My Pentium 4 system hangs on boot after this commit. These are the last
>> >> >> lines from a verbose boot:
>> >> >>
>> >> >> SMP: AP CPU #1 Launched!
>> >> >> cpu1 AP:
>> >> >>      ID: 0x01000000   VER: 0x00050014 LDR: 0x00000000 DFR: 0xffffffff
>> >> >>   lint0: 0x00010700 lint1: 0x00000400 TPR: 0x00000000 SVR: 0x000001ff
>> >> >>   timer: 0x000100ef therm: 0x00010000 err: 0x000000f0 pmc: 0x00010400
>> >> >>
>> >> >> The system boots with r233960.
>> >> >>
>> >> >> Some information:
>> >> >>
>> >> >> CPU: Intel(R) Pentium(R) 4 CPU 2.60GHz (2605.96-MHz 686-class CPU)
>> >> >>   Origin = "GenuineIntel"  Id = 0xf29  Family = f  Model = 2  Stepping =
>> >> >> 9
>> >> >>
>> >> >
> Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
>> >> >>   Features2=0x4400<CNXT-ID,xTPR>
>> >> >> real memory  = 2147483648 (2048 MB)
>> >> >> avail memory = 2085228544 (1988 MB)
>> >> >> Event timer "LAPIC" quality 400
>> >> >> ACPI APIC Table: <A M I  OEMAPIC >
>> >> >> FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
>> >> >> FreeBSD/SMP: 1 package(s) x 1 core(s) x 2 HTT threads
>> >> >>  cpu0 (BSP): APIC ID:  0
>> >> >>  cpu1 (AP/HT): APIC ID:  1
>> >> >
>> >> > I suspect in your case intr_add_cpu() is never called.  I think Attilio is not
>> >> > correct in that it is not called for the BSP.
>> >> >
>> >> > Yes, it is not called for the BSP in set_interrupt_apic_ids().  This used to
>> >> > work because bit 0 was assigned statically.  Also, in a UP machine
>> >> > set_interrupt_apic_ids() is not called at all.
>> >>
>> >> But why there is a front-end check for the BSP in set_interrupt_apic_ids()?
>> >>
>> >> Anyway, I think a better fix would be like the attached patch.
>> >
>> > This would be fine.  What I would really prefer is to not need the sysinit at
>> > all and be able to do something like the original pre-cpuset code:
>> >
>> > static cpuset_t intr_cpus = CPU_INITIAILIZER(0);
>>
>> This is more difficult to do because it would require static array
>> initializations and it would pollute too much the code with compile
>> time, MAXCPU-dependant details.
>>
>> > Also, with the cpuset variant, I think we could remove the special case check
>> > for the BSP from set_apic_interrupt_ids() as it doesn't hurt to set it
>> > multiple times.   IIRC, the pre-cpuset code kept a separate count which is
>> > why that would have been harmful.
>>
>> I'm not sure I follow, a separate count for what?
>
> The pre-cpuset code used a separate count IIRC.  That is why duplicate calls
> to intr_add_cpu() used to be bad.  However, they are no longer bad.
>
>> So do you consider the following patch as a real commit candidate?
>
> Yes, modulo a nit:
>
>> Index: sys/i386/i386/machdep.c
>> ===================================================================
>> --- sys/i386/i386/machdep.c     (revisione 234064)
>> +++ sys/i386/i386/machdep.c     (copia locale)
>> @@ -336,6 +336,11 @@ cpu_startup(dummy)
>>  #ifndef XEN
>>         cpu_setregs();
>>  #endif
>> +
>> +       /*
>> +        * Add BSP interrupt bitmask.
>> +        */
>> +       intr_add_cpu(0);
>>  }
>
> I would make this a single line comment and say:
> "Add BSP as an interrupt target."

Please note that all the other comments in cpu_startup() is 3 lines
even when single so I'd stick with that.
I will change the wording as you wish though.

Attilio


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