From 09000adb86550d2895b64faa52e64eaec3cae7b2 Mon Sep 17 00:00:00 2001 From: Bharat Bhushan Date: Fri, 25 Mar 2011 10:32:13 +0530 Subject: KVM: PPC: Fix issue clearing exit timing counters Following dump is observed on host when clearing the exit timing counters [root@p1021mds kvm]# echo -n 'c' > vm1200_vcpu0_timing INFO: task echo:1276 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. echo D 0ff5bf94 0 1276 1190 0x00000000 Call Trace: [c2157e40] [c0007908] __switch_to+0x9c/0xc4 [c2157e50] [c040293c] schedule+0x1b4/0x3bc [c2157e90] [c04032dc] __mutex_lock_slowpath+0x74/0xc0 [c2157ec0] [c00369e4] kvmppc_init_timing_stats+0x20/0xb8 [c2157ed0] [c0036b00] kvmppc_exit_timing_write+0x84/0x98 [c2157ef0] [c00b9f90] vfs_write+0xc0/0x16c [c2157f10] [c00ba284] sys_write+0x4c/0x90 [c2157f40] [c000e320] ret_from_syscall+0x0/0x3c The vcpu->mutex is used by kvm_ioctl_* (KVM_RUN etc) and same was used when clearing the stats (in kvmppc_init_timing_stats()). What happens is that when the guest is idle then it held the vcpu->mutx. While the exiting timing process waits for guest to release the vcpu->mutex and a hang state is reached. Now using seprate lock for exit timing stats. Signed-off-by: Bharat Bhushan Acked-by: Alexander Graf Signed-off-by: Avi Kivity --- arch/powerpc/kvm/powerpc.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/powerpc/kvm/powerpc.c') diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 99758460efde..ec3d2e75c0a8 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -284,6 +284,10 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) tasklet_init(&vcpu->arch.tasklet, kvmppc_decrementer_func, (ulong)vcpu); vcpu->arch.dec_timer.function = kvmppc_decrementer_wakeup; +#ifdef CONFIG_KVM_EXIT_TIMING + mutex_init(&vcpu->arch.exit_timing_lock); +#endif + return 0; } -- cgit v1.2.3