On 8/11/05, Vincenzo Mallozzi <vinjunior@xxxxxxxx> wrote:
> Hi,
> I've another problem with my kernel module.
> I want to stop the threads I'm monitoring when they are going to terminate
> their execution in order to can restore them to a previous state.
> To do this, I've substituted the function related with the sys_exit system
> call with the following one:
>
> static asmlinkage int cmc_sys_exit(int error_code)
> {
> if (current is one of the thread I'm monitoring){
> send_sig(SIGSTOP,current,1);
>
> return 0;
> }
>
>
>
> return original_sys_exit(error_code);
> }
>
> where original_sys_exit is the pointer to the original function.
>
> After the executing of this function, things seems to go well, as all threads
> stop the execution and do not terminate; but when they are resumed to a
> previous state, sometimes not all threads restart the execution (someone
> terminate) or can happen that all restart their execution from the previous
> state but when they re-terminate their execution they not stop (as in the
> first execution), they segfault and exit.
I am not very sure, but actually functions like _exit etc are declared
using the GCC attribute "noreturn". Even if you are using different
functions, there is a good chance that this attribute might be set.
>From unistd.h
extern void _exit (int __status) __attribute__ ((__noreturn__));
noreturn attribute *may* not restore the registers saved by the
calling function (as part of the optimization). This can possibly
explain the segmentation violations etc.
> What goes wrong?
>
> Thanks.
> Vincenzo Mallozzi.
>
>
>
>
>
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