On 03/16/2011 06:37 PM, Bharat Bhushan wrote:
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.
Seems excessive to have a new lock just for timing.
What about using vcpu->requests to have the statistics cleared in vcpu
context?
What about dropping the whole thing and replacing it with tracepoints?
--
error compiling committee.c: too many arguments to function
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