From: Oleg Nesterov <oleg@redhat.com>
To: Jiri Slaby <jslaby@suse.cz>
Cc: live-patching@vger.kernel.org, jpoimboe@redhat.com,
sjenning@redhat.com, jkosina@suse.cz, vojtech@suse.cz,
mingo@redhat.com, linux-kernel@vger.kernel.org,
Miroslav Benes <mbenes@suse.cz>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC kgr on klp 9/9] livepatch: send a fake signal to all tasks
Date: Mon, 4 May 2015 16:34:23 +0200 [thread overview]
Message-ID: <20150504143423.GA25809@redhat.com> (raw)
In-Reply-To: <1430739625-4658-9-git-send-email-jslaby@suse.cz>
Well, I can't really comment this change because I didn't see other
changes, and I do not know what klp_kgraft_task_in_progress() means...
On 05/04, Jiri Slaby wrote:
>
> Luckily we can force the task to do that by sending it a fake signal,
But note that signal_wake_up(0) won't wake the stopped/traced tasks up.
> +static void klp_kgraft_send_fake_signal(void)
> +{
> + struct task_struct *p;
> + unsigned long flags;
> +
> + read_lock(&tasklist_lock);
> + for_each_process(p) {
Only the group leader can be klp_kgraft_task_in_progress?
Looks like you need for_each_process_thread()...
> + /*
> + * send fake signal to all non-kthread processes which are still
> + * not migrated
> + */
> + if (!(p->flags & PF_KTHREAD) &&
So this can miss the execing kernel thread, I do not know if this is
correct or not. PF_KTHREAD is cleared in flush_old_exec().
> + klp_kgraft_task_in_progress(p) &&
> + lock_task_sighand(p, &flags)) {
No need for lock_task_sighand(). Just spin_lock_irq(p->sighand->siglock).
tasklist_lock + for_each_process guarantees that "p" has a valid ->sighand.
> + signal_wake_up(p, 0);
To remind, this won't wakeup a TASK_STOPPED/TRACED thread.
> void recalc_sigpending(void)
> {
> - if (!recalc_sigpending_tsk(current) && !freezing(current))
> + if (!recalc_sigpending_tsk(current) && !freezing(current) &&
> + !klp_kgraft_task_in_progress(current))
> clear_thread_flag(TIF_SIGPENDING);
It is not clear from this patch when TIF_SIGPENDING will be cleared.
I assume other changes add some hooks into do_notify_resume/get_signal
paths, otherwise a klp_kgraft_task_in_progress() will spin until
klp_kgraft_task_in_progress(current) becomes "false".
Oleg.
next prev parent reply other threads:[~2015-05-04 14:34 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-04 11:40 [RFC kgr on klp 1/9] livepatch: make kobject in klp_object statically allocated Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 2/9] livepatch: introduce patch/func-walking helpers Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 3/9] livepatch: add klp_*_to_patch helpers Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 4/9] livepatch: add kgr infrastructure Jiri Slaby
2015-05-04 12:23 ` Martin Schwidefsky
2015-05-05 13:27 ` Jiri Slaby
2015-05-05 14:34 ` Martin Schwidefsky
2015-05-04 11:40 ` [RFC kgr on klp 5/9] livepatch: teach klp about consistency models Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 6/9] livepatch: do not allow failure while really patching Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 7/9] livepatch: propagate the patch status to functions Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 8/9] livepatch: add kgraft-like patching Jiri Slaby
2015-05-04 11:40 ` [RFC kgr on klp 9/9] livepatch: send a fake signal to all tasks Jiri Slaby
2015-05-04 14:34 ` Oleg Nesterov [this message]
2015-05-06 12:58 ` Miroslav Benes
2015-05-04 12:20 ` [RFC kgr on klp 0/9] kGraft on the top of KLP Jiri Slaby
2015-05-04 15:44 ` Josh Poimboeuf
2015-05-04 22:48 ` Jiri Kosina
2015-05-05 3:43 ` Josh Poimboeuf
2015-05-05 6:14 ` Jiri Kosina
2015-05-05 16:24 ` Josh Poimboeuf
2015-05-12 9:45 ` Jiri Kosina
2015-05-12 15:20 ` Josh Poimboeuf
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