From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
To: lkp@lists.01.org
Subject: Re: [percpu] BUG: unable to handle kernel NULL pointer dereference at (null)
Date: Tue, 02 Sep 2014 09:21:10 -0700 [thread overview]
Message-ID: <20140902162110.GB5001@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1409021052400.10607@gentwo.org>
[-- Attachment #1: Type: text/plain, Size: 817 bytes --]
On Tue, Sep 02, 2014 at 11:00:12AM -0500, Christoph Lameter wrote:
> On Tue, 2 Sep 2014, Paul E. McKenney wrote:
>
> > Before this commit, raw_cpu_add_return() didn't build. The commit
> > didn't affect anything else.
> >
> > So I don't understand how anything could work before this commit and
> > be broken after it. Enlightenment?
>
> Where is that raw_cpu_add_return statement?
>
> grep does not match anything like that in kernel/rcu/*
> and this_cpu_add_return is used extensively in the network subsystem for
> statistics.
Heh! Good point!
Added by ac1bea85781e (sched,rcu: Make cond_resched() report RCU quiescent
states), removed by 4a81e8328d379 (rcu: Reduce overhead of cond_resched()
checks for RCU). So, as you say, no effect on contemporary kernels.
Thanx, Paul
WARNING: multiple messages have this Message-ID (diff)
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>,
Jet Chen <jet.chen@intel.com>, Su Tao <tao.su@intel.com>,
Yuanhan Liu <yuanhan.liu@intel.com>, LKP <lkp@01.org>,
linux-kernel@vger.kernel.org
Subject: Re: [percpu] BUG: unable to handle kernel NULL pointer dereference at (null)
Date: Tue, 2 Sep 2014 09:21:10 -0700 [thread overview]
Message-ID: <20140902162110.GB5001@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.DEB.2.11.1409021052400.10607@gentwo.org>
On Tue, Sep 02, 2014 at 11:00:12AM -0500, Christoph Lameter wrote:
> On Tue, 2 Sep 2014, Paul E. McKenney wrote:
>
> > Before this commit, raw_cpu_add_return() didn't build. The commit
> > didn't affect anything else.
> >
> > So I don't understand how anything could work before this commit and
> > be broken after it. Enlightenment?
>
> Where is that raw_cpu_add_return statement?
>
> grep does not match anything like that in kernel/rcu/*
> and this_cpu_add_return is used extensively in the network subsystem for
> statistics.
Heh! Good point!
Added by ac1bea85781e (sched,rcu: Make cond_resched() report RCU quiescent
states), removed by 4a81e8328d379 (rcu: Reduce overhead of cond_resched()
checks for RCU). So, as you say, no effect on contemporary kernels.
Thanx, Paul
next prev parent reply other threads:[~2014-09-02 16:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-02 4:58 [percpu] BUG: unable to handle kernel NULL pointer dereference at (null) Fengguang Wu
2014-09-02 4:58 ` Fengguang Wu
2014-09-02 15:34 ` Paul E. McKenney
2014-09-02 15:34 ` Paul E. McKenney
2014-09-02 16:00 ` Christoph Lameter
2014-09-02 16:00 ` Christoph Lameter
2014-09-02 16:21 ` Paul E. McKenney [this message]
2014-09-02 16:21 ` Paul E. McKenney
2014-09-02 16:55 ` Christoph Lameter
2014-09-02 16:55 ` Christoph Lameter
2014-09-02 17:16 ` Paul E. McKenney
2014-09-02 17:16 ` Paul E. McKenney
2014-09-04 12:38 ` Fengguang Wu
2014-09-04 12:38 ` Fengguang Wu
2014-09-04 16:04 ` Paul E. McKenney
2014-09-04 16:04 ` Paul E. McKenney
2014-09-13 12:41 ` Fengguang Wu
2014-09-13 12:41 ` Fengguang Wu
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