Re: linux-user emulation hangs during fork

[Richard Henderson <richard.henderson@linaro.org>]

On 6/5/24 02:14, Andreas Schwab wrote:
> $ qemu-x86_64 --version
> qemu-x86_64 version 9.0.50 (v9.0.0-1211-gd16cab541a)
> Copyright (c) 2003-2024 Fabrice Bellard and the QEMU Project developers
> $ cat fork.rb
> begin
>    r, w = IO.pipe
>    if pid1 = fork
>      w.close
>      r.read 1
>      Process.kill "USR1", pid1
>      Process.wait2 pid1
>    else
>      print "child\n"
>      r.close
>      if pid2 = fork
>        trap("USR1") { print "child: kill\n"; Process.kill "USR2", pid2 }
>        w.close
>        print "child: wait\n"
>        Process.wait2 pid2
>      else
>        print "grandchild\n"
>        w.close
>        sleep 0.2
>      end
>    end
> end
> $ ruby fork.rb
> child
> child: wait
> grandchild
> child: kill
> $ qemu-x86_64 /usr/bin/ruby fork.rb
> child
> child: wait
> ^Z
> [1]+  Stopped                 qemu-x86_64 /usr/bin/ruby fork.rb
> $ grep SigB $(for p in $(pidof qemu-x86_64); do echo /proc/$p/status; done | sort)
> /proc/3221/status:SigBlk:       0000000000000000
> /proc/3224/status:SigBlk:       0000000000000000
> /proc/3228/status:SigBlk:       fffffff27ffbfa9f
> 

Works for me:

rth@stoup:~/zz$ ~/qemu/bld/qemu-x86_64 `which ruby` fork.rb
child
grandchild
child: wait
child: kill
rth@stoup:~/zz$ ~/qemu/bld/qemu-x86_64 `which ruby` fork.rb
child
grandchild
child: wait
child: kill
rth@stoup:~/zz$ ~/qemu/bld/qemu-x86_64 `which ruby` fork.rb
child
grandchild
child: wait
child: kill
rth@stoup:~/zz$ ~/qemu/bld/qemu-x86_64 `which ruby` fork.rb
child
grandchild
child: wait
child: kill


r~