Please CC me as I'm not subscribing to the list. Sometimes I get a kernel warning when disabling a CPU core. The one below came from a 3.2.48 kernel running on a VMware Workstation VM. I have also tried with kernels 3.4.52 and 3.10. Kernel 3.10 seems to hold although it not always allow to disable a CPU if it is in use.
The issue is easily reproducible in a couple of minutes if disabling/enabling in a loop like this (assuming a system with 4 cpus): ----- while [ true ] ; do echo "0" > /sys/devices/system/cpu/cpu3/online echo "0" > /sys/devices/system/cpu/cpu2/online echo "0" > /sys/devices/system/cpu/cpu1/online echo "1" > /sys/devices/system/cpu/cpu3/online echo "1" > /sys/devices/system/cpu/cpu2/online echo "1" > /sys/devices/system/cpu/cpu1/online done ----- I have seen different symptoms. The system may freeze, panic or just throw a kernel warning. ====================== Jul 8 12:12:12 ipam kernel: [ 68.128408] ------------[ cut here ]------------ Jul 8 12:12:12 ipam kernel: [ 68.128418] WARNING: at kernel/smp.c:263 generic_smp_call_function_single_interrupt+0x57/0xe6() Jul 8 12:12:12 ipam kernel: [ 68.128420] Hardware name: VMware Virtual Platform Jul 8 12:12:12 ipam kernel: [ 68.128421] Modules linked in: drbd lru_cache cn processor parport_pc parport button ac container evdev shpchp psmouse i2c_piix4 pci_hotplug i2c_core thermal_sys ehci_hcd uhci_hcd usbcore e1000 usb_common sr_mod cdrom floppy [last unloaded: scsi_wait_scan] Jul 8 12:12:12 ipam kernel: [ 68.128446] Pid: 5433, comm: migration/3 Not tainted 3.2.48-amd64 #1 Jul 8 12:12:12 ipam kernel: [ 68.128448] Call Trace: Jul 8 12:12:12 ipam kernel: [ 68.128449] <IRQ> [<ffffffff810343ad>] ? warn_slowpath_common+0x76/0x8a Jul 8 12:12:12 ipam kernel: [ 68.128458] [<ffffffff8105dd36>] ? generic_smp_call_function_single_interrupt+0x57/0xe6 Jul 8 12:12:12 ipam kernel: [ 68.128464] [<ffffffff81016790>] ? smp_call_function_single_interrupt+0x10/0x20 Jul 8 12:12:12 ipam kernel: [ 68.128469] [<ffffffff814eb5cb>] ? call_function_single_interrupt+0x6b/0x70 Jul 8 12:12:12 ipam kernel: [ 68.128470] <EOI> [<ffffffff810740f2>] ? stop_machine_cpu_stop+0x9d/0xac Jul 8 12:12:12 ipam kernel: [ 68.128475] [<ffffffff8107423c>] ? cpu_stopper_thread+0xe1/0x16e Jul 8 12:12:12 ipam kernel: [ 68.128478] [<ffffffff81074055>] ? queue_stop_cpus_work+0x91/0x91 Jul 8 12:12:12 ipam kernel: [ 68.128481] [<ffffffff810267cf>] ? mmdrop+0xd/0x1c Jul 8 12:12:12 ipam kernel: [ 68.128483] [<ffffffff810283ff>] ? finish_task_switch+0x7b/0xab Jul 8 12:12:12 ipam kernel: [ 68.128487] [<ffffffff814e2b53>] ? __schedule+0x5a7/0x5fd Jul 8 12:12:12 ipam kernel: [ 68.128490] [<ffffffff81024095>] ? __wake_up_common+0x42/0x78 Jul 8 12:12:12 ipam kernel: [ 68.128492] [<ffffffff8107415b>] ? __stop_cpus+0x5a/0x5a Jul 8 12:12:12 ipam kernel: [ 68.128496] [<ffffffff8104c8e5>] ? kthread+0x76/0x7e Jul 8 12:12:12 ipam kernel: [ 68.128499] [<ffffffff814eb9f4>] ? kernel_thread_helper+0x4/0x10 Jul 8 12:12:12 ipam kernel: [ 68.128501] [<ffffffff8104c86f>] ? flush_kthread_worker+0x8b/0x8b Jul 8 12:12:12 ipam kernel: [ 68.128503] [<ffffffff814eb9f0>] ? gs_change+0xb/0xb Jul 8 12:12:12 ipam kernel: [ 68.128505] ---[ end trace 48e668adea7dbfc4 ]--- ====================== Fernando Soto -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/