powerpc/pseries: Avoid deadlock on removing ddw
authorGavin Shan <gwshan@linux.vnet.ibm.com>
Mon, 11 Aug 2014 09:16:20 +0000 (19:16 +1000)
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>
Wed, 13 Aug 2014 05:13:47 +0000 (15:13 +1000)
commit5efbabe09d986f25c02d19954660238fcd7f008a
tree9ed3958ab9e81e79d17362c6867e6aa35b91b259
parentf1b3929c232784580e5d8ee324b6bc634e709575
powerpc/pseries: Avoid deadlock on removing ddw

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>
arch/powerpc/platforms/pseries/iommu.c