From: Oleg Nesterov <oleg@redhat.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: arjan@infradead.org, jeremy@goop.org, mschmidt@redhat.com,
mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org,
tj@kernel.org, tglx@linutronix.de,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-tip-commits@vger.kernel.org
Subject: Re: [PATCH] kthreads: Fix startup synchronization boot crash
Date: Tue, 1 Sep 2009 18:00:44 +0200 [thread overview]
Message-ID: <20090901160043.GA6708@redhat.com> (raw)
In-Reply-To: <20090901155427.GA18078@elte.hu>
On 09/01, Ingo Molnar wrote:
>
> * Oleg Nesterov <oleg@redhat.com> wrote:
>
> > But I must admit, now I don't understand what happens,
> >
> > The modification of that variable is protected by the BKL, but
> > the _ordering_ of the initial task (which becomes the idle
> > thread of CPU0) and the init task (which is spawned by the
> > initial task) is not synchronized.
> >
> > So we can occasionally end up init running sooner than
> > rest_init()
> >
> > How? rest_init() can't be preempted and it holds BKL. And
> > kernel_init() takes BKL before anything else. Confused...
>
> it cannot be preempted but it can schedule anywhere - and the BKL
> will be dropped silently.
>
> This is one of the biggest dangers of the BKL
Yes I see. But rest_init() runs under preempt_disable(). If it was
rescheduled, schedule_debug() should complain. No?
Oleg.
next prev parent reply other threads:[~2009-09-01 16:06 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-29 16:27 [PATCH] x86: detect stack protector for i386 builds on x86_64 Michal Schmidt
2009-08-30 13:39 ` Américo Wang
2009-08-30 18:43 ` [tip:x86/asm] x86: Detect " tip-bot for Michal Schmidt
2009-09-01 10:03 ` Ingo Molnar
2009-09-01 11:39 ` [PATCH] kthreads: Fix startup synchronization boot crash Ingo Molnar
2009-09-01 13:04 ` Oleg Nesterov
2009-09-01 13:14 ` Ingo Molnar
2009-09-01 13:37 ` Oleg Nesterov
2009-09-01 13:59 ` Ingo Molnar
2009-09-01 14:55 ` Oleg Nesterov
2009-09-01 15:54 ` Ingo Molnar
2009-09-01 16:00 ` Oleg Nesterov [this message]
2009-09-02 13:06 ` Ingo Molnar
2009-09-01 16:52 ` [PATCH 0/1] kthreads: simplify !kthreadd_task logic, kill kthreadd_task_init_done Oleg Nesterov
2009-09-01 16:53 ` [PATCH 1/1] " Oleg Nesterov
2009-09-01 23:22 ` [PATCH 0/1] " Eric W. Biederman
2009-09-02 9:13 ` Oleg Nesterov
2009-09-04 7:37 ` Ingo Molnar
2009-09-18 16:32 ` Wu Fei
2009-09-18 18:54 ` Oleg Nesterov
2009-09-18 19:17 ` Linus Torvalds
2009-09-18 21:12 ` Oleg Nesterov
2009-09-18 21:15 ` Oleg Nesterov
2009-09-18 22:06 ` Linus Torvalds
2009-09-18 23:11 ` Eric W. Biederman
2009-09-18 23:22 ` Oleg Nesterov
2009-09-18 23:38 ` Linus Torvalds
2009-09-01 15:08 ` [PATCH] kthreads: Fix startup synchronization boot crash Américo Wang
2009-09-01 15:19 ` Oleg Nesterov
2009-08-31 6:21 ` [PATCH] x86: detect stack protector for i386 builds on x86_64 Tejun Heo
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