Hi all,
I am trying to modify the scheduler to take off some processes (such as those
generated by a forkbomb ... malicious) off the run queue. I have been looking
into the scheduler and proc.h and see there is one way by putting threads on
the 'suspension' queue. I am not sure if this is the same thing. But anyway, I
modified sched_cpu in sched_4bsd.c to look something like this:
FOREACH_THREAD_IN_PROC(p, td)
{
if(p->p_km_switch == P_NON_RUN)
{
if( !TD_IS_SUSPENDED(td) )
{
//thread_suspend_one(td);
printf("suspending thread associated with %s\n",
td->td_ksegrp->kg_proc->p_comm);
TD_SET_SUSPENDED(td);
}
}
else if(p->p_km_switch == P_RUN)
{
if(TD_IS_SUSPENDED(td))
{
//thread_unsuspend_one(td);
printf("clearing suspending thread associated with
%s\n", td->td_ksegrp->kg_proc->p_comm);
TD_CLR_SUSPENDED(td);
}
}
}
the p_km_switch turns on when a process exceeds a certain threshold of memory
usage and context switching. If the threads associated with this process are
suspended, and the system becomes less loady, then they are unsuspended (The
P_RUN flag is set externally). So I tried this out, and it seems to sort of
work although when I print out the p->p_suspcount, it says its 0, so I am not
sure if this is even working right.
Im sure you guys know the scheduler much better than I do. What would be the
best way to modify the scheduler so that given a certain NON_RUN flag I can
pretty much take a process of the run queue and then later put it back on when
the system is less loaded?
Thanks a lot,
Ash
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