Messages in this thread Patch in this message | | | Subject | Re: [regression 2.6.27.10 & 2.6.28] \"nolapic\" option causes \"nosmp\"? | From | Tetsuo Handa <> | Date | Tue, 06 Jan 2009 11:06:50 +0900 |
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Hello.
Maciej W. Rozycki wrote: > This is correct behaviour. The hardware uses the local APIC to > communicate between CPUs. With the subsystem disabled there is no way to > reach secondary CPUs on a standard x86 system.
Oh, I didn't know that. Then, the problem is use of "for_each_possible_cpu".
--- drivers/net/loopback.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- linux-2.6.28.orig/drivers/net/loopback.c +++ linux-2.6.28/drivers/net/loopback.c @@ -92,28 +92,35 @@ static int loopback_xmit(struct sk_buff static struct net_device_stats *get_stats(struct net_device *dev) { const struct pcpu_lstats *pcpu_lstats; struct net_device_stats *stats = &dev->stats; unsigned long bytes = 0; unsigned long packets = 0; int i; + printk(KERN_INFO "Entering get_stats()\n"); pcpu_lstats = dev->ml_priv; for_each_possible_cpu(i) { const struct pcpu_lstats *lb_stats; + printk(KERN_INFO "CPU=%u\n", i); lb_stats = per_cpu_ptr(pcpu_lstats, i); + if (!lb_stats) { + printk(KERN_INFO "lb_stats == NULL for CPU %u\n", i); + continue; + } bytes += lb_stats->bytes; packets += lb_stats->packets; } stats->rx_packets = packets; stats->tx_packets = packets; stats->rx_bytes = bytes; stats->tx_bytes = bytes; + printk(KERN_INFO "Leaving get_stats()\n"); return stats; } static u32 always_on(struct net_device *dev) { return 1; } Applying the above patch and compiling with config at http://I-love.SAKURA.ne.jp/tmp/config-2.6.28 and booting with "nolapic" produces below output.
---------------------------------------- BIOS EBDA/lowmem at: 0009f800/0009f800 Linux version 2.6.28 (root@tomoyo) (gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)) #1 SMP Tue Jan 6 10:18:14 JST 2009 (..... snipped .....) Kernel command line: ro root=LABEL=/ nolapic (..... snipped .....) ACPI: bus type pnp registered pnp: PnP ACPI: found 13 devices ACPI: ACPI bus type pnp unregistered system 00:01: ioport range 0x1000-0x103f has been reserved system 00:01: ioport range 0x1040-0x104f has been reserved system 00:01: ioport range 0xcf0-0xcf1 has been reserved system 00:0c: ioport range 0x1060-0x107f has been reserved system 00:0c: iomem range 0xe0000000-0xefffffff has been reserved system 00:0c: iomem range 0xdb400000-0xdb5fffff has been reserved Entering get_stats() CPU=0 Leaving get_stats() pci 0000:00:01.0: PCI bridge, secondary bus 0000:01 pci 0000:00:01.0: IO window: disabled pci 0000:00:01.0: MEM window: disabled pci 0000:00:01.0: PREFETCH window: disabled (..... snipped .....) kjournald starting. Commit interval 5 seconds (..... snipped .....) device-mapper: uevent: version 1.0.3 device-mapper: ioctl: 4.14.0-ioctl (2008-04-23) initialised: dm-devel@redhat.com device-mapper: multipath: version 1.0.5 loaded EXT3 FS on sda1, internal journal Entering get_stats() CPU=0 CPU=1 lb_stats == NULL for CPU 1 Leaving get_stats() warning: process `kudzu' used the deprecated sysctl system call with 1.23. NET: Registered protocol family 10 lo: Disabled Privacy Extensions process `sysctl' is using deprecated sysctl (syscall) net.ipv6.neigh.default.retrans_time; Use net.ipv6.neigh.default.retrans_time_ms instead. Entering get_stats() CPU=0 CPU=1 lb_stats == NULL for CPU 1 Leaving get_stats() ---------------------------------------- When "nolapic" is given, it prints "lb_stats == NULL for CPU 1" message. If '"nolapic" disables CPU 1' is correct behavior, the "CPU=1" message should not be printed.
Regards.
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