Subject: lockdep warning with 2d65a9f48fcdf7866aab6457bc707ca233e0c791

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 15 Oct 2014 22:58:45 +0530

=============================================
[ INFO: possible recursive locking detected ]
3.17.0+ #31 Not tainted
---------------------------------------------
qemu-system-ppc/9112 is trying to acquire lock:
 (&(&vcpu->arch.tbacct_lock)->rlock){......}, at: [<d000000011591f84>] .vcore_stolen_time+0x44/0xb0 [kvm_hv]

but task is already holding lock:
 (&(&vcpu->arch.tbacct_lock)->rlock){......}, at: [<d000000011592524>] .kvmppc_remove_runnable.part.2+0x34/0xd0 [kvm_hv]

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&(&vcpu->arch.tbacct_lock)->rlock);
  lock(&(&vcpu->arch.tbacct_lock)->rlock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

3 locks held by qemu-system-ppc/9112:
 #0:  (&vcpu->mutex){+.+.+.}, at: [<c00000000008687c>] .vcpu_load+0x2c/0xf0
 #1:  (&(&vcore->lock)->rlock){+.+...}, at: [<d000000011594790>] .kvmppc_vcpu_run_hv+0x770/0x1720 [kvm_hv]
 #2:  (&(&vcpu->arch.tbacct_lock)->rlock){......}, at: [<d000000011592524>] .kvmppc_remove_runnable.part.2+0x34/0xd0 [kvm_hv]

stack backtrace:
CPU: 56 PID: 9112 Comm: qemu-system-ppc Not tainted 3.17.0+ #31
Call Trace:
[c000000fe488f330] [c0000000000167dc] .show_stack+0x7c/0x1f0 (unreliable)
[c000000fe488f400] [c0000000008ea148] .dump_stack+0x9c/0xd8
[c000000fe488f480] [c000000000110c6c] .__lock_acquire+0x151c/0x1ef0
[c000000fe488f600] [c000000000111fb0] .lock_acquire+0xd0/0x1b0
[c000000fe488f6d0] [c0000000008ddedc] ._raw_spin_lock_irq+0x5c/0x80
[c000000fe488f760] [d000000011591f84] .vcore_stolen_time+0x44/0xb0 [kvm_hv]
[c000000fe488f7f0] [d00000001159253c] .kvmppc_remove_runnable.part.2+0x4c/0xd0 [kvm_hv]
[c000000fe488f890] [d0000000115950c0] .kvmppc_vcpu_run_hv+0x10a0/0x1720 [kvm_hv]
[c000000fe488f9f0] [c000000000091d1c] .kvmppc_vcpu_run+0x2c/0x40
[c000000fe488fa60] [c00000000008efd4] .kvm_arch_vcpu_ioctl_run+0x54/0x170
[c000000fe488faf0] [c000000000086f78] .kvm_vcpu_ioctl+0x5c8/0x780
[c000000fe488fcb0] [c000000000264b54] .do_vfs_ioctl+0x474/0x770
[c000000fe488fd90] [c000000000264ea8] .SyS_ioctl+0x58/0xb0
[c000000fe488fe30] [c000000000009264] syscall_exit+0x0/0x98