lib: rewrite zlog lock-free & TLS-buffered

This is a full rewrite of the "back end" logging code.  It now uses a
lock-free list to iterate over logging targets, and the targets
themselves are as lock-free as possible.  (syslog() may have a hidden
internal mutex in the C library;  the file/fd targets use a single
write() call which should ensure atomicity kernel-side.)

Note that some functionality is lost in this patch:
- Solaris printstack() backtraces are ditched (unlikely to come back)
- the `log-filter` machinery is gone (re-added in followup commit)
- `terminal monitor` is temporarily stubbed out.  The old code had a
  race condition with VTYs going away.  It'll likely come back rewritten
  and with vtysh support.
- The `zebra_ext_log` hook is gone.  Instead, it's now much easier to
  add a "proper" logging target.

v2: TLS buffer to get some actual performance

Signed-off-by: David Lamparter <equinox@diac24.net>

1 files changed, 11 insertions, 17 deletions

diff --git a/configure.ac b/configure.ac
index 628e0c8af..f2343cc1b 100755
--- a/configure.ac
+++ b/configure.ac
@@ -959,7 +959,7 @@ int main(int argc, char **argv) {
 AC_CHECK_HEADERS([pthread_np.h],,, [
 #include <pthread.h>
 ])
-AC_CHECK_FUNCS([pthread_setname_np pthread_set_name_np])
+AC_CHECK_FUNCS([pthread_setname_np pthread_set_name_np pthread_getthreadid_np])
 
 needsync=true
 
@@ -1202,7 +1202,11 @@ dnl other functions
 dnl ---------------
 AC_CHECK_FUNCS([ \
 	strlcat strlcpy \
-	getgrouplist])
+	getgrouplist \
+	openat \
+	unlinkat \
+	posix_fallocate \
+	])
 
 dnl ##########################################################################
 dnl LARGE if block spans a lot of "configure"!
@@ -2197,22 +2201,12 @@ if test "$enable_backtrace" != "no" ; then
   fi
 
   if test "$backtrace_ok" = "no"; then
-    case "$host_os" in
-    sunos* | solaris2*)
-      AC_CHECK_FUNCS([printstack], [
-        AC_DEFINE([HAVE_PRINTSTACK], [1], [Solaris printstack])
+    AC_CHECK_HEADER([execinfo.h], [
+      AC_SEARCH_LIBS([backtrace], [execinfo], [
+        AC_DEFINE([HAVE_GLIBC_BACKTRACE], [1], [Glibc backtrace])
         backtrace_ok=yes
-      ])
-      ;;
-    esac
-    if test "$backtrace_ok" = "no"; then
-      AC_CHECK_HEADER([execinfo.h], [
-        AC_SEARCH_LIBS([backtrace], [execinfo], [
-          AC_DEFINE([HAVE_GLIBC_BACKTRACE], [1], [Glibc backtrace])
-          backtrace_ok=yes
-        ],, [-lm])
-      ])
-    fi
+      ],, [-lm])
+    ])
   fi
 
   if test "$enable_backtrace" = "yes" -a "$backtrace_ok" = "no"; then