Date: Sun, 9 Jul 2023 23:36:03 +0000 From: John F Carr <jfc@mit.edu> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Current FreeBSD <freebsd-current@freebsd.org> Subject: Re: shell hung in fork system call Message-ID: <52A8F775-17D9-4240-A444-98AD5339622F@mit.edu> In-Reply-To: <ZKtB8B_Fs0GwVCcP@kib.kiev.ua> References: <909E2C96-3BFA-41AD-8EE7-0902231C2B95@mit.edu> <ZKtB8B_Fs0GwVCcP@kib.kiev.ua>
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> On Jul 9, 2023, at 19:25, Konstantin Belousov <kostikbel@gmail.com> wrote=
:
>=20
> On Sun, Jul 09, 2023 at 10:41:27PM +0000, John F Carr wrote:
>> Kernel and system at a146207d66f320ed239c1059de9df854b66b55b7 plus some =
irrelevant local changes, four 64 bit ARM processors, make.conf sets CPUTYP=
E?=3Dcortex-a57.
>>=20
>> I typed ^C while /bin/sh was starting a pipeline and my shell got hung i=
n the middle of fork().
>>=20
>>> From the terminal:
>>=20
>> # git log --oneline --|more
>> ^C^C^C
>> load: 3.26 cmd: sh 95505 [fork] 5308.67r 0.00u 0.03s 0% 2860k
>> mi_switch+0x198 sleepq_switch+0xfc sleepq_timedwait+0x40 _sleep+0x264 fo=
rk1+0x67c sys_fork+0x34 do_el0_sync+0x4c8 handle_el0_sync+0x44=20
>> load: 3.16 cmd: sh 95505 [fork] 5311.75r 0.00u 0.03s 0% 2860k
>> mi_switch+0x198 sleepq_switch+0xfc sleepq_timedwait+0x40 _sleep+0x264 fo=
rk1+0x67c sys_fork+0x34 do_el0_sync+0x4c8 handle_el0_sync+0x44=20
>>=20
>> According to ps -d on another terminal the shell has no children:
>>=20
>> PID TT STAT TIME COMMAND
>> [...]
>> 873 u0 IWs 0:00.00 `-- login [pam] (login)
>> 874 u0 I 0:00.17 `-- -sh (sh)
>> 95504 u0 I 0:00.01 `-- su -
>> 95505 u0 D+ 0:00.05 `-- -su (sh)
>> [...]
>>=20
>> Nothing on the (115200 bps serial) console. No change in system perform=
ance.
>>=20
>> The system is busy copying a large amount of data from the network to a =
ZFS pool on spinning disks. The git|more pipeline could have taken some ti=
me to get going while I/O requests worked their way through the queue. It =
would not have touched the busy pool, only the zroot pool on an SSD.
>>=20
>> Has anything changed recently that might cause this?
>=20
> There was some change around fork, but your sleep seems to be not from
> that change. Can you show the wait channel for the process? Do somethin=
g
> like
> $ ps alxww
>=20
UID PID PPID C PRI NI VSZ RSS MWCHAN STAT TT TIME COMMAND
0 95505 95504 2 20 0 13508 2876 fork D+ u0 0:00.13 -su (sh=
)
This is probably the same information displayed as [fork] in the output fro=
m ^T.
Does it correspond to the source line
pause("fork", hz / 2);
?
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