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SubjectDisabling an interrupt in the handler locks the system up
Date
Hello,

On my platform, one HW block pulls the interrupt line high
as long as it remains idle, and low when it is busy.

The device tree node is:

test@22222 {
compatible = "vendor,testme";
interrupts = <23 IRQ_TYPE_LEVEL_HIGH>;
};

I wrote a minimal driver which registers the irq.
And in the interrupt handler, I disable said irq.

Since the irq is IRQ_TYPE_LEVEL_HIGH, it will fire as soon as
it is registered (because the block is idle).

Here is the code I've been running, request_irq doesn't return.

#include <linux/module.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>

static irqreturn_t test_isr(int irq, void *dev)
{
printk("irq=%d dev=%p\n", irq, dev);
disable_irq_nosync(irq);
printk("IRQ %d NOW DISABLED\n", irq);
return IRQ_HANDLED;
}

static int test_probe(struct platform_device *pdev)
{
unsigned res, virq;
printk("ENTER %s\n", __func__);

virq = irq_of_parse_and_map(pdev->dev.of_node, 0);
printk("virq = %u\n", virq);

res = request_irq(virq, test_isr, 0, "testme", (void *)0x42);
printk("request_irq = %d\n", res);

return 0;
}

static const struct of_device_id test_ids[] = {
{ .compatible = "vendor,testme" },
{ /* sentinel */ }
};

static struct platform_driver test_driver = {
.probe = test_probe,
.driver = {
.name = "test",
.of_match_table = test_ids,
},
};

module_platform_driver(test_driver);
MODULE_LICENSE("GPL");


And here's what I get when I try to load the module:
(I'm using the default CONFIG_RCU_CPU_STALL_TIMEOUT=21)

$ insmod test.ko
[ 91.571065] ENTER test_probe
[ 91.574208] virq = 21
[ 91.576902] irq=21 dev=00000042
[ 91.580061] IRQ 21 NOW DISABLED
[ 102.038544] nfs: server 172.27.64.1 not responding, still trying
[ 112.571855] INFO: rcu_preempt self-detected stall on CPU
[ 112.577201] 0-...: (6298 ticks this GP) idle=c45/140000000000002/0 softirq=1295/1295 fqs=2045
[ 112.585942] (t=6300 jiffies g=208 c=207 q=20)
[ 112.590497] Task dump for CPU 0:
[ 112.593735] insmod R running 0 951 929 0x00000002
[ 112.600124] Backtrace:
[ 112.602601] [<c010b9a4>] (dump_backtrace) from [<c010bba0>] (show_stack+0x18/0x1c)
[ 112.610207] r7:c0702434[ 112.612571] r6:c07024c8
r5:000003a1[ 112.616163] r4:df570dc0
[ 112.618701]
[ 112.620202] [<c010bb88>] (show_stack) from [<c0143a28>] (sched_show_task+0xbc/0x110)
[ 112.627989] [<c014396c>] (sched_show_task) from [<c0145ef0>] (dump_cpu_task+0x40/0x48)
[ 112.635943] r5:00000000[ 112.638307] r4:00000000
[ 112.640845]
[ 112.642347] [<c0145eb0>] (dump_cpu_task) from [<c01a8130>] (rcu_dump_cpu_stacks+0xb0/0xcc)
[ 112.650651] r5:00000000[ 112.653014] r4:c070a840
[ 112.655553]
[ 112.657055] [<c01a8080>] (rcu_dump_cpu_stacks) from [<c01743ec>] (rcu_check_callbacks+0x8f8/0x9b0)
[ 112.666058] r10:c07024c0[ 112.668509] r9:c0702518
r8:1f5a3000[ 112.672100] r7:c070a840
r6:c0702100[ 112.675691] r5:c0637f40
[ 112.678230] r4:dfbdaf40[ 112.680592] r3:ffff2458
[ 112.683130]
[ 112.684629] [<c0173af4>] (rcu_check_callbacks) from [<c0177b70>] (update_process_times+0x3c/0x64)
[ 112.693545] r10:c0188c54[ 112.695995] r9:00000001
r8:dfbd870c[ 112.699588] r7:0000001a
r6:00000000[ 112.703178] r5:df570dc0
[ 112.705717] r4:ffffe000[ 112.708080]
[ 112.709581] [<c0177b34>] (update_process_times) from [<c0188c50>] (tick_sched_handle+0x50/0x54)
[ 112.718322] r7:0000001a[ 112.720684] r6:35192494
r5:def2dab8[ 112.724274] r4:dfbd88f8
[ 112.726812]
[ 112.728309] [<c0188c00>] (tick_sched_handle) from [<c0188cb0>] (tick_sched_timer+0x5c/0xa0)
[ 112.736705] [<c0188c54>] (tick_sched_timer) from [<c0178bf4>] (__hrtimer_run_queues+0x11c/0x1ac)
[ 112.745533] r7:00000000[ 112.747896] r6:dfbd8700
r5:dfbd88f8[ 112.751486] r4:dfbd86c0
[ 112.754025]
[ 112.755519] [<c0178ad8>] (__hrtimer_run_queues) from [<c0178e88>] (hrtimer_interrupt+0xbc/0x20c)
[ 112.764347] r10:dfbd8738[ 112.766798] r9:dfbd8778
r8:dfbd8758[ 112.770389] r7:dfbd86d4
r6:ffffffff[ 112.773979] r5:00000003
[ 112.776518] r4:dfbd86c0[ 112.778881]
[ 112.780378] [<c0178dcc>] (hrtimer_interrupt) from [<c010ed0c>] (twd_handler+0x38/0x48)
[ 112.788332] r10:def2dab8[ 112.790782] r9:df402400
r8:00000001[ 112.794373] r7:df408700
r6:00000013[ 112.797964] r5:c0702744
[ 112.800504] r4:00000001[ 112.802866]
[ 112.804362] [<c010ecd4>] (twd_handler) from [<c016a134>] (handle_percpu_devid_irq+0x94/0x14c)
[ 112.812928] r5:c0702744[ 112.815291] r4:df405300
[ 112.817829]
[ 112.819327] [<c016a0a0>] (handle_percpu_devid_irq) from [<c0165134>] (generic_handle_irq+0x2c/0x3c)
[ 112.828417] r7:def2dbd0[ 112.830780] r6:00000013
r5:00000000[ 112.834370] r4:c0635ec4
[ 112.836909]
[ 112.838404] [<c0165108>] (generic_handle_irq) from [<c01656dc>] (__handle_domain_irq+0x84/0xf4)
[ 112.847150] [<c0165658>] (__handle_domain_irq) from [<c01014ac>] (gic_handle_irq+0x50/0x94)
[ 112.855541] r10:def2dbd0[ 112.857992] r9:e0803100
r8:e0802100[ 112.861583] r7:def2dab8
r6:e080210c[ 112.865173] r5:c0702744
[ 112.867712] r4:c070ff50[ 112.870076] r3:def2dab8
[ 112.872614]
[ 112.874107] [<c010145c>] (gic_handle_irq) from [<c010c70c>] (__irq_svc+0x6c/0xa8)
[ 112.881626] Exception stack(0xdef2dab8 to 0xdef2db00)
[ 112.886699] daa0: 00000000 c057c9b4
[ 112.894919] dac0: c07216c0 00000000 00000202 ffffe000 00000013 00000000 00000001 df402400
[ 112.903140] dae0: def2dbd0 def2db64 def2daf8 def2db08 c030db68 c0121068 20000113 ffffffff
[ 112.911356] r9:def2c000[ 112.913719] r8:00000001
r7:def2daec[ 112.917310] r6:ffffffff
r5:20000113[ 112.920901] r4:c0121068
[ 112.923448] [<c0120fc0>] (__do_softirq) from [<c0121520>] (irq_exit+0xd4/0x110)
[ 112.930792] r10:def2dbd0[ 112.933242] r9:df402400
r8:00000001[ 112.936833] r7:00000000
r6:00000013[ 112.940423] r5:00000000
[ 112.942962] r4:c0635ec4[ 112.945324]
[ 112.946819] [<c012144c>] (irq_exit) from [<c01656e0>] (__handle_domain_irq+0x88/0xf4)
[ 112.954690] [<c0165658>] (__handle_domain_irq) from [<c01014ac>] (gic_handle_irq+0x50/0x94)
[ 112.963080] r10:00000000[ 112.965531] r9:e0803100
r8:e0802100[ 112.969122] r7:def2dbd0
r6:e080210c[ 112.972714] r5:c0702744
[ 112.975253] r4:c070ff50[ 112.977617] r3:def2dbd0
[ 112.980154]
[ 112.981648] [<c010145c>] (gic_handle_irq) from [<c010c70c>] (__irq_svc+0x6c/0xa8)
[ 112.989166] Exception stack(0xdef2dbd0 to 0xdef2dc18)
[ 112.994240] dbc0: df506260 60000013 00000000 00000005
[ 113.002460] dbe0: dedbd680 df506200 00000015 df506260 60000013 df506238 00000000 def2dc2c
[ 113.010679] dc00: def2dc30 def2dc20 c0167f90 c04d68d0 60000013 ffffffff
[ 113.017324] r9:def2c000[ 113.019687] r8:60000013
r7:def2dc04[ 113.023277] r6:ffffffff
r5:60000013[ 113.026868] r4:c04d68d0
[ 113.029418] [<c04d68a8>] (_raw_spin_unlock_irqrestore) from [<c0167f90>] (__setup_irq+0x440/0x5f0)
[ 113.038426] [<c0167b50>] (__setup_irq) from [<c0168300>] (request_threaded_irq+0xf0/0x188)
[ 113.046730] r10:00000000[ 113.049179] r9:00000015
r8:df506210[ 113.052770] r7:00000000
r6:df506200[ 113.056362] r5:00000000
[ 113.058901] r4:dedbd680[ 113.061263]
[ 113.062767] [<c0168210>] (request_threaded_irq) from [<bf0040b8>] (test_probe+0x74/0x90 [zozo])
[ 113.071508] r10:00000000[ 113.073959] r9:21242a5c
r8:00000001[ 113.077550] r7:fffffdfb
r6:bf004320[ 113.081142] r5:df516810
[ 113.083681] r4:00000015[ 113.086044] r3:00000000
[ 113.088582]
[ 113.090085] [<bf004044>] (test_probe [zozo]) from [<c03595e8>] (platform_drv_probe+0x54/0xb8)
[ 113.098652] r4:c0752d30[ 113.101014]
[ 113.102510] [<c0359594>] (platform_drv_probe) from [<c0357b88>] (driver_probe_device+0x228/0x2b8)
[ 113.111425] r7:bf004320[ 113.113789] r6:df516844
r5:df516810[ 113.117379] r4:c0752d30
[ 113.119917]
[ 113.121412] [<c0357960>] (driver_probe_device) from [<c0357cd8>] (__driver_attach+0xc0/0xc4)
[ 113.129891] r9:21242a5c[ 113.132255] r8:00000001
r7:00000000[ 113.135845] r6:df516844
r5:bf004320[ 113.139436] r4:df516810
[ 113.141980] [<c0357c18>] (__driver_attach) from [<c0355d00>] (bus_for_each_dev+0x70/0xa4)
[ 113.150196] r7:00000000[ 113.152560] r6:c0357c18
r5:bf004320[ 113.156150] r4:00000000
[ 113.158689]
[ 113.160183] [<c0355c90>] (bus_for_each_dev) from [<c03573d4>] (driver_attach+0x24/0x28)
[ 113.168224] r6:c0714090[ 113.170587] r5:df7efc80
r4:bf004320[ 113.174178]
[ 113.175673] [<c03573b0>] (driver_attach) from [<c0356fa0>] (bus_add_driver+0x1a8/0x220)
[ 113.183719] [<c0356df8>] (bus_add_driver) from [<c0358498>] (driver_register+0x80/0x100)
[ 113.191848] r7:bf004380[ 113.194211] r6:dedbdc80
r5:bf006000[ 113.197801] r4:bf004320
[ 113.200339]
[ 113.201834] [<c0358418>] (driver_register) from [<c0359548>] (__platform_driver_register+0x48/0x50)
[ 113.210924] r5:bf006000[ 113.213287] r4:c0714090
[ 113.215826]
[ 113.217323] [<c0359500>] (__platform_driver_register) from [<bf006020>] (test_driver_init+0x20/0x24 [zozo])
[ 113.227113] r5:bf006000[ 113.229475] r4:ffffe000
[ 113.232014]
[ 113.233511] [<bf006000>] (test_driver_init [zozo]) from [<c01017f4>] (do_one_initcall+0x4c/0x17c)
[ 113.242432] [<c01017a8>] (do_one_initcall) from [<c01a81b4>] (do_init_module+0x68/0x3a4)
[ 113.250561] r10:dedbd5c8[ 113.253011] r9:21242a5c
r8:00000001[ 113.256602] r7:bf004380
r6:dedbdc80[ 113.260193] r5:00000001
[ 113.262732] r4:bf004380[ 113.265094]
[ 113.266591] [<c01a814c>] (do_init_module) from [<c01925f0>] (load_module+0x1dc0/0x2180)
[ 113.274633] r6:dedbd5c0[ 113.276997] r5:00000001
r4:def2df34[ 113.280587]
[ 113.282082] [<c0190830>] (load_module) from [<c0192b08>] (SyS_init_module+0x158/0x170)
[ 113.290037] r10:00000051[ 113.292487] r9:def2c000
r8:01bbf008[ 113.296078] r7:e08682cc
r6:00000000[ 113.299667] r5:01bc02e4
[ 113.302207] r4:000012cc[ 113.304569]
[ 113.306065] [<c01929b0>] (SyS_init_module) from [<c0107ba0>] (ret_fast_syscall+0x0/0x3c)
[ 113.314194] r10:00000000[ 113.316645] r9:def2c000
r8:c0107d64[ 113.320236] r7:00000080
r6:be98bb54[ 113.323828] r5:be98bc6d
[ 113.326368] r4:000012cc[ 113.328729]


Are we not supposed to disable the irq in the handler?

Regards.

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