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    Subject[PATCH tip/core/rcu 25/48] rcu: fix debugobjects rcu head init on stack in rcutree_plugin.h
    Date
    From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

    Testing resulted in the following debugobjects splat
    [...]
    ODEBUG: object is on stack, but not annotated
    ------------[ cut here ]------------
    Badness at lib/debugobjects.c:294
    NIP: c0000000002c76f0 LR: c0000000002c76ec CTR: c00000000041ecd8
    REGS: c0000001de71b280 TRAP: 0700 Tainted: G W (2.6.34-rc3-autokern1)
    MSR: 8000000000029032 <EE,ME,CE,IR,DR> CR: 24000424 XER: 0000000f
    TASK = c0000001de7dca00[3695] 'arping' THREAD: c0000001de718000 CPU: 1
    GPR00: c0000000002c76ec c0000001de71b500 c00000000096c048 0000000000000034
    GPR04: 0000000000000001 c000000000063918 0000000000000000 0000000000000002
    GPR08: 0000000000000003 0000000000000000 c000000000086f68 c0000001de7dca00
    GPR12: 000000000000256d c0000000074e4200 0000000000000000 0000000000000000
    GPR16: 0000000000000000 0000000000000000 0000000000000000 00000000201b8f60
    GPR20: 00000000201b8f70 00000000201b8f48 0000000000000000 c0000000008766b8
    GPR24: c0000001de71b800 0000000000000001 c0000000008ad400 c000000001247478
    GPR28: c0000000e6abb8c0 c0000000e6abb8c0 c000000000904570 c000000001247470
    NIP [c0000000002c76f0] .__debug_object_init+0x314/0x40c
    LR [c0000000002c76ec] .__debug_object_init+0x310/0x40c
    Call Trace:
    [c0000001de71b500] [c0000000002c76ec] .__debug_object_init+0x310/0x40c (unreliable)
    [c0000001de71b5d0] [c00000000007d990] .rcuhead_fixup_activate+0x40/0xdc
    [c0000001de71b660] [c0000000002c6a7c] .debug_object_fixup+0x4c/0x74
    [c0000001de71b6f0] [c0000000000c5e54] .__call_rcu+0x3c/0x1d4
    [c0000001de71b790] [c0000000000c6050] .synchronize_rcu+0x4c/0x6c
    [c0000001de71b870] [c0000000004be218] .synchronize_net+0x10/0x24
    [c0000001de71b8e0] [c0000000005498c8] .packet_release+0x1d4/0x274
    [c0000001de71b990] [c0000000004ac1f0] .sock_release+0x54/0x124
    [c0000001de71ba20] [c0000000004ac9e4] .sock_close+0x34/0x4c
    [c0000001de71baa0] [c00000000012469c] .__fput+0x174/0x264
    [c0000001de71bb40] [c000000000120c54] .filp_close+0xb0/0xd8
    [c0000001de71bbd0] [c000000000065e70] .put_files_struct+0x1a8/0x314
    [c0000001de71bc70] [c000000000067e04] .do_exit+0x234/0x6f0
    [c0000001de71bd30] [c000000000068354] .do_group_exit+0x94/0xc8
    [c0000001de71bdc0] [c00000000006839c] .SyS_exit_group+0x14/0x28
    [c0000001de71be30] [c000000000008554] syscall_exit+0x0/0x40
    Instruction dump:
    7f80b000 419e0030 2fa00000 e93e8140 380b0001 90090000 419e000c e87e8148
    48000008 e87e8150 4bd9cb89 60000000 <0fe00000> 801c0010 2f800003 419e0024

    The fix is to add init_rcu_head_on_stack() and destroy_rcu_head_on_stack()
    to the TREE_PREEMPT_RCU implementation of synchronize_rcu().

    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    kernel/rcutree_plugin.h | 2 ++
    1 files changed, 2 insertions(+), 0 deletions(-)

    diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
    index 0ae2339..5c599e8 100644
    --- a/kernel/rcutree_plugin.h
    +++ b/kernel/rcutree_plugin.h
    @@ -557,11 +557,13 @@ void synchronize_rcu(void)
    if (!rcu_scheduler_active)
    return;

    + init_rcu_head_on_stack(&rcu.head);
    init_completion(&rcu.completion);
    /* Will wake me after RCU finished. */
    call_rcu(&rcu.head, wakeme_after_rcu);
    /* Wait for it. */
    wait_for_completion(&rcu.completion);
    + destroy_rcu_head_on_stack(&rcu.head);
    }
    EXPORT_SYMBOL_GPL(synchronize_rcu);

    --
    1.7.0


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