Date: Mon, 10 Jul 2023 02:25:36 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: John F Carr <jfc@mit.edu> Cc: Current FreeBSD <freebsd-current@freebsd.org> Subject: Re: shell hung in fork system call Message-ID: <ZKtB8B_Fs0GwVCcP@kib.kiev.ua> In-Reply-To: <909E2C96-3BFA-41AD-8EE7-0902231C2B95@mit.edu> References: <909E2C96-3BFA-41AD-8EE7-0902231C2B95@mit.edu>
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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 CPUTYPE?=cortex-a57. > > I typed ^C while /bin/sh was starting a pipeline and my shell got hung in the middle of fork(). > > >From the terminal: > > # 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 fork1+0x67c sys_fork+0x34 do_el0_sync+0x4c8 handle_el0_sync+0x44 > 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 fork1+0x67c sys_fork+0x34 do_el0_sync+0x4c8 handle_el0_sync+0x44 > > According to ps -d on another terminal the shell has no children: > > 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) > [...] > > Nothing on the (115200 bps serial) console. No change in system performance. > > 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 time 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. > > Has anything changed recently that might cause this? 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 something like $ ps alxww
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