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SubjectRe: [kcov] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1]
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On 04/20/2018 07:45 PM, Yury Norov wrote:
> On Fri, Apr 20, 2018 at 05:08:23PM +0300, Andrey Ryabinin wrote:
>>
>>
>> On 04/19/2018 06:01 AM, Fengguang Wu wrote:
>>> Hello,
>>>
>>> FYI this happens in mainline kernel 4.17.0-rc1.
>>> It at least dates back to v4.8 .
>>>
>>> [ 25.697463]
>>> [ 25.697463] Start testing find_bit() with random-filled bitmap
>>> [ 25.736615] find_next_bit: 30203201 ns, 163965 iterations
>>> [ 25.783266] find_next_zero_bit: 45554622 ns, 163716 iterations
>>> [ 25.832480] find_last_bit: 48003878 ns, 163965 iterations
>>> [ 52.050031] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:1]
>>> [ 52.050031] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.17.0-rc1 #210
>>> [ 52.050031] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
>>> [ 52.050031] RIP: 0010:__sanitizer_cov_trace_pc+0x65/0x66:
>>> __sanitizer_cov_trace_pc at kernel/kcov.c:111
>>> [ 52.050031] RSP: 0000:ffff88000fd43e40 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
>>> [ 52.050031] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000017
>>> [ 52.050031] RDX: 0000000000000000 RSI: ffff88000fd3e000 RDI: 0000000000000002
>>> [ 52.050031] RBP: 0000000000050000 R08: 0000000000000008 R09: 0000000000000000
>>> [ 52.050031] R10: ffff88000fd3e000 R11: 00000000222e2c32 R12: ffffffff85565d90
>>> [ 52.050031] R13: 0000000000030f80 R14: 0000000000030f80 R15: 0000000000000000
>>> [ 52.050031] FS: 0000000000000000(0000) GS:ffff88001f600000(0000) knlGS:0000000000000000
>>> [ 52.050031] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> [ 52.050031] CR2: 0000000000000000 CR3: 0000000003c6a000 CR4: 00000000000006b0
>>> [ 52.050031] Call Trace:
>>> [ 52.050031] find_first_bit+0x66/0x7c:
>>> find_first_bit at lib/find_bit.c:106 (discriminator 1)
>>> [ 52.050031] test_find_first_bit+0x3a/0x93
>>
>>
>> I suppose test_find_first_bit() needs a little more than zero cond_resched() calls.
>
> Or just decrease length of bitmap in this test. find_first_bit() takes
> lion's share of time of the test.
>

Yeah, that would be better.

> Start testing find_bit() with random-filled bitmap
> find_next_bit: 240043 cycles, 164062 iterations
> find_next_zero_bit: 312848 cycles, 163619 iterations
> find_last_bit: 193748 cycles, 164062 iterations
> find_first_bit: 177720874 cycles, 164062 iterations
>
> I'll test the patch and send it soon if you OK with it.
>
> Yury
>

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