[shepherd] 03/04: shepherd: In non-signalfd, fix dynamic state of signal handlers.

[Ludovic Courtès]

civodul pushed a commit to branch main
in repository shepherd.

commit 1ff1527641c7b0a34e3bd20ea12e2c48ab6b3885
Author: Ludovic Courtès <ludo@gnu.org>
AuthorDate: Sun Dec 24 12:10:23 2023 +0100

    shepherd: In non-signalfd, fix dynamic state of signal handlers.
    
    * modules/shepherd.scm (main): Move ‘sigaction’ calls for all of
    %PRECIOUS-SIGNALS under ‘unless signal-port’.  Wrap handler in
    ‘capture-dynamic-state’.
    * tests/signals.sh: Use ‘make-forkexec-constructor’ and ‘kill’.
---
 modules/shepherd.scm | 17 ++++++++---------
 tests/signals.sh     |  8 ++++++--
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/modules/shepherd.scm b/modules/shepherd.scm
index 9040ae1..6b22b22 100644
--- a/modules/shepherd.scm
+++ b/modules/shepherd.scm
@@ -450,12 +450,6 @@ fork in the child process."
           (false-if-exception
            (dynamic-link (string-append %pkglibdir "/crash-handler"))))
 
-        ;; Install signal handlers for everything but SIGCHLD, which is taken
-        ;; care of in (shepherd services).
-        (for-each (lambda (signal)
-                    (sigaction signal (signal-handler signal)))
-                  (delete SIGCHLD %precious-signals))
-
         ;; 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
@@ -467,11 +461,16 @@ fork in the child process."
                (register-services (list root-service))
                (start-service root-service)
 
-               ;; Install the SIGCHLD handler on systems that don't support
+               ;; Install signal handlers on systems that don't support
                ;; signalfd(2).  Capture the current dynamic state so that
-               ;; 'current-process-monitor' has the right value when the
-               ;; handler is invoked.
+               ;; 'current-process-monitor' & co. have the right value when
+               ;; the handler is invoked.
                (unless signal-port
+                 (for-each (lambda (signal)
+                             (sigaction signal
+                               (capture-dynamic-state (signal-handler 
signal))))
+                           (delete SIGCHLD %precious-signals))
+
                  (sigaction SIGCHLD (capture-dynamic-state handle-SIGCHLD)
                             SA_NOCLDSTOP))
 
diff --git a/tests/signals.sh b/tests/signals.sh
index 59fd183..5081b1c 100644
--- a/tests/signals.sh
+++ b/tests/signals.sh
@@ -36,8 +36,12 @@ cat > "$conf"<<EOF
 (register-services
  (list (service
         '(test)
-        #:start (const #t)
-        #:stop  (lambda _
+         ;; Use a real process to exhibit the scenario where
+         ;; the signal handler needs to send a message to
+         ;; the process monitor and/or service registry.
+        #:start (make-forkexec-constructor '("sleep" "100"))
+        #:stop  (lambda (pid)
+                   (kill pid SIGKILL)
                   (call-with-output-file "$stamp"
                     (lambda (port)
                       (display "stopped" port)))