• Gavin Shan's avatar
    powerpc/pseries: Avoid deadlock on removing ddw · 54bd94f7
    Gavin Shan authored
    commit 5efbabe0 upstream.
    
    Function remove_ddw() could be called in of_reconfig_notifier and
    we potentially remove the dynamic DMA window property, which invokes
    of_reconfig_notifier again. Eventually, it leads to the deadlock as
    following backtrace shows.
    
    The patch fixes the above issue by deferring releasing the dynamic
    DMA window property while releasing the device node.
    
    =============================================
    [ INFO: possible recursive locking detected ]
    3.16.0+ #428 Tainted: G        W
    ---------------------------------------------
    drmgr/2273 is trying to acquire lock:
     ((of_reconfig_chain).rwsem){.+.+..}, at: [<c000000000091890>] \
     .__blocking_notifier_call_chain+0x40/0x78
    
    but task is already holding lock:
     ((of_reconfig_chain).rwsem){.+.+..}, at: [<c000000000091890>] \
     .__blocking_notifier_call_chain+0x40/0x78
    
    other info that might help us debug this:
     Possible unsafe locking scenario:
    
           CPU0
           ----
      lock((of_reconfig_chain).rwsem);
      lock((of_reconfig_chain).rwsem);
     *** DEADLOCK ***
    
     May be due to missing lock nesting notation
    
    2 locks held by drmgr/2273:
     #0:  (sb_writers#4){.+.+.+}, at: [<c0000000001cbe70>] \
          .vfs_write+0xb0/0x1f8
     #1:  ((of_reconfig_chain).rwsem){.+.+..}, at: [<c000000000091890>] \
          .__blocking_notifier_call_chain+0x40/0x78
    
    stack backtrace:
    CPU: 17 PID: 2273 Comm: drmgr Tainted: G        W     3.16.0+ #428
    Call Trace:
    [c0000000137e7000] [c000000000013d9c] .show_stack+0x88/0x148 (unreliable)
    [c0000000137e70b0] [c00000000083cd34] .dump_stack+0x7c/0x9c
    [c0000000137e7130] [c0000000000b8afc] .__lock_acquire+0x128c/0x1c68
    [c0000000137e7280] [c0000000000b9a4c] .lock_acquire+0xe8/0x104
    [c0000000137e7350] [c00000000083588c] .down_read+0x4c/0x90
    [c0000000137e73e0] [c000000000091890] .__blocking_notifier_call_chain+0x40/0x78
    [c0000000137e7490] [c000000000091900] .blocking_notifier_call_chain+0x38/0x48
    [c0000000137e7520] [c000000000682a28] .of_reconfig_notify+0x34/0x5c
    [c0000000137e75b0] [c000000000682a9c] .of_property_notify+0x4c/0x54
    [c0000000137e7650] [c000000000682bf0] .of_remove_property+0x30/0xd4
    [c0000000137e76f0] [c000000000052a44] .remove_ddw+0x144/0x168
    [c0000000137e7790] [c000000000053204] .iommu_reconfig_notifier+0x30/0xe0
    [c0000000137e7820] [c00000000009137c] .notifier_call_chain+0x6c/0xb4
    [c0000000137e78c0] [c0000000000918ac] .__blocking_notifier_call_chain+0x5c/0x78
    [c0000000137e7970] [c000000000091900] .blocking_notifier_call_chain+0x38/0x48
    [c0000000137e7a00] [c000000000682a28] .of_reconfig_notify+0x34/0x5c
    [c0000000137e7a90] [c000000000682e14] .of_detach_node+0x44/0x1fc
    [c0000000137e7b40] [c0000000000518e4] .ofdt_write+0x3ac/0x688
    [c0000000137e7c20] [c000000000238430] .proc_reg_write+0xb8/0xd4
    [c0000000137e7cd0] [c0000000001cbeac] .vfs_write+0xec/0x1f8
    [c0000000137e7d70] [c0000000001cc3b0] .SyS_write+0x58/0xa0
    [c0000000137e7e30] [c00000000000a064] syscall_exit+0x0/0x98
    Signed-off-by: default avatarGavin Shan <gwshan@linux.vnet.ibm.com>
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    54bd94f7
iommu.c 36 KB