[Buildroot] Init not handling signals

[Buildroot] Init not handling signals

[John OSullivan]

Hi,

I'm not sure if this is the correct forum to ask this question but I have
seen a few buildroot/busybox references to this problem but none with a
clear solution.

I am running buildroot-2012-05 with busybox 1.19, using the busybox init
with an inittab based on the default one provided.

In the init tab there is a trap for ctrlaltdel

::ctrlaltdel:/sbin/reboot

 

This line is never called after hitting ctrl alt del on a keyboard

Instead we get a signal pending on the init task

Cat /proc/1/status

---------------------------

Name:   swapper

State:    R (running)

Tgid:      1

Pid:        1

PPid:      0

TracerPid:            0

Uid:        0             0             0             0

Gid:        0             0             0             0

FDSize:  32

Groups: 

Threads:              1

SigQ:      1/938

SigPnd:  0000000000000100

ShdPnd: 0000000000000002

SigBlk:   0000000000000000

SigIgn:   0000000000000000

SigCgt:  0000000000000000

CapInh: 0000000000000000

 

After the init process is signalled the Swapper task assumes 100% processor
occupancy and system performance degenerates. (as evidenced by top)

The kernel version is 2.6.33.3 (I also tried 2.6.39.4). This happens on a
minimal system built from buildroot without any other processes running, the
only way to recover the situation is with a reboot.

Any ideas or suggestions on what the issue might be?

I was going to try a non-busybox init but before I do that I want to make
sure that there is not an available explanation for the behaviour I am
observing.

 

Regards

johnos

 

 

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[Buildroot] Init not handling signals

[Thomas De Schampheleire]

John OSullivan <john.osullivan@cloudiumsystems.com> wrote:
>Hi,
>
>I'm not sure if this is the correct forum to ask this question but I have
>seen a few buildroot/busybox references to this problem but none with a
>clear solution.
>
>I am running buildroot-2012-05 with busybox 1.19, using the busybox init
>with an inittab based on the default one provided.
>
>In the init tab there is a trap for ctrlaltdel
>
>::ctrlaltdel:/sbin/reboot
>
> 
>
>This line is never called after hitting ctrl alt del on a keyboard
>
>Instead we get a signal pending on the init task
>
>Cat /proc/1/status
>
>---------------------------
>
>Name:   swapper
>
>State:    R (running)
>
>Tgid:      1
>
>Pid:        1
>
>PPid:      0
>
>TracerPid:            0
>
>Uid:        0             0             0             0
>
>Gid:        0             0             0             0
>
>FDSize:  32
>
>Groups: 
>
>Threads:              1
>
>SigQ:      1/938
>
>SigPnd:  0000000000000100
>
>ShdPnd: 0000000000000002
>
>SigBlk:   0000000000000000
>
>SigIgn:   0000000000000000
>
>SigCgt:  0000000000000000
>
>CapInh: 0000000000000000
>
> 
>
>After the init process is signalled the Swapper task assumes 100% processor
>occupancy and system performance degenerates. (as evidenced by top)
>
>The kernel version is 2.6.33.3 (I also tried 2.6.39.4). This happens on a
>minimal system built from buildroot without any other processes running, the
>only way to recover the situation is with a reboot.
>
>Any ideas or suggestions on what the issue might be?
>
>I was going to try a non-busybox init but before I do that I want to make
>sure that there is not an available explanation for the behaviour I am
>observing.
>

At first sight, I think the busybox mailing list is more appropriate... As far as I know, buildroot doesn't do anything special in this regard.

Best regards 
Thomas

[Buildroot] Init not handling signals

[Arnout Vandecappelle]

On 12/11/13 17:27, John OSullivan wrote:
> Hi,
>
> I?m not sure if this is the correct forum to ask this question but I have
> seen a few buildroot/busybox references to this problem but none with a
> clear solution.

  The busybox mailing list would probably be more appropriate...

>
> I am running buildroot-2012-05 with busybox 1.19, using the busybox init
> with an inittab based on the default one provided.
>
> In the init tab there is a trap for ctrlaltdel
>
> ::ctrlaltdel:/sbin/reboot
>
> This line is never called after hitting ctrl alt del on a keyboard
>
> Instead we get a signal pending on the init task
>
> Cat /proc/1/status
>
> ---------------------------
>
> Name:   swapper
>
> State:    R (running)
>
> Tgid:      1
>
> Pid:        1
>
> PPid:      0
>
> TracerPid:            0
>
> Uid:        0             0             0             0
>
> Gid:        0             0             0             0
>
> FDSize:  32
>
> Groups:
>
> Threads:              1
>
> SigQ:      1/938
>
> SigPnd:  0000000000000100
>
> ShdPnd: 0000000000000002

  If I understand correctly, this is a SIGCHLD and a SIGINT. The SIGINT 
is sent to init by the kernel when you press ctrlaltdel - so I guess you 
pressed it twice.

>
> SigBlk:   0000000000000000
>
> SigIgn:   0000000000000000
>
> SigCgt:  0000000000000000
>
> CapInh: 0000000000000000
>
> After the init process is signalled the Swapper task assumes 100%
> processor occupancy and system performance degenerates. (as evidenced by top)

  That seems to indicate it's getting fork-bombed. You can check that by 
running ps; ps from the shell - if the two instances have very different 
PIDs, then you have a fork bomb :-)


  Regards,
  Arnout

>
> The kernel version is 2.6.33.3 (I also tried 2.6.39.4). This happens on a
> minimal system built from buildroot without any other processes running,
> the only way to recover the situation is with a reboot.
>
> Any ideas or suggestions on what the issue might be?
>
> I was going to try a non-busybox init but before I do that I want to make
> sure that there is not an available explanation for the behaviour I am
> observing.
>
> Regards
>
> johnos
>
>
>
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot
>


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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