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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 Cc: stable@vger.kernel.org Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> |
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