## 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 Bugs, which is subscribed to 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1558236/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
