> kvm-all.c:kvm_cpu_exec: > qemu_mutex_unlock_iothread(); > ret = kvm_vcpu_ioctl(env, KVM_RUN, 0); > qemu_mutex_lock_iothread();
Thank you for the information. I also suspected that qemu_mutex_lock_iothread() does the synchronization. However, my profiling showed that qemu-kvm.c:kvm_cpu_exec() in is actually executed, instead of kvm-all.c:kvm_cpu_exec(). Also I previously profiled all executions of qemu_mutex_lock_iothread(), and found that it only protects the vl.c:main_loop_wai() thread but does NOT protect the qemu-kvm.c:kvm_cpu_exec() thread. Did I miss something or is this a defect? I did extensive profiling but still don't know the source code well enough to confidently draw a conclusion. For example, see the profiled execution sequence below. The kvm_cpu_exec() thread did not perform qemu_mutex_lock_iothread(). The locking was only performed by the vl.c:main_loop_wai() thread. home/ctang/kvm/qemu-kvm-0.12.3/qemu-kvm.c : 2530 thread: b7e056d0 /home/ctang/kvm/bin/qemu-system-x86_64(qemu_mutex_unlock_iothread+0x1a) [0x8092242] /home/ctang/kvm/bin/qemu-system-x86_64(main_loop_wait+0x221) [0x806edef] /home/ctang/kvm/bin/qemu-system-x86_64(kvm_main_loop+0x1ff) [0x80916a1] /home/ctang/kvm/bin/qemu-system-x86_64 [0x806f5c2] /home/ctang/kvm/bin/qemu-system-x86_64(main+0x2e2c) [0x80736d1] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xb7e33775] /home/ctang/kvm/bin/qemu-system-x86_64 [0x8068bb1] block/qcow2-cluster.c : 721 thread: b7dc2b90 /home/ctang/kvm/bin/qemu-system-x86_64(qcow2_alloc_cluster_offset+0x3c) [0x81175fa] /home/ctang/kvm/bin/qemu-system-x86_64(qcow_aio_write_cb+0x158) [0x8111d73] /home/ctang/kvm/bin/qemu-system-x86_64(qcow_aio_writev+0x94) [0x8112054] /home/ctang/kvm/bin/qemu-system-x86_64(bdrv_aio_writev+0xe1) [0x80fa8e9] /home/ctang/kvm/bin/qemu-system-x86_64 [0x81f4a96] /home/ctang/kvm/bin/qemu-system-x86_64 [0x81f4c04] /home/ctang/kvm/bin/qemu-system-x86_64(dma_bdrv_write+0x48) [0x81f4cbf] /home/ctang/kvm/bin/qemu-system-x86_64 [0x80a437c] /home/ctang/kvm/bin/qemu-system-x86_64(bmdma_cmd_writeb+0x73) [0x80a9503] /home/ctang/kvm/bin/qemu-system-x86_64 [0x812b1eb] /home/ctang/kvm/bin/qemu-system-x86_64(cpu_outb+0x27) [0x812b4e6] /home/ctang/kvm/bin/qemu-system-x86_64 [0x808d267] /home/ctang/kvm/bin/qemu-system-x86_64(kvm_run+0x2f4) [0x808f4b8] /home/ctang/kvm/bin/qemu-system-x86_64(kvm_cpu_exec+0x56) [0x80907b2] /home/ctang/kvm/bin/qemu-system-x86_64 [0x8090f4d] /home/ctang/kvm/bin/qemu-system-x86_64 [0x8091098] /lib/tls/i686/cmov/libpthread.so.0 [0xb7fd24ff] /lib/tls/i686/cmov/libc.so.6(clone+0x5e) [0xb7f0149e] /home/ctang/kvm/qemu-kvm-0.12.3/qemu-kvm.c : 2537 thread: b7e056d0 /home/ctang/kvm/bin/qemu-system-x86_64(qemu_mutex_lock_iothread+0x1a) [0x809229d] /home/ctang/kvm/bin/qemu-system-x86_64(main_loop_wait+0x25c) [0x806ee2a] /home/ctang/kvm/bin/qemu-system-x86_64(kvm_main_loop+0x1ff) [0x80916a1] /home/ctang/kvm/bin/qemu-system-x86_64 [0x806f5c2] /home/ctang/kvm/bin/qemu-system-x86_64(main+0x2e2c) [0x80736d1] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe5) [0xb7e33775] /home/ctang/kvm/bin/qemu-system-x86_64 [0x8068bb1]