On 03/16, Eric W. Biederman wrote: > > Oleg Nesterov <[EMAIL PROTECTED]> writes: > > > Sukadev Bhattiprolu wrote: > > > > This means that idle threads (except "swapper") are visible to > > for_each_process() > > and do_each_thread(). Looks dangerous and somewhat strange to me. > > > > Could you explain this change? > > Good catch. I've been so busy pounding reviewing this patches into > something that made sense that I missed the fact that we care about > this for more than just the NULL pointer that would occur if we didn't > do this.
Why it is bad to have a NULL pointer for idle thread? (Sorry for stupid question, I can't track the code changes these days). > Still it would be good if we could find a way to remove this rare > special case. > > Any chance we can undo what we don't want done for_idle, or create > a factor of copy_process that only does as much as fork_idle should do, > and make copy_process a wrapper that does the rest. > > I doubt it is significant anywhere but it would be nice to remove a > branch that except at boot up never happens. ... or at cpu-hotplug. Probably you are right, but I am not sure. The "if (p->pid)" check in essence implements CLONE_UNHASHED flag, it may be useful. Btw. Looking at http://marc.theaimsgroup.com/?l=linux-mm-commits, Subject: Explicitly set pgid and sid of init process From: Sukadev Bhattiprolu <[EMAIL PROTECTED]> Explicitly set pgid and sid of init process to 1. Signed-off-by: Sukadev Bhattiprolu <[EMAIL PROTECTED]> Cc: Cedric Le Goater <[EMAIL PROTECTED]> Cc: Dave Hansen <[EMAIL PROTECTED]> Cc: Serge Hallyn <[EMAIL PROTECTED]> Cc: Eric Biederman <[EMAIL PROTECTED]> Cc: Herbert Poetzl <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Acked-by: Eric W. Biederman <[EMAIL PROTECTED]> Signed-off-by: Andrew Morton <[EMAIL PROTECTED]> --- init/main.c | 1 + 1 file changed, 1 insertion(+) diff -puN init/main.c~explicitly-set-pgid-and-sid-of-init-process init/main.c --- a/init/main.c~explicitly-set-pgid-and-sid-of-init-process +++ a/init/main.c @@ -783,6 +783,7 @@ static int __init init(void * unused) */ init_pid_ns.child_reaper = current; + __set_special_pids(1, 1); cad_pid = task_pid(current); smp_prepare_cpus(max_cpus); Nice changelog :) The patch looks good, except __set_special_pids(1, 1) should be no-op. This is a child forked by swapper. copy_process() was changed by use-task_pgrp-task_session-in-copy_process.patch , but signal->{pgrp,_session} get its value from INIT_SIGNALS ? Could you explain this as well? Some other changes I missed? Oleg. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
