Messages in this thread Patch in this message | | | Date | Sat, 17 Mar 2007 16:02:17 +0300 | From | Oleg Nesterov <> | Subject | Re: + remove-the-likelypid-check-in-copy_process.patch added to -mm tree |
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On 03/16, Eric W. Biederman wrote: > > Oleg Nesterov <oleg@tv-sign.ru> 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 <sukadev@us.ibm.com>
Explicitly set pgid and sid of init process to 1.
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Serge Hallyn <serue@us.ibm.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Herbert Poetzl <herbert@13thfloor.at> Cc: <containers@lists.osdl.org> Acked-by: Eric W. Biederman <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
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?
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