civodul pushed a commit to branch wip-fibers
in repository shepherd.
commit 4c7a857827d3e279232bf1378d6c83791e8934ac
Author: Ludovic Courtès <l...@gnu.org>
AuthorDate: Mon Mar 21 10:20:23 2022 +0100
Use Fibers.
* configure.ac: Add 'GUILE_MODULE_AVAILABLE' use for Fibers.
Add 'AC_CACHE_CHECK' use for 'ac_cv_fibers_creates_pthreads'.
* modules/shepherd.scm: Use (fibers).
(signal-handler): In the SIGTERM/SIGHUP case, catch 'quit.
(main): Wrap call to 'run-daemon' in 'run-fibers'.
(quit-exception-handler): Call 'primitive-exit' in the default case.
---
configure.ac | 25 +++++++++++++++++++++++++
modules/shepherd.scm | 29 +++++++++++++++++++++--------
2 files changed, 46 insertions(+), 8 deletions(-)
diff --git a/configure.ac b/configure.ac
index ac6493d..f98dbb4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -33,6 +33,31 @@
guileobjectdir="${libdir}/guile/$GUILE_EFFECTIVE_VERSION/site-ccache"
AC_SUBST([guilemoduledir])
AC_SUBST([guileobjectdir])
+dnl Check for extra dependencies.
+GUILE_MODULE_AVAILABLE([have_fibers], [(fibers)])
+if test "x$have_fibers" != "xyes"; then
+ AC_MSG_ERROR([Fibers is missing; please install it.])
+fi
+
+dnl Make sure Fibers does not create POSIX threads: since shepherd
+dnl forks, it must be single-threaded.
+AC_CACHE_CHECK([whether Fibers might create POSIX threads],
+ [ac_cv_fibers_creates_pthreads],
+ [GUILE_CHECK([retval],
+ [(use-modules (fibers))
+ (set! (@ (ice-9 threads) call-with-new-thread)
+ (lambda _ (throw 'new-thread!)))
+ (run-fibers (lambda () (spawn-fiber (lambda () 1)))
+ #:parallelism 1 #:hz 0)])
+ if test "$retval" = 0; then
+ ac_cv_fibers_creates_pthreads="no"
+ else
+ ac_cv_fibers_creates_pthreads="yes"
+ fi])
+if test "x$ac_cv_fibers_creates_pthreads" = "xyes"; then
+ AC_MSG_ERROR([Fibers creates POSIX threads behind our back; aborting.])
+fi
+
dnl
dnl Low-level operating system interface.
dnl
diff --git a/modules/shepherd.scm b/modules/shepherd.scm
index 4365ca8..da2e509 100644
--- a/modules/shepherd.scm
+++ b/modules/shepherd.scm
@@ -20,6 +20,7 @@
;; along with the GNU Shepherd. If not, see <http://www.gnu.org/licenses/>.
(define-module (shepherd)
+ #:use-module (fibers)
#:use-module (ice-9 match)
#:use-module (ice-9 format)
#:use-module (ice-9 rdelim) ;; Line-based I/O.
@@ -107,7 +108,11 @@ already ~a threads running, disabling 'signalfd' support")
((= signal SIGINT)
(lambda _ (handle-SIGINT)))
((memv signal (list SIGTERM SIGHUP))
- (lambda _ (stop root-service)))
+ (lambda _
+ (catch 'quit
+ (lambda ()
+ (stop root-service))
+ quit-exception-handler)))
(else
(const #f))))
@@ -366,12 +371,18 @@ already ~a threads running, disabling 'signalfd' support")
(sigaction signal (signal-handler signal)))
(delete SIGCHLD %precious-signals))
- (run-daemon #:socket-file socket-file
- #:config-file config-file
- #:pid-file pid-file
- #:signal-port signal-port
- #:poll-services? poll-services?
- #:persistency persistency))))
+ ;; Run Fibers in such a way that it does not create any POSIX thread,
+ ;; because POSIX threads and 'fork' cannot be used together.
+ (run-fibers
+ (lambda ()
+ (run-daemon #:socket-file socket-file
+ #:config-file config-file
+ #:pid-file pid-file
+ #:signal-port signal-port
+ #:poll-services? poll-services?
+ #:persistency persistency))
+ #:parallelism 1 ;don't create POSIX threads
+ #:hz 0)))) ;disable preemption, which would require POSIX threads
;; Start all of SERVICES, which is a list of canonical names (FIXME?),
;; but in a order where all dependencies are fulfilled before we
@@ -420,7 +431,9 @@ already ~a threads running, disabling 'signalfd' support")
(begin
(local-output (l10n "Rebooting..."))
(reboot))
- (quit)))
+ (begin
+ (local-output (l10n "Exiting."))
+ (primitive-exit 0)))) ;leave without going through Fibers
(define (process-command command port)
"Interpret COMMAND, a command sent by the user, represented as a
