[PATCH] ARM: irq_work: Do not attempt to IPI on non IPI-capable HW

Hi Marc,

On Tue, Aug 16, 2016 at 12:26 PM, Marc Zyngier [off-list ref] wrote:

Not all of the ARM HW is IPI capable (i.e. most of the non-SMP
systems). Unfortunately, some systems do advertise being SMP
capable, even if they have a single core and do not define
a cross call method. In this case, irq_work_queue dies
as arch_irq_work_has_interrupt() fails to detect this
particular case.

Let's redefine arch_irq_work_has_interrupt() to actually check
if we're IPI capable instead of simply being SMP. This sidesteps
the issue entierely.

Signed-off-by: Marc Zyngier <redacted>

With this patch applied I still get a hang after running the 'reboot'
command on a mx6ul:

Requesting system reboot
[    9.659735] ci_hdrc ci_hdrc.1: remove, state 4
[    9.665652] usb usb1: USB disconnect, device number 1
[    9.697777] ci_hdrc ci_hdrc.1: USB bus 1 deregistered
[   35.741678] INFO: rcu_sched detected stalls on CPUs/tasks:
[   35.747244]  (detected by 0, t=2602 jiffies, g=-92, c=-93, q=13)
[   35.753324] All QSes seen, last rcu_sched kthread activity 2602 (-26427--2900
[   35.764480] init            R running      0   151      1 0x00000002
[   35.770919] Backtrace:
[   35.773455] [<c010b71c>] (dump_backtrace) from [<c010b8b8>] (show_stack+0x18)
[   35.781051]  r6:c0e6e017 r5:00000001 r4:ce3c8c00 r3:00000000
[   35.786863] [<c010b8a0>] (show_stack) from [<c0150178>] (sched_show_task+0x1)
[   35.794742] [<c0150054>] (sched_show_task) from [<c018807c>] (rcu_check_call)
[   35.803378]  r6:c0d78340 r5:c0e154c0 r4:cedd1340
[   35.808120] [<c0187830>] (rcu_check_callbacks) from [<c018b0f0>] (update_pro)
[   35.817013]  r10:c0e229e8 r9:c019cbd4 r8:cedce908 r7:ce3afd98 r6:cedce908 r50
[   35.824998]  r4:ce3c8c00
[   35.827596] [<c018b0b8>] (update_process_times) from [<c019cb18>] (tick_sche)
[   35.836314]  r5:00000008 r4:51acc1a4
[   35.839977] [<c019cac8>] (tick_sched_handle) from [<c019cc34>] (tick_sched_t)
[   35.848369] [<c019cbd4>] (tick_sched_timer) from [<c018bb7c>] (__hrtimer_run)
[   35.857089]  r7:cedce640 r6:cedce5c0 r5:cedce64c r4:00000000
[   35.862897] [<c018ba94>] (__hrtimer_run_queues) from [<c018c3a8>] (hrtimer_i)
[   35.871702]  r10:cedce698 r9:cedce678 r8:cedce6b8 r7:cedce5c0 r6:cedce600 r53
[   35.879685]  r4:ffffffff
[   35.882283] [<c018c2e0>] (hrtimer_interrupt) from [<c06a6c5c>] (mxc_timer_in)
[   35.890916]  r10:c0e6e052 r9:d0805000 r8:ce81d000 r7:00000010 r6:ce3afcd4 r50
[   35.898899]  r4:ce802440
[   35.901495] [<c06a6c20>] (mxc_timer_interrupt) from [<c0179514>] (__handle_i)
[   35.910909]  r4:ce802500 r3:c06a6c20
[   35.914572] [<c01794b8>] (__handle_irq_event_percpu) from [<c0179628>] (hand)
[   35.924246]  r10:ce806000 r9:d0805000 r8:00000001 r7:00000000 r6:c0e103b8 r50
[   35.932228]  r4:ce81d000
[   35.934822] [<c0179604>] (handle_irq_event_percpu) from [<c01796a4>] (handle)
[   35.943715]  r5:ce81d060 r4:ce81d000
[   35.947382] [<c0179664>] (handle_irq_event) from [<c017cda0>] (handle_fasteo)
[   35.955929]  r6:c0e103b8 r5:ce81d060 r4:ce81d000 r3:00000000
[   35.961737] [<c017cccc>] (handle_fasteoi_irq) from [<c0178cbc>] (generic_han)
[   35.970368]  r7:00000000 r6:c0d75fa8 r5:c0e02b1c r4:00000010
[   35.976175] [<c0178c9c>] (generic_handle_irq) from [<c0178e00>] (__handle_do)
[   35.984914] [<c0178d94>] (__handle_domain_irq) from [<c01015e0>] (gic_handle)
[   35.993285]  r10:000003eb r8:c0e22c00 r7:c0e02c80 r6:ce3afd98 r5:d080400c r40
[   36.001286] [<c0101594>] (gic_handle_irq) from [<c010c4f0>] (__irq_svc+0x70/)
[   36.008796] Exception stack(0xce3afd98 to 0xce3afde0)
[   36.013877] fd80:                                                       ce311
[   36.022093] fda0: 00000000 00000003 ce313adc ce312200 c0e02a50 ce313a80 c0100
[   36.030306] fdc0: 00000000 ce3afdfc ce3afe00 ce3afde8 c066a1a8 c01b47f0 2000f
[   36.038503]  r10:00000000 r9:ce3ae000 r8:c0108084 r7:ce3afdcc r6:ffffffff r53
[   36.046488]  r4:c01b47f0 r3:ce3c8c00
[   36.050165] [<c01b47bc>] (irq_work_sync) from [<c066a1a8>] (cpufreq_dbs_gove)
[   36.058974]  r4:00000004 r3:00000001
[   36.062649] [<c066a158>] (cpufreq_dbs_governor_stop) from [<c0666d74>] (cpuf)
[   36.072149]  r7:c1658f10 r6:c0e4dd20 r5:ce3122e0 r4:ce312200
[   36.077953] [<c0666d3c>] (cpufreq_stop_governor) from [<c0666de8>] (cpufreq_)
[   36.086698] [<c0666d7c>] (cpufreq_suspend) from [<c04ea7d4>] (syscore_shutdo)
[   36.094897]  r7:00000000 r6:c0e70020 r5:c0e322f0 r4:c0e4dd44
[   36.100703] [<c04ea788>] (syscore_shutdown) from [<c0147f74>] (kernel_restar)
[   36.108814]  r6:c0e139bc r5:4321fedc r4:00000000 r3:ce834980
[   36.114613] [<c0147f58>] (kernel_restart) from [<c0148190>] (SyS_reboot+0x18)
[   36.122377]  r4:01234567 r3:01234567
[   36.126042] [<c0148004>] (SyS_reboot) from [<c0107ee0>] (ret_fast_syscall+0x)
[   36.133719]  r7:00000058 r6:000bf7d8 r5:00000000 r4:00000000
[   36.139518] rcu_sched kthread starved for 2602 jiffies! g4294967204 c42949670
[   36.149972] rcu_sched       R running      0     7      2 0x00000000
[   36.156409] Backtrace:
[   36.158923] [<c0923294>] (__schedule) from [<c0923ae4>] (schedule+0x3c/0xa0)
[   36.165997]  r10:00000000 r9:c0e02b1c r8:ffffffff r7:c0e02100 r6:ffff8e9c r58
[   36.173985]  r4:cedcd4c0
[   36.176581] [<c0923aa8>] (schedule) from [<c0928070>] (schedule_timeout+0x21)
[   36.184366] [<c0927e5c>] (schedule_timeout) from [<c0186e4c>] (rcu_gp_kthrea)
[   36.192651]  r10:00000001 r9:00000003 r8:00000000 r7:000002b8 r6:00000001 r50
[   36.200631]  r4:c0e154c0
[   36.203227] [<c0186a9c>] (rcu_gp_kthread) from [<c0145330>] (kthread+0xd8/0x)
[   36.210558]  r7:c0186a9c
[   36.213154] [<c0145258>] (kthread) from [<c0107f70>] (ret_from_fork+0x14/0x2)
[   36.220396]  r7:00000000 r6:00000000 r5:c0145258 r4:ce835000

With your previous proposal from:
http://www.spinics.net/lists/arm-kernel/msg522576.html

, the 'reboot' command works fine.

Thanks