Messages in this thread | | | Date | Fri, 21 Nov 2014 16:58:17 +0200 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH tip/core/rcu 3/9] drivers/md: Use rcu_dereference() for accessing rcu pointer |
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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
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