other: 0.907 permissions: 0.859 graphic: 0.850 KVM: 0.841 semantic: 0.824 debug: 0.820 performance: 0.817 vnc: 0.811 device: 0.809 PID: 0.794 files: 0.788 socket: 0.755 network: 0.701 boot: 0.698 qemu hangs in pselect syscall I'm using git commit d75aa4372f0414c9960534026a562b0302fcff29 (v2.7.0-rc4) configured with; --enable-linux-user \ --disable-system \ --disable-tools \ --disable-guest-agent \ --static --disable-linux-aio \ --disable-fdt \ --without-pixman \ --disable-blobs \ Stable version (v2.6.0) also have the same problem. In a chroot environment I ran below command-line to compile some things, different sources each time. /usr/bin/qemu-arm -0 /usr/bin/edje_cc /usr/bin/edje_cc -id /home/abuild/rpmbuild/BUILD/org.tizen.browser-1.6.2/services/SimpleUI/images_mob/ -DBROWSER_RESOLUTION_720x1280=1 -DPROFILE_MOBILE=1 /home/abuild/rpmbuild/BUILD/org.tizen.browser-1.6.2/services/SimpleUI/edc/TextPopup_mob.edc /home/abuild/rpmbuild/BUILD/org.tizen.browser-1.6.2/build-tizen/services/SimpleUI/720x1280_TextPopup.edj Here is back trace with gdb; #0 safe_syscall_end () at /usr/src/debug/qemu-2.6.94/linux-user/host/i386/safe-syscall.inc.S:78 #1 0x60049370 in safe_pselect6 (nfds=10, readfds=0xffa31b5c, writefds=0xffa31bdc, exceptfds=0xffa31c5c, timeout=0x0, sig=0x0) at /usr/src/debug/qemu-2.6.94/linux-user/syscall.c:855 #2 0x6004b2fe in do_select (n=10, rfd_addr=1082122232, wfd_addr=1082122360, efd_addr=1082122488, target_tv_addr=0) at /usr/src/debug/qemu-2.6.94/linux-user/syscall.c:1386 #3 0x6005e5ba in do_syscall (cpu_env=0x640d0454, num=142, arg1=10, arg2=1082122232, arg3=1082122360, arg4=1082122488, arg5=0, arg6=1087473216, arg7=0, arg8=0) at /usr/src/debug/qemu-2.6.94/linux-user/syscall.c:9690 #4 0x60045def in cpu_loop (env=0x640d0454) at /usr/src/debug/qemu-2.6.94/linux-user/main.c:876 #5 0x60047640 in main (argc=10, argv=0xffa33c84, envp=0xffa33cb0) at /usr/src/debug/qemu-2.6.94/linux-user/main.c:4817 Attached core file taken from gdb. To see the stack frame, you could try; $ tar -xf reproduced_118_04.tar.bz2; gdb --core core.1823 qemu-arm And recent strace log for PID 1823(stucked one); 79965 [ 313s] 1823 :0x8e _newselect(10,[9,3,],[],[],NULL) 79966 [ 313s] ==>[pselect6(0xa)=] 79967 [ 313s] [pselect6=0x1]<== 79968 [ 313s] 1823 :0x8e _newselect(10,[9,],[],[],NULL) 79969 [ 313s] 1823 :0x8e => = 0x00000001 ([9,],[],[],NULL) 79970 [ 313s] 1823 :0xfc epoll_wait(3,1082121456,32,0,1082121456,3) 79971 [ 313s] 1823 :0xfc epoll_wait(3,1082121456,32,0,1082121456,3) 79972 [ 313s] 1823 :0xfc => = 0 79973 [ 313s] 1823 :0x3 read(9,0x407fdeec,16) 79974 [ 313s] 1823 :0x3 read(9,0x407fdeec,16) 79975 [ 313s] 1823 :0x3 => = 8 79976 [ 313s] 1823 :0x107 clock_gettime(1,1082122120,0,1082829144,1082827588,0) 79977 [ 313s] 1823 :0x107 clock_gettime(1,1082122120,0,1082829144,1082827588,0) 79978 [ 313s] 1823 :0x107 => = 0 79979 [ 313s] 1823 :0x8e _newselect(10,[9,3,],[],[],NULL) 79980 [ 313s] ==>[pselect6(0xa)=] I'm using 64-bit Ubuntu with kernel release Linux 3.19.0-25-generic #26~14.04.1-Ubuntu. Reproducibility is low. One occurrence out of 50+ trials. FYI, adding a build log with strace enabled. Can you provide sufficient instructions for me to reproduce this on my machine, please? Second part of scratch.armv7l.0.tar.gz. Third part of scratch.armv7l.0.tar.gz. Dear Peter. Thank you for the update. Please find the attached full chroot environment that I used(scratch.armv7l.0.tar.gz, split three parts). You could try make build with below steps; $ sudo su $ echo -1 > /proc/sys/fs/binfmt_misc/arm $ echo ':arm:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfa\xff\xff\xff:/usr/bin/qemu-arm-static:' > /proc/sys/fs/binfmt_misc/register $ cat scratch.armv7l.0.tar.gz.a* > scratch.armv7l.0.tar.gz; sudo tar -zxf scratch.armv7l.0.tar.gz $ cd scratch.armv7l.0 $ chroot . chroot> cd /home/abuild/rpmbuild/BUILD/org.tizen.browser-1.6.2/build-tizen/services/ chroot> while :; do make clean; make -j32; done Reproducibility is ver low but it surely happened. Thanks. I can't reproduce this with current git master, and I know we fixed a lot of race conditions in linux-user. So I'm going to close this bug -- if it's still a problem for you with new QEMU, please reopen, preferably with a repro case that's more frequent than 1-in-50-or-less.