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    Subject[3.12-rc] sg_open: leaving the kernel with locks still held!
    Hello!

    While trying to figure out why the request queue to sda (ext4) was
    clogging up on one of our btrfs backup boxes, I noticed a megarc process
    in D state, so enabled locking debugging, and got this (on 3.12-rc6):

    [ 205.372823] ================================================
    [ 205.372901] [ BUG: lock held when returning to user space! ]
    [ 205.372979] 3.12.0-rc6-hw-debug-pagealloc+ #67 Not tainted
    [ 205.373055] ------------------------------------------------
    [ 205.373132] megarc.bin/5283 is leaving the kernel with locks still held!
    [ 205.373212] 1 lock held by megarc.bin/5283:
    [ 205.373285] #0: (&sdp->o_sem){.+.+..}, at: [<ffffffff8161e650>] sg_open+0x3a0/0x4d0

    Vaughan, it seems you touched this area last in 15b06f9a02406e, and git
    tag --contains says this went in for 3.12-rc. We didn't see this on 3.11,
    though I haven't tried with lockdep.

    This is caused by some of our internal RAID monitoring scripts that run
    "megarc.bin -dispCfg -a0" (even though that controller isn't present on
    this server -- a PowerEdge 2950 w/Perc 5).

    strace output of the program execution that causes the above message is
    here: http://0x.ca/sim/ref/3.12-rc6/megarc_strace.txt

    Simon-


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