linux-kernel - Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic

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Message-ID: <b1d41989-7f4f-eb1d-db35-07a6f6b7a7f5@linux.ibm.com>
Date:   Mon, 26 Sep 2022 10:06:58 +0200
From:   Christian Borntraeger <borntraeger@...ux.ibm.com>
To:     peterz@...radead.org
Cc:     bigeasy@...utronix.de, dietmar.eggemann@....com,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, mgorman@...e.de, mingo@...nel.org,
        oleg@...hat.com, rjw@...ysocki.net, rostedt@...dmis.org,
        tj@...nel.org, vincent.guittot@...aro.org, will@...nel.org,
        Marc Hartmayer <mhartmay@...ux.ibm.com>
Subject: Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic



Am 23.09.22 um 09:53 schrieb Christian Borntraeger:
> Am 23.09.22 um 09:21 schrieb Christian Borntraeger:
>> Peter,
>>
>> as a heads-up. This commit (bisected and verified) triggers a
>> regression in our KVM on s390x CI. The symptom is that a specific
>> testcase (start a guest with next kernel and a poky ramdisk,
>> then ssh via vsock into the guest and run the reboot command) now
>> takes much longer (300 instead of 20 seconds). From a first look
>> it seems that the sshd takes very long to end during shutdown
>> but I have not looked into that yet.
>> Any quick idea?
>>
>> Christian
> 
> the sshd seems to hang in virtio-serial (not vsock).

FWIW, sshd does not seem to hang, instead it seems to busy loop in
wait_port_writable calling into the scheduler over and over again.


> 
> PID: 237      TASK: 81d1a100          CPU: 1    COMMAND: "sshd"
>   LOWCORE INFO:
>    -psw      : 0x0404e00180000000 0x0000000131ceb136
>    -function : __list_add_valid at 131ceb136
>    -prefix   : 0x00410000
>    -cpu timer: 0x7fffffd3ec4f33d4
>    -clock cmp: 0x2639f08006283e00
>    -general registers:
>       0x00000008dcea2dce 0x00000001387d44b8
>       0x0000000081d1a228 0x00000001387d44b8
>       0x00000001387d44b8 0x00000001387d44b8
>       0x00000001387d3800 0x00000001387d3700
>       0x0000000081d1a100 0x00000001387d44b8
>       0x00000001387d44b8 0x0000000081d1a228
>       0x0000000081d1a100 0x0000000081d1a100
>       0x0000000131608b32 0x00000380004b7aa8
>    -access registers:
>       0x000003ff 0x8fff5870 0000000000 0000000000
>       0000000000 0000000000 0000000000 0000000000
>       0000000000 0000000000 0000000000 0000000000
>       0000000000 0000000000 0000000000 0000000000
>    -control registers:
>       0x00a0000014966a10 0x0000000133348007
>       0x00000000028c6140 000000000000000000
>       0x000000000000ffff 0x00000000028c6140
>       0x0000000033000000 0x0000000081f001c7
>       0x0000000000008000 000000000000000000
>       000000000000000000 000000000000000000
>       000000000000000000 0x0000000133348007
>       0x00000000db000000 0x00000000028c6000
>    -floating point registers:
>       0x000003ffb82a9761 0x0000006400000000
>       0x000003ffb82a345c 000000000000000000
>       0x0000000000007fff 0x000003ffe22fe000
>       000000000000000000 0x000003ffe22fa51c
>       0x000003ffb81889c0 000000000000000000
>       0x000002aa3ce2b470 000000000000000000
>       000000000000000000 000000000000000000
>       000000000000000000 000000000000000000
> 
>   #0 [380004b7b00] pick_next_task at 1315f2088
>   #1 [380004b7b98] __schedule at 13215e954
>   #2 [380004b7c08] schedule at 13215eeea
>   #3 [380004b7c38] wait_port_writable at 3ff80149b2e [virtio_console]
>   #4 [380004b7cc0] port_fops_write at 3ff8014a282 [virtio_console]
>   #5 [380004b7d40] vfs_write at 131889e3c
>   #6 [380004b7e00] ksys_write at 13188a2e8
>   #7 [380004b7e50] __do_syscall at 13215761c
>   #8 [380004b7e98] system_call at 132166332
>   PSW:  0705000180000000 000003ff8f8f3a2a (user space)
>   GPRS: 0000000000000015 000003ff00000000 ffffffffffffffda 000002aa02fc68a0
>         0000000000000015 0000000000000015 0000000000000000 000002aa02fc68a0
>         0000000000000004 000003ff8f8f3a08 0000000000000015 0000000000000000
>         000003ff8ffa9f58 0000000000000000 000002aa02365b20 000003ffdf4798d0