8681 2015-11-11 18:10:44 +0000 qemu runs out of entropy, hangs on getrandom() syscall 2016-03-07 06:29:44 +0000 1 1 11 Runtime General Runtime General Runtime unspecified x86 Multiple RESOLVED FIXED Medium+ normal 2.1 M3 8816 1 alejandro.hernandez sgw alexandru.c.georgescu randy.macleod francisco.j.pedraza.gonzalez --- --- No (bug/feature does not impact docs) oldest_to_newest 56394 0 alejandro.hernandez 2015-11-11 18:10:44 +0000 After running qemu on a certain headless host, trying to run python3 (and likely others) hangs, after doing an strace I can see that its hanging when trying to get a random number: ... set_thread_area({entry_number:-1, base_addr:0xb7742700, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0 (entry_number:6) mprotect(0x464dc000, 8192, PROT_READ) = 0 mprotect(0x46568000, 4096, PROT_READ) = 0 mprotect(0x464e7000, 4096, PROT_READ) = 0 mprotect(0x46506000, 4096, PROT_READ) = 0 mprotect(0x4668d000, 4096, PROT_READ) = 0 mprotect(0x46362000, 4096, PROT_READ) = 0 munmap(0xb7745000, 5836) = 0 set_tid_address(0xb7742768) = 255 set_robust_list(0xb7742770, 12) = 0 rt_sigaction(SIGRTMIN, {0x46553920, [], SA_SIGINFO}, NULL, 8) = 0 rt_sigaction(SIGRT_1, {0x465539b0, [], SA_RESTART|SA_SIGINFO}, NULL, 8) = 0 rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0 ugetrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM_INFINITY}) = 0 uname({sysname="Linux", nodename="qemux86", ...}) = 0 brk(0) = 0x804b000 brk(0x806c000) = 0x806c000 getrandom( ... Checking available entropy on qemu shows: # sysctl kernel.random.entropy_avail kernel.random.entropy_avail = 0 Checking available entropy on the host shows: kernel.random.entropy_avail = 185 Cristian Iorga suggested using: http://wiki.qemu-project.org/Features/VirtIORNG nonetheless, neither the qemu machine or the host contain the file /dev/hwrng, so this didn't solve it. Ross Burton suggested doing a find / # sysctl kernel.random.entropy_avail kernel.random.entropy_avail = 0 # find / . * Lots of output * . # sysctl kernel.random.entropy_avail kernel.random.entropy_avail = 848 # python3 Python 3.5.0 (default, Nov 11 2015, 00:30:30) [GCC 5.2.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> So generating output to the terminal, generates entropy and solves the issue, although we still don;t know what caused the problem in the first place. After rebooting qemu, the issue shows up again... 58833 1 sgw 2016-02-10 16:58:01 +0000 Pushing to M3 due to change of resources 59038 2 sgw 2016-02-15 17:02:26 +0000 These two patches add rng-tools to the qemu images and increase the availablity of entropy bits http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=6740dd55798641a47744b891aa1d8fa5e04c2cdc http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=ce3df21122d7fc4ede6fe36009afb297004672ef