[linux-yocto] [PATCH 1/1] xilinx-zyqn: Move disable_nonboot_cpus() in front of local_irq_disable()

Mon Oct 21 20:27:00 PDT 2019

On 10/21/19 8:05 PM, Bruce Ashfield wrote:
> On Mon, Oct 21, 2019 at 6:45 AM Michal Simek <michal.simek at xilinx.com> wrote:
>> On 21. 10. 19 10:45, Quanyang Wang wrote:
>>> Hi Michal,
>>>
>>> On 10/21/19 4:16 PM, Michal Simek wrote:
>>>> On 21. 10. 19 7:50, quanyang.wang at windriver.com wrote:
>>>>> From: Quanyang Wang <quanyang.wang at windriver.com>
>>>>>
>>>>> When run kdump with enabling CONFIG_DEBUG_PREEMPT, there is a calltrace
>>>>> as below:
>>>>>
>>>>> BUG: using smp_processor_id() in preemptible [00000000] code: sh/303
>>>>> caller is machine_crash_shutdown+0x2c/0xe8
>>>>> CPU: 0 PID: 303 Comm: sh Kdump: loaded Not tainted
>>>>> 5.2.20-yocto-standard #1
>>>>> Hardware name: Xilinx Zynq Platform
>>>>> [<80112ff4>] (unwind_backtrace) from [<8010ca4c>] (show_stack+0x18/0x1c)
>>>>> [<8010ca4c>] (show_stack) from [<809b000c>] (dump_stack+0x70/0x8c)
>>>>> [<809b000c>] (dump_stack) from [<80549a14>]
>>>>> (debug_smp_processor_id+0xd4/0x118)
>>>>> [<80549a14>] (debug_smp_processor_id) from [<80111428>]
>>>>> (machine_crash_shutdown+0x2c/0xe8)
>>>>> [<80111428>] (machine_crash_shutdown) from [<801afe24>]
>>>>> (__crash_kexec+0x70/0xd0)
>>>>> [<801afe24>] (__crash_kexec) from [<801259b4>] (panic+0x110/0x324)
>>>>> [<801259b4>] (panic) from [<805f7018>] (sysrq_handle_crash+0x18/0x1c)
>>>>> [<805f7018>] (sysrq_handle_crash) from [<805f7584>]
>>>>> (__handle_sysrq+0x9c/0x14c)
>>>>> [<805f7584>] (__handle_sysrq) from [<805f79e8>]
>>>>> (write_sysrq_trigger+0x5c/0x6c)
>>>>> [<805f79e8>] (write_sysrq_trigger) from [<8031e850>]
>>>>> (proc_reg_write+0x78/0x8c)
>>>>> [<8031e850>] (proc_reg_write) from [<802b1b28>] (vfs_write+0xc0/0x154)
>>>>> [<802b1b28>] (vfs_write) from [<802b2a64>] (ksys_write+0x6c/0xd4)
>>>>> [<802b2a64>] (ksys_write) from [<80101000>] (ret_fast_syscall+0x0/0x54)
>>>>> Exception stack(0xba157fa8 to 0xba157ff0)
>>>>> 7fa0: 00000002 005ab930 00000001 005ab930 00000002 00000000
>>>>> 7fc0: 00000002 005ab930 76fa2290 00000004 76f3d124 76f3cc8c 00000000
>>>>> 00000000
>>>>> 7fe0: 00000004 7edec940 76edbfff 76e67d16
>>>>>
>>>>> This is because that the function disable_nonboot_cpus is called in
>>>>> order to make sure that the crash kernel runs in the boot CPU(cpu0).
>>>>> And it will enable local irq by calling as below:
>>>>>
>>>>> disable_nonboot_cpus
>>>>>    -> freeze_secondary_cpus
>>>>>     -> _cpu_down
>>>>>      -> percpu_down_write
>>>>>       -> rcu_sync_enter
>>>>>        -> spin_unlock_irq(&rsp->rss_lock)
>>>>>         -> local_irq_enable()
>>>>>
>>>>> Then the functions including smp_processor_id() behind
>>>>> disable_nonboot_cpus
>>>>> will run at the irq-enabled context, and this will trigger the
>>>>> calltrace.
>>>>>
>>>>> So move disable_nonboot_cpus() in front of local_irq_disable() to avoid
>>>>> it since disable_nonboot_cpus() not need run at an atomic context.
>>>>>
>>>>> Signed-off-by: Quanyang Wang <quanyang.wang at windriver.com>
>>>>> ---
>>>>>    arch/arm/kernel/machine_kexec.c | 3 ++-
>>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/arch/arm/kernel/machine_kexec.c
>>>>> b/arch/arm/kernel/machine_kexec.c
>>>>> index 654f2b1f9ac0..83d2025a4ab1 100644
>>>>> --- a/arch/arm/kernel/machine_kexec.c
>>>>> +++ b/arch/arm/kernel/machine_kexec.c
>>>>> @@ -145,9 +145,10 @@ static void machine_kexec_mask_interrupts(void)
>>>>>      void machine_crash_shutdown(struct pt_regs *regs)
>>>>>    {
>>>>> -    local_irq_disable();
>>>>>        disable_nonboot_cpus();
>>>>>    +    local_irq_disable();
>>>>> +
>>>>>        crash_smp_send_stop();
>>>>>          crash_save_cpu(regs, smp_processor_id());
>>>>>
>>>> ok. Can you please check before this if your usecases work without
>>>> disable_nonboot_cpus(). This patch was done pretty long time ago where
>>>> there was an issue with kexec. Long time ago I was talking to arm-soc
>>>> maintainers about this and they told me that mainline code should work
>>>> fine without any need to call disable_nonboot_cpus().
>>>> It means if kexec is working fine we can revert origin patch and use
>>>> what mainline is using.
>>> It seems that the issue is still there. When crash at cpu1 and crash
>>> kernel runs at cpu1,
>>>
>>> it will hang, the log is as below:
>>>
>>> root at xilinx-zynq:~# sh 1.sh
>>> syscall kexec_file_load not available.
>>> sysrq: Trigger a crash
>>> Kernel panic - not syncing: sysrq triggered crash
>>> CPU: 1 PID: 308 Comm: sh Kdump: loaded Not tainted 5.2.20-yocto-standard #4
>>> Hardware name: Xilinx Zynq Platform
>>> [<80112eb0>] (unwind_backtrace) from [<8010cc04>] (show_stack+0x18/0x1c)
>>> [<8010cc04>] (show_stack) from [<8094f8f4>] (dump_stack+0x70/0x8c)
>>> [<8094f8f4>] (dump_stack) from [<801256f4>] (panic+0xf8/0x320)
>>> [<801256f4>] (panic) from [<805dbeb0>] (sysrq_handle_crash+0x18/0x1c)
>>> [<805dbeb0>] (sysrq_handle_crash) from [<805dc3b8>]
>>> (__handle_sysrq+0x9c/0x148)
>>> [<805dc3b8>] (__handle_sysrq) from [<805dc804>]
>>> (write_sysrq_trigger+0x5c/0x6c)
>>> [<805dc804>] (write_sysrq_trigger) from [<8031b040>]
>>> (proc_reg_write+0x78/0x8c)
>>> [<8031b040>] (proc_reg_write) from [<802aeec4>] (vfs_write+0xc0/0x154)
>>> [<802aeec4>] (vfs_write) from [<802afd18>] (ksys_write+0x64/0xc8)
>>> [<802afd18>] (ksys_write) from [<80101000>] (ret_fast_syscall+0x0/0x54)
>>> Exception stack(0xb905bfa8 to 0xb905bff0)
>>> bfa0:                   00000002 0059afa0 00000001 0059afa0 00000002
>>> 00000000
>>> bfc0: 00000002 0059afa0 76f8e290 00000004 76f29124 76f28c8c 00000000
>>> 00000000
>>> bfe0: 00000004 7eb858c0 76ec7fff 76e53d16
>>> CPU 0 will stop doing anything useful since another CPU has crashed
>>> Loading crashdump kernel...
>>> Bye!
>>> Booting Linux on physical CPU 0x1
>>> Linux version 5.2.20-yocto-standard (oe-user at oe-host) (gcc version 9.2.0
>>> (GCC)) #1 SMP PREEMPT Thu Oct 17 08:15:14 UTC 2019
>>> CPU: ARMv7 Processor [413fc090] revision 0 (ARMv7), cr=18c5387d
>>> CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
>>> OF: fdt: Machine model: Xilinx ZC706 board
>>> OF: fdt: Ignoring memory range 0x0 - 0x8000000
>>> printk: debug: ignoring loglevel setting.
>>> printk: bootconsole [earlycon0] enabled
>>> Memory policy: Data cache writealloc
>>> cma: Reserved 16 MiB at 0x16c00000
>>> On node 0 totalpages: 65280
>>>    Normal zone: 574 pages used for memmap
>>>    Normal zone: 0 pages reserved
>>>    Normal zone: 65280 pages, LIFO batch:15
>>> percpu: Embedded 19 pages/cpu s47756 r8192 d21876 u77824
>>> pcpu-alloc: s47756 r8192 d21876 u77824 alloc=19*4096
>>> pcpu-alloc: [0] 0 [0] 1
>>> Built 1 zonelists, mobility grouping on.  Total pages: 64706
>>> Kernel command line: console=ttyPS0,115200n8 root=/dev/nfs rw
>>> nfsroot=128.224.165.20:/export/pxeboot/vlm-boards/22009/rootfs,v3,tcp
>>> ip=128.224.179.217:128.224.165.20:128.224.178.1:255.255.254.0:zc702:eth0:off
>>> ignore_loglevel earlyprintk noinitrd selinux=0 enforcing=0 kmemleak=on
>>> elfcorehdr=0x17f00000 mem=261120K
>>> Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
>>> Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
>>> Memory: 227332K/261120K available (9216K kernel code, 725K rwdata, 2284K
>>> rodata, 1024K init, 567K bss, 17404K reserved, 16384K cma-reserved)
>>> SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=1
>>> ftrace: allocating 35203 entries in 69 pages
>>> rcu: Preemptible hierarchical RCU implementation.
>>> rcu:    RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=2.
>>>          Tasks RCU enabled.
>>> rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies.
>>> rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=2
>>> NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
>>> efuse mapped to (ptrval)
>>> slcr mapped to (ptrval)
>>> L2C: platform provided aux values match the hardware, so have no
>>> effect.  Please remove them.
>>> L2C-310 erratum 769419 enabled
>>> L2C-310 enabling early BRESP for Cortex-A9
>>> L2C-310: enabling full line of zeros but not enabled in Cortex-A9
>>> L2C-310 ID prefetch enabled, offset 1 lines
>>> L2C-310 dynamic clock gating enabled, standby mode enabled
>>> L2C-310 cache controller enabled, 8 ways, 512 kB
>>> L2C-310: CACHE_ID 0x410000c8, AUX_CTRL 0x76760001
>>> random: get_random_bytes called from start_kernel+0x2b0/0x4c4 with
>>> crng_init=0
>>> zynq_clock_init: clkc starts at (ptrval)
>>> Zynq clock init
>>> sched_clock: 64 bits at 333MHz, resolution 3ns, wraps every 4398046511103ns
>>> clocksource: arm_global_timer: mask: 0xffffffffffffffff max_cycles:
>>> 0x4ce07af025, max_idle_ns: 440795209040 ns
>>> Switching to timer-based delay loop, resolution 3ns
>>> clocksource: ttc_clocksource: mask: 0xffff max_cycles: 0xffff,
>>> max_idle_ns: 537538477 ns
>>> timer #0 at (ptrval), irq=17
>>> Console: colour dummy device 80x30
>>> Calibrating delay loop (skipped), value calculated using timer
>>> frequency.. 666.66 BogoMIPS (lpj=3333333)
>>> pid_max: default: 32768 minimum: 301
>>> LSM: Security Framework initializing
>>> Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
>>> Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
>>> CPU: Testing write buffer coherency: ok
>>> CPU0: Spectre v2: using BPIALL workaround
>>> CPU0: thread -1, cpu 1, socket 0, mpidr 80000001
>>> Setting up static identity map for 0x8100000 - 0x8100060
>>> rcu: Hierarchical SRCU implementation.
>>> smp: Bringing up secondary CPUs ...
>> ok. Can you send content of your 1.sh script?
>>
>> Anyway the patch looks good to me.
>> Bruce: Feel free to take it. I will add it to Xilinx tree too.
> Ack'd. Will pull it into my queue.

Hi Bruce,

Would you please hang up this patch? I just sent some other patches

which conflicts with this patch.

Thanks,

Quanyang

>
> Bruce
>
>> Thanks,
>> Michal
>>
>>
>