## Status Bug still occurs every few days, when I use Ubuntu 16.04, not when using others.
## Trying to get more precise info ### Location in source code Following https://wiki.ubuntu.com/DebuggingProgramCrash I could get an interactive gdb prompt showing that it's blocked in the while loop below: term-utils/script.c lines 278-287: static void wait_for_empty_fd(int fd) { struct pollfd fds[] = { { .fd = fd, .events = POLLIN } }; while (poll(fds, 1, 10) == 1) { DBG(IO, ul_debug(" data to read")); } } ### Activity at debugger level Here's the gdb log of the loop when pressing return key at each prompt repeats "step" gdb command: wait_for_empty_fd (fd=<optimized out>) at term-utils/script.c:284 284 while (poll(fds, 1, 10) == 1) { (gdb) 285 DBG(IO, ul_debug(" data to read")); (gdb) 284 while (poll(fds, 1, 10) == 1) { (gdb) poll (__timeout=10, __nfds=1, __fds=0x7fffd0eff840) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46 46 return __poll_alias (__fds, __nfds, __timeout); (gdb) poll () at ../sysdeps/unix/syscall-template.S:84 84 ../sysdeps/unix/syscall-template.S: Aucun fichier ou dossier de ce type. (gdb) (gdb) bt #0 poll (__timeout=10, __nfds=1, __fds=0x7fffd0eff840) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46 #1 wait_for_empty_fd (fd=<optimized out>) at term-utils/script.c:284 #2 write_to_shell (ctl=ctl@entry=0x7fffd0f019c0, buf=buf@entry=0x7fffd0eff890 "sometext"..., bufsz=bufsz@entry=1) at term-utils/script.c:303 #3 0x0000000000402e6d in handle_io (ctl=ctl@entry=0x7fffd0f019c0, fd=0, eof=eof@entry=0x7fffd0f01904) at term-utils/script.c:346 #4 0x00000000004023fb in do_io (ctl=0x7fffd0f019c0) at term-utils/script.c:475 #5 main (argc=<optimized out>, argv=<optimized out>) at term-utils/script.c:781 (gdb) print __fds $1 = (struct pollfd *) 0x7fffd0eff840 (gdb) print *__fds $2 = {fd = 4, events = 1, revents = 1} lrwx------ 1 stephane stephane 64 Apr 5 16:38 0 -> /dev/pts/6 lrwx------ 1 stephane stephane 64 Apr 5 16:38 1 -> /dev/pts/6 lrwx------ 1 stephane stephane 64 Apr 5 16:38 2 -> /dev/pts/6 lrwx------ 1 stephane stephane 64 Apr 5 16:38 3 -> /dev/ptmx lrwx------ 1 stephane stephane 64 Apr 5 16:38 4 -> /dev/pts/21 lrwx------ 1 stephane stephane 64 Apr 5 16:38 5 -> anon_inode:[signalfd] l-wx------ 1 stephane stephane 64 Apr 5 16:38 6 -> /tmp/myscriptfile.txt l-wx------ 1 stephane stephane 64 Apr 5 16:38 7 -> /tmp/myscriptfile.timings ## Summary * "script" polls slave pts at high speed consuming 100% CPU, assuming this won't last. But sometimes it does last forever. * Polling code was introduced in commit below: commit 54c6611d6f7b73609a5331f4d0bcf63c4af6429e Author: Karel Zak <k...@redhat.com> Date: Wed Jun 17 15:48:50 2015 +0200 script: fix EOF problems * remove STDIN from poll() if: * STDIN already closed -- poll returns POLLHUP, for example: echo "date" | script * detect EOF as returned by read(), for example: script -c "echo Hello" < /dev/null * don't write to master when there is still something to read from slave (it means shell is not initialized yet or busy) Signed-off-by: Karel Zak <k...@redhat.com> ## Now what ? What should be changed? It script to blame or is is the shell? Additional info: exact same operation (shell, etc) have been performed for years, no problem. Even on this distro (Ubuntu 16.04) it usually works. It *always* works on Ubuntu <=15.10, Debian 8.3, Fedora 23. How to debug further? -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to util-linux in Ubuntu. https://bugs.launchpad.net/bugs/1558236 Title: /usr/bin/script freezes and eats all CPU, has to be killed, which kills shell and programs inside Status in util-linux package in Ubuntu: New Bug description: # Context I've been using /usr/bin/script quite a lot for about 4 years (since about Ubuntu 12.04, maybe before). It always worked without problem. I'm using several script instance most of the time, in several terminals. Reproducible: randomly, once every few days. Problem happens since Ubuntu 16.04. Never seen before (12.04 12.10 13.04 13.10 14.04 14.10 15.04 15.10). # Expected Continued operation, terminal running programs normally, little CPU used. # Observed Suddenly, terminal freezes. Other tabs of same terminal window not affected. Top shows script consumes 100% CPU. Strace shows an endless stream of this line: poll([{fd=4, events=POLLIN}], 1, 10) = 1 ([{fd=4, revents=POLLIN}]) /proc/*/fd shows what file descriptor it is: total 0 dr-x------ 2 stephane stephane 0 mars 16 20:03 . dr-xr-xr-x 9 stephane stephane 0 mars 16 20:03 .. lrwx------ 1 stephane stephane 64 mars 16 20:15 0 -> /dev/pts/17 (deleted) lrwx------ 1 stephane stephane 64 mars 16 20:15 1 -> /dev/pts/17 (deleted) lrwx------ 1 stephane stephane 64 mars 16 20:03 2 -> /dev/pts/17 (deleted) lrwx------ 1 stephane stephane 64 mars 16 20:15 3 -> /dev/ptmx lrwx------ 1 stephane stephane 64 mars 16 20:15 4 -> /dev/pts/21 lrwx------ 1 stephane stephane 64 mars 16 20:15 5 -> anon_inode:[signalfd] l-wx------ 1 stephane stephane 64 mars 16 20:15 6 -> /somewhere/mylogfile.txt l-wx------ 1 stephane stephane 64 mars 16 20:15 7 -> /somewhere/mylogfile_timings.txt What can we do? ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: bsdutils 1:2.27.1-6ubuntu1 ProcVersionSignature: Ubuntu 4.4.0-13.29-generic 4.4.5 Uname: Linux 4.4.0-13-generic x86_64 ApportVersion: 2.20-0ubuntu3 Architecture: amd64 CurrentDesktop: XFCE Date: Wed Mar 16 20:04:02 2016 ExecutablePath: /usr/bin/script InstallationDate: Installed on 2016-02-03 (41 days ago) InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160203) SourcePackage: util-linux UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1558236/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
