Hi, Off late we are seeing cpu stalls messages while mpt3sas driver unbind on powerpc machine for both mainline and linux-next kernels Machine Type: Power 8 Bare-metal Kernel version: 4.15.0-rc2 config: attached. test: driver unbind $ echo -n 0001:03:00.0 > /sys/bus/pci/drivers/mpt3sas/unbind mpt3sas_cm0: removing handle(0x000a), sas_addr(0x500304801f080d00) mpt3sas_cm0: removing : enclosure logical id(0x500304801f080d3f), slot(0) mpt3sas_cm0: removing enclosure level(0x0000), connector name( ) mpt3sas_cm0: removing handle(0x000b), sas_addr(0x500304801f080d01) mpt3sas_cm0: removing : enclosure logical id(0x500304801f080d3f), slot(1) mpt3sas_cm0: removing enclosure level(0x0000), connector name( ) mpt3sas_cm0: removing handle(0x000c), sas_addr(0x500304801f080d02) mpt3sas_cm0: removing : enclosure logical id(0x500304801f080d3f), slot(2) mpt3sas_cm0: removing enclosure level(0x0000), connector name( ) mpt3sas_cm0: removing handle(0x000d), sas_addr(0x500304801f080d03) mpt3sas_cm0: removing : enclosure logical id(0x500304801f080d3f), slot(3) mpt3sas_cm0: removing enclosure level(0x0000), connector name( ) mpt3sas_cm0: removing handle(0x000e), sas_addr(0x500304801f080d04) mpt3sas_cm0: removing : enclosure logical id(0x500304801f080d3f), slot(4) mpt3sas_cm0: removing enclosure level(0x0000), connector name( ) mpt3sas_cm0: removing handle(0x000f), sas_addr(0x500304801f080d3d) mpt3sas_cm0: removing : enclosure logical id(0x500304801f080d3f), slot(12) mpt3sas_cm0: removing enclosure level(0x0000), connector name( ) sd 16:0:0:0: [sdb] Synchronizing SCSI cache sd 16:0:0:0: [sdb] Synchronize Cache(10) failed: Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 16:0:1:0: [sdc] tag#0 FAILED Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 16:0:1:0: [sdc] tag#0 CDB: ATA command pass through(16) 85 06 2c 00 00 00 00 00 00 00 00 00 00 00 e5 00 sd 16:0:2:0: [sdd] tag#0 FAILED Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 16:0:2:0: [sdd] tag#0 CDB: ATA command pass through(16) 85 06 2c 00 00 00 00 00 00 00 00 00 00 00 e5 00 sd 16:0:3:0: [sde] tag#0 FAILED Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 16:0:3:0: [sde] tag#0 CDB: ATA command pass through(16) 85 06 2c 00 00 00 00 00 00 00 00 00 00 00 e5 00 sd 16:0:4:0: [sdf] tag#0 FAILED Result: hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK sd 16:0:4:0: [sdf] tag#0 CDB: ATA command pass through(16) 85 06 2c 00 00 00 00 00 00 00 00 00 00 00 e5 00 few minutes after above command was executed, machine is flooded with rcu stalls messages. INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 86-... } 44191221 jiffies s: 3445 root: 0x20/. blocking rcu_node structures: l=1:80-95:0x40/. Task dump for CPU 86: sh R running task 10384 18136 1 0x00042086 Call Trace: [c000007792d47370] [c000007933667200] 0xc000007933667200 (unreliable) INFO: rcu_sched self-detected stall on CPU 86-....: (50420459 ticks this GP) idle=0ae/140000000000001/0 softirq=11962/11962 fqs=24724293 (t=50420460 jiffies g=80217 c=80216 q=36817447) NMI backtrace for cpu 86 CPU: 86 PID: 18136 Comm: sh Not tainted 4.15.0-rc2-autotest #1 Call Trace: [c000007792d46f20] [c00000000099b83c] dump_stack+0xb0/0xf4 (unreliable) [c000007792d46f60] [c0000000009a43e4] nmi_cpu_backtrace+0x1a4/0x210 [c000007792d46ff0] [c0000000009a462c] nmi_trigger_cpumask_backtrace+0x1dc/0x220 [c000007792d47090] [c00000000002c7d0] arch_trigger_cpumask_backtrace+0x20/0x40 [c000007792d470b0] [c00000000017496c] rcu_dump_cpu_stacks+0xf4/0x158 [c000007792d47100] [c000000000173cb0] rcu_check_callbacks+0x8f0/0xb00 [c000007792d47230] [c00000000017c25c] update_process_times+0x3c/0x90 [c000007792d47260] [c0000000001921e4] tick_sched_handle.isra.13+0x44/0x80 [c000007792d47280] [c000000000192278] tick_sched_timer+0x58/0xb0 [c000007792d472c0] [c00000000017cd58] __hrtimer_run_queues+0xf8/0x330 [c000007792d47340] [c00000000017da74] hrtimer_interrupt+0xe4/0x280 [c000007792d47400] [c000000000022660] __timer_interrupt+0x90/0x270 [c000007792d47450] [c000000000022d30] timer_interrupt+0xa0/0xe0 [c000007792d47480] [c000000000009238] decrementer_common+0x158/0x160 --- interrupt: 901 at replay_interrupt_return+0x0/0x4 LR = arch_local_irq_restore+0x74/0x90 [c000007792d47770] [c000003fb3185000] 0xc000003fb3185000 (unreliable) [c000007792d47790] [c0000000009bb658] _raw_spin_unlock_irqrestore+0x38/0x60 [c000007792d477b0] [c00000000066f274] scsi_remove_target+0x204/0x270 [c000007792d47820] [d00000000fc72604] sas_rphy_remove+0x94/0xa0 [scsi_transport_sas] [c000007792d47850] [d00000000fc745bc] sas_port_delete+0x4c/0x238 [scsi_transport_sas] [c000007792d478b0] [d000000010e82990] mpt3sas_transport_port_remove+0x2d0/0x310 [mpt3sas] [c000007792d47950] [d000000010e71ba0] _scsih_remove_device+0x100/0x2a0 [mpt3sas] [c000007792d47a10] [d000000010e774d4] mpt3sas_device_remove_by_sas_address.part.44+0xb4/0x160 [mpt3sas] [c000007792d47a70] [d000000010e77614] _scsih_expander_node_remove+0x94/0x170 [mpt3sas] [c000007792d47af0] [d000000010e77a88] mpt3sas_expander_remove.part.46+0x398/0xe70 [mpt3sas] [c000007792d47b90] [c00000000056a9c4] pci_device_remove+0x64/0x110 [c000007792d47bd0] [c00000000060fa74] device_release_driver_internal+0x1e4/0x2c0 [c000007792d47c20] [c00000000060d260] unbind_store+0x110/0x140 [c000007792d47c70] [c00000000060c2fc] drv_attr_store+0x3c/0x60 [c000007792d47c90] [c0000000003a03c4] sysfs_kf_write+0x64/0xa0 [c000007792d47cb0] [c00000000039f1b0] kernfs_fop_write+0x170/0x250 [c000007792d47d00] [c0000000002fd370] __vfs_write+0x40/0x200 [c000007792d47d90] [c0000000002fd748] vfs_write+0xc8/0x240 [c000007792d47de0] [c0000000002fda80] SyS_write+0x60/0x110 [c000007792d47e30] [c00000000000b8e0] system_call+0x58/0x6c -- Regard's Abdul Haleem IBM Linux Technology Centre