[ovs-git] [openvswitch/ovs] ecd4a8: fatal-signal: Log backtrace when no monitor daemon.

William Tu noreply at github.com
Mon Mar 23 16:43:28 UTC 2020

  Branch: refs/heads/master
  Home:   https://github.com/openvswitch/ovs
  Commit: ecd4a8fcdff2ebf35cdb36355167d34e99df6dd5
  Author: William Tu <u9012063 at gmail.com>
  Date:   2020-03-23 (Mon, 23 Mar 2020)

  Changed paths:
    M include/openvswitch/vlog.h
    M lib/daemon-private.h
    M lib/daemon-unix.c
    M lib/fatal-signal.c
    M lib/vlog.c

  Log Message:
  fatal-signal: Log backtrace when no monitor daemon.

Currently the backtrace logging is only available when monitor
daemon is running.  This patch enables backtrace logging when
no monitor daemon exists.  At signal handling context, it detects
whether monitor daemon exists.  If not, write directly the backtrace
to the vlog fd.  Note that using VLOG_* macro doesn't work due to
it's buffer I/O, so this patch directly issue write() syscall to
the file descriptor.

For some system we stop using monitor daemon and use systemd to
monitor ovs-vswitchd, thus need this patch. Example of
ovs-vswitchd.log (note that there is no timestamp printed):
  2020-03-23T14:42:12.949Z|00049|memory|INFO|175332 kB peak resident
  2020-03-23T14:42:12.949Z|00050|memory|INFO|handlers:2 ports:3 reva
  SIGSEGV detected, backtrace:
  0x0000000000486969 <fatal_signal_handler+0x49>
  0x00007f7f5e57f4b0 <killpg+0x40>
  0x000000000047daa8 <pmd_thread_main+0x238>
  0x0000000000504edd <ovsthread_wrapper+0x7d>
  0x00007f7f5f0476ba <start_thread+0xca>
  0x00007f7f5e65141d <clone+0x6d>
  0x0000000000000000 <+0x0>

Acked-by: Ben Pfaff <blp at ovn.org>
Signed-off-by: William Tu <u9012063 at gmail.com>

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