From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Ingo Molnar <mingo@kernel.org>, <akpm@linux-foundation.org>
Cc: <krinkin.m.u@gmail.com>, <mingo@elte.hu>, <peterz@infradead.org>,
<mm-commits@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: + kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch added to -mm tree
Date: Wed, 3 Feb 2016 12:42:23 +0300 [thread overview]
Message-ID: <56B1CB7F.5070207@virtuozzo.com> (raw)
In-Reply-To: <20160203074430.GA32652@gmail.com>
On 02/03/2016 10:44 AM, Ingo Molnar wrote:
> Yuck, I don't really like this.
>
> Lockdep initialization must happen early on, and it should happen in a well
> defined place, not be opportunistic (and relatively random) like this, making it
> dependent on config options and calling contexts.
>
> Also, in addition to properly ordering UBSAN initialization, how about fixing the
> silent crash by adding a lockdep warning to that place instead of an auto-init?
>
> The warning will turn lockdep off safely and will generate an actionable kernel
> message and stackdump upon which the init ordering fix can be done.
>
Something like this already done for DEBUG_LOCKDEP=y (except it initializes lockdep instead of turning it off).
look_up_lock_class():
...
#ifdef CONFIG_DEBUG_LOCKDEP
/*
* If the architecture calls into lockdep before initializing
* the hashes then we'll warn about it later. (we cannot printk
* right now)
*/
if (unlikely(!lockdep_initialized)) {
lockdep_init();
lockdep_init_error = 1;
lock_init_error = lock->name;
save_stack_trace(&lockdep_init_trace);
}
#endif
Silent crash happens only in DEBUG_LOCKDEP=n && LOCKDEP=y combination.
So, what about simply removing this #ifdef (and the other one in lockdep_info() )?
I
next prev parent reply other threads:[~2016-02-03 9:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <56b11d2d.vVw1kB2la7Y+70xF%akpm@linux-foundation.org>
2016-02-03 7:44 ` + kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch added to -mm tree Ingo Molnar
2016-02-03 9:42 ` Andrey Ryabinin [this message]
2016-02-03 9:49 ` Ingo Molnar
2016-02-03 16:51 ` Andrew Morton
2016-02-03 20:40 ` Andrew Morton
2016-02-03 21:44 ` Andrew Morton
2016-02-04 13:13 ` Andrey Ryabinin
2016-02-08 9:33 ` Michael Ellerman
2016-02-09 11:00 ` Ingo Molnar
2016-02-09 11:12 ` Ingo Molnar
2016-02-09 20:17 ` Andrew Morton
2016-02-29 9:11 ` Ingo Molnar
2016-02-29 9:25 ` Ingo Molnar
2016-02-29 9:30 ` Andrey Ryabinin
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