Please see in line.
Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:
Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote:
Hi Rajaram ....
> Hi,
>
> In the init_module() of a kernel module , I inserted
>
> while(1);
Nasty experiment ;) but it's okay, even adult is allowed to get nasty
sometimes :)
<Raja> I am very much a small kid in kernel programming :) <Raja>
> and then tried to insert the module. When I insmoded the module,
> the system hung without any keyboard/ mouse responses.
>
> Why does this happen ?
> Even if the insmod() is busy in the kernel mode with while(1); , it
> should have been preempted by scheduler to run other processes..right
> ? ( as kernel 2.6 is preemptive even in kernel mode ).
First of all, I agree with Thomas...make sure you do enable
CONFIG_PREEMPT in the currently running kernel. Even 2.6 kernel are
preemptible in kernel mode, if this feature is disabled during kernel
compilation, then it will be disabled.
<Raja> Yes !, I saw that this flag is not set in the .config file. <Raja>
Second, I observe kernel/module.c (i use 2.6.11.1), specifically
sys_init_module(). You will see these lines:
/* Start the module */
if (mod->init != NULL)
ret = mod->init();
I don't see any lock-grabbing function prefixing those lines (especially
one who disables irq), so I firmly believe interrupt is still accepted
and processed as usual.
<Raja> but for me, the keyboard and mouse went off ! even the on/off button ! <Raja>
try this simple idea, inside the "while(1)", call schedule() to
voluntarily call the scheduler. And before inserting the module, run a
program/application and put it on nice level -19. Insert the module and
see if the application is stuck....(something that doesn't need
keyboard/mouse interactivity, maybe mpg123).
< Raja > I tried putting schedule() inside init_module(). Now it did not hang the system. I could proceed with other processes, but only the insmod never returned. But I did not try your suggestion of another process and nice value etc..
So in this case the init_module is run in time slices just to call schedule() again and voluntarily give up the CPU..is it ?
btw..what is mpg 123 ?
<Raja>
hope it helps.
<Raja> Thanks a lot <Raja>
regards,
Mulyadi
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