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    SubjectRe: RCU idle CPU detection is broken in linux-next
    On Wed, Sep 19, 2012 at 06:35:36PM +0200, Sasha Levin wrote:
    > On 09/19/2012 05:39 PM, Paul E. McKenney wrote:
    > > On Wed, Sep 12, 2012 at 07:56:48PM +0200, Sasha Levin wrote:
    > >> > Hi Paul,
    > >> >
    > >> > While fuzzing using trinity inside a KVM tools guest, I've managed to trigger
    > >> > "RCU used illegally from idle CPU!" warnings several times.
    > >> >
    > >> > There are a bunch of traces which seem to pop exactly at the same time and from
    > >> > different places around the kernel. Here are several of them:
    > > Hello, Sasha,
    > >
    > > OK, interesting. Could you please try reproducing with the diagnostic
    > > patch shown below?
    >
    > Sure - here are the results (btw, it reproduces very easily):
    >
    > [ 13.525119] ================================================
    > [ 13.527165] [ BUG: lock held when returning to user space! ]
    > [ 13.528752] 3.6.0-rc6-next-20120918-sasha-00002-g190c311-dirty #362 Tainted: GW
    > [ 13.531314] ------------------------------------------------
    > [ 13.532918] init/1 is leaving the kernel with locks still held!
    > [ 13.534574] 1 lock held by init/1:
    > [ 13.535533] #0: (rcu_idle){.+.+..}, at: [<ffffffff811c36d0>]
    > rcu_eqs_enter_common+0x1a0/0x9a0
    >
    > I'm basically seeing lots of the above, so I can't even get to the point where I
    > get the previous lockdep warnings.

    OK, that diagnostic patch was unhelpful. Back to the drawing board...

    Thanx, Paul



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