Here is another strace log, for gnome-calculator. It pauses at line 3755: ------ 3738 [pid 10510] poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout) 3739 [pid 10510] poll([{fd=5, events=POLLIN}], 1, 0) = 1 ([{fd=5, revents=POLLIN}]) 3740 [pid 10510] recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\2\1\1\0\0\0\0\n\0\0\0005\0\0\0", iov_len=16}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG _CMSG_CLOEXEC) = 16 3741 [pid 10510] poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout) 3742 [pid 10510] poll([{fd=5, events=POLLIN}], 1, 0) = 1 ([{fd=5, revents=POLLIN}]) 3743 [pid 10510] recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\6\1s\0\6\0\0\0:1.343\0\0\5\1u\0\t\0\0\0\7\1s\0\24\0\0\0"..., iov_len=56}], msg_iovlen=1, msg_controllen=0, msg_f lags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 56 3744 [pid 10510] poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout) 3745 [pid 10510] poll([{fd=5, events=POLLIN}], 1, 0) = 1 ([{fd=5, revents=POLLIN}]) 3746 [pid 10510] recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="l\2\1\1\0\0\0\0\v\0\0\0005\0\0\0", iov_len=16}], msg_iovlen=1, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG _CMSG_CLOEXEC) = 16 3747 [pid 10510] poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout) 3748 [pid 10510] poll([{fd=5, events=POLLIN}], 1, 0) = 1 ([{fd=5, revents=POLLIN}]) 3749 [pid 10510] recvmsg(5, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\6\1s\0\6\0\0\0:1.343\0\0\5\1u\0\n\0\0\0\7\1s\0\24\0\0\0"..., iov_len=56}], msg_iovlen=1, msg_controllen=0, msg_f lags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 56 3750 [pid 10510] poll([{fd=6, events=POLLIN}], 1, 0) = 0 (Timeout) 3751 [pid 10510] poll([{fd=5, events=POLLIN}], 1, 0) = 0 (Timeout) 3752 [pid 10510] write(6, "\1\0\0\0\0\0\0\0", 8) = 8 3753 [pid 10510] poll([{fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 2, -1) = 1 ([{fd=6, revents=POLLIN}]) 3754 [pid 10510] read(6, "\1\0\0\0\0\0\0\0", 16) = 8 3755 [pid 10510] poll([{fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 2, -1 3756 [pid 10508] <... poll resumed> ) = 0 (Timeout) ------