From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Pranith Kumar <bobby.prani@gmail.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
linux-kernel@vger.kernel.org, mingo@kernel.org,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com
Subject: Re: [PATCH tip/core/rcu 3/9] drivers/md: Use rcu_dereference() for accessing rcu pointer
Date: Fri, 21 Nov 2014 16:58:17 +0200 [thread overview]
Message-ID: <20141121145817.GA17710@node.dhcp.inet.fi> (raw)
In-Reply-To: <546F4C8C.4040904@gmail.com>
On Fri, Nov 21, 2014 at 09:30:36AM -0500, Pranith Kumar wrote:
> On 11/21/2014 08:31 AM, Kirill A. Shutemov wrote:
> > On Tue, Oct 28, 2014 at 03:09:56PM -0700, Paul E. McKenney wrote:
> >> From: Pranith Kumar <bobby.prani@gmail.com>
> >>
> >> Got Paul's email wrong the first time.
> >>
> >> The map field in 'struct mapped_device' is an rcu pointer. Use rcu_dereference()
> >> while accessing it.
> >>
> >> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
> >> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> >
> > On current -next I see this:
> >
> > [ 6.388264] ===============================
> > [ 6.389571] [ INFO: suspicious RCU usage. ]
> > [ 6.390869] 3.18.0-rc5-next-20141121-08303-g44cae4530372 #2 Not tainted
> > [ 6.392185] -------------------------------
> > [ 6.393479] /home/kas/git/public/linux/drivers/md/dm.c:2853 suspicious rcu_dereference_check() usage!
> > [ 6.394801]
> > other info that might help us debug this:
> >
>
> Hi Kirill,
>
> We are dereferencing an RCU pointer with the suspend_lock held which is causing this warning.
>
> Can you please check if the following patch helps? Thanks!
Nope. The same issue.
IIUC, the problem is that you dereference pointer outside rcu_read_lock()
section, not that suspend_lock is held.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2014-11-21 14:59 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-28 22:09 [PATCH tip/core/rcu 0/9] Miscellaneous fixes for 3.19 Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 1/9] rcu: Remove CONFIG_RCU_CPU_STALL_VERBOSE Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 2/9] compiler: Allow 1- and 2-byte smp_load_acquire() and smp_store_release() Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 3/9] drivers/md: Use rcu_dereference() for accessing rcu pointer Paul E. McKenney
2014-11-21 13:31 ` Kirill A. Shutemov
2014-11-21 14:30 ` Pranith Kumar
2014-11-21 14:58 ` Kirill A. Shutemov [this message]
2014-11-23 12:21 ` Pranith Kumar
2014-11-23 16:39 ` Eric Dumazet
2014-11-23 16:40 ` [PATCH ] drivers/md: use proper rcu accessor Eric Dumazet
2014-11-23 16:53 ` Mike Snitzer
2014-11-23 17:31 ` Eric Dumazet
2014-11-23 19:12 ` Mike Snitzer
2014-11-23 17:34 ` [PATCH v2] " Eric Dumazet
2014-11-24 4:09 ` Mike Snitzer
2014-10-28 22:09 ` [PATCH tip/core/rcu 4/9] dm: sparse: Annotate field with __rcu for checking Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 5/9] rcu: Add sparse check for RCU_INIT_POINTER() Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 6/9] rcu: Optimize cond_resched_rcu_qs() Paul E. McKenney
2014-10-28 22:10 ` [PATCH tip/core/rcu 7/9] rcu: More info about potential deadlocks with rcu_read_unlock() Paul E. McKenney
2014-10-28 22:10 ` [PATCH tip/core/rcu 8/9] rcu: Fix FIXME in rcu_tasks_kthread() Paul E. McKenney
2014-10-28 22:10 ` [PATCH tip/core/rcu 9/9] rcu: Provide counterpart to rcu_dereference() for non-RCU situations Paul E. McKenney
2014-10-29 10:57 ` Peter Zijlstra
2014-10-29 12:42 ` Paul E. McKenney
2014-10-29 19:15 ` Oleg Nesterov
2014-10-29 18:43 ` Paul E. McKenney
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