Claudio Jeker <cje...@diehard.n-r-g.com> wrote: > On Thu, Dec 16, 2021 at 03:55:43PM +0800, Vladimir Nikishkin wrote: > > Hello, everyone > > > > Recently I had a problem: my system is losing network connectivity, > > although the interface (vio0 on KVM) seemed up. Restarting the > > connection with `ifconfig vio0 down` and `ifconfig vio0 up` restores the > > connection. > > > > However, when I timed the execution, I found that the second `up` can > > take up to 15 minutes. (Hugely unexpected!) To find out where the > > program is waiting, I decided to recompile ifconfig from source with > > debugging and profiling support. > > > > Slightly adjusting the commands provided by the Makefile, I came up with > > the following commands: > > > > ``` > > egcc -O0 -g -pg -fPIC -Werror-implicit-function-declaration -c ifconfig.c > > egcc -O0 -g -pg -fPIC -Werror-implicit-function-declaration -c brconfig.c > > egcc -O0 -g -pg -fPIC -Werror-implicit-function-declaration -c sff.c > > egcc -g -pg -shared -pie -o ifconfig ifconfig.o brconfig.o sff.o -lc -pg > > ``` > > > > However, when I run ./ifconfig compiled like this, I am getting (besides > > the output of ifconfig itself) the following error message: > > > > ``` > > gmon.out: No such file or directory > > ``` > > > > I find this unexpected. Compiling and linking a simple helloworld with > > -pg -g seems to be working fine, and gmon.out is produced as expected. > > > > What am I doing wrong? Is there something specific that needs to be > > permitted to profile ifconfig? > > I doubt the problem is in ifconfig(8) itself but more an ioctl that takes > long to finish. Anyway for prfiling to work you need to neuter unveil() in > ifconfig. e.g. by changing the code. With unveil on the gmon.out file > written in the atexit handler can't be created.
Wrong tool being used to debug a userland program. It is better to attach a debugger to a -g executable. Or use ktrace -di with kdump, to figure out what system calls it is stuck in. And I suspect you will quickly decide there is no problem in ifconfig..
