Re: possible kernel bug in signal transit.

[Alex Lyashkov <shadow@psoft.net>]

В Вск, 14.03.2004, в 03:18, Andrew Morton пишет:
> Alex Lyashkov <shadow@psoft.net> wrote:
> >
> > Hello All
> > 
> > I analyze kernel vanila 2.6.4 and found one possible bug in
> > __kill_pg_info function.
> > 
> >         for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
> >                 err = group_send_sig_info(sig, info, p);
> >                 if (retval)
> >                         retval = err;
> >         }
> > but I think if (retval) is incorrect check. possible this cycle must be
> >         for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
> >                 err = group_send_sig_info(sig, info, p);
> >                 if (ret) {
> >                         retval = err;
> > 			break;
> > 		}
> >         }
> > because in original variant me assign to retval only first value from
> > ret and other be ignored if this value be 0.
> > 
> 
> No, the code's OK, albeit undesirably obscure.  It will return -ESRCH if
> none of the tasks had a matching pgrp and will return the result of the
> final non-zero-returning group_send_sig_info() if one or more of the
> group_send_sig_info() calls failed, and will return zero if all of the
> group_send_sig_info() calls returned zero.
> 
> Thanks for checking though..
No. it can`t return final non-zero-returning group_send_sig_info() if
first call group_send_sig_info return 0.
Example me have 3 groups it will return
1 - zero
2 - nonzero (example -1)
3 - nonzero (example -2)
original code will return zero.
but you say it will return last non zero - "-2" in example.
(do only first assignment after it retval is zero and no assignments
does.)
For her logic me can write.
=====
	int retval = 0;
	int err = -1;
        for_each_task_pid(pgrp, PIDTYPE_PGID, p, l, pid) {
                 err = group_send_sig_info(sig, info, p);
		if( err )
			retval = err;

         }
	return err==-1 ? -ESRCH : retval;
===
If me not enter to this cycle - retval = -ESRCH, and last non zero err
if cycle is worked or zero if all group_send_sig_info() return zero.


-- 
Alex Lyashkov <shadow@psoft.net>
PSoft