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authorLudovic Courtès <ludo@gnu.org>2020-04-17 12:45:54 +0200
committerLudovic Courtès <ludo@gnu.org>2020-04-17 23:18:32 +0200
commit10c413685f13af12fa2bb34796db82e1f52b47af (patch)
tree369ef536a3fabebf91802c5ea1d7b0e8d9adf7e6 /gnu/services/shepherd.scm
parent9d0b9c7c6c0b0d45653dea80b499314ea415d3c7 (diff)
services: Move 'user-processes' to (gnu services shepherd).
* gnu/services/base.scm (%do-not-kill-file) (user-processes-shepherd-service, user-processes-service-type): Move to... * gnu/services/shepherd.scm: ... here.
Diffstat (limited to 'gnu/services/shepherd.scm')
-rw-r--r--gnu/services/shepherd.scm126
1 files changed, 125 insertions, 1 deletions
diff --git a/gnu/services/shepherd.scm b/gnu/services/shepherd.scm
index 9906ae43c4..e99458da43 100644
--- a/gnu/services/shepherd.scm
+++ b/gnu/services/shepherd.scm
@@ -63,7 +63,9 @@
shepherd-service-lookup-procedure
shepherd-service-back-edges
- shepherd-service-upgrade))
+ shepherd-service-upgrade
+
+ user-processes-service-type))
;;; Commentary:
;;;
@@ -415,4 +417,126 @@ need to be restarted to complete their upgrade."
(values to-unload to-restart))
+
+;;;
+;;; User processes.
+;;;
+
+(define %do-not-kill-file
+ ;; Name of the file listing PIDs of processes that must survive when halting
+ ;; the system. Typical example is user-space file systems.
+ "/etc/shepherd/do-not-kill")
+
+(define (user-processes-shepherd-service requirements)
+ "Return the 'user-processes' Shepherd service with dependencies on
+REQUIREMENTS (a list of service names).
+
+This is a synchronization point used to make sure user processes and daemons
+get started only after crucial initial services have been started---file
+system mounts, etc. This is similar to the 'sysvinit' target in systemd."
+ (define grace-delay
+ ;; Delay after sending SIGTERM and before sending SIGKILL.
+ 4)
+
+ (list (shepherd-service
+ (documentation "When stopped, terminate all user processes.")
+ (provision '(user-processes))
+ (requirement requirements)
+ (start #~(const #t))
+ (stop #~(lambda _
+ (define (kill-except omit signal)
+ ;; Kill all the processes with SIGNAL except those listed
+ ;; in OMIT and the current process.
+ (let ((omit (cons (getpid) omit)))
+ (for-each (lambda (pid)
+ (unless (memv pid omit)
+ (false-if-exception
+ (kill pid signal))))
+ (processes))))
+
+ (define omitted-pids
+ ;; List of PIDs that must not be killed.
+ (if (file-exists? #$%do-not-kill-file)
+ (map string->number
+ (call-with-input-file #$%do-not-kill-file
+ (compose string-tokenize
+ (@ (ice-9 rdelim) read-string))))
+ '()))
+
+ (define (now)
+ (car (gettimeofday)))
+
+ (define (sleep* n)
+ ;; Really sleep N seconds.
+ ;; Work around <http://bugs.gnu.org/19581>.
+ (define start (now))
+ (let loop ((elapsed 0))
+ (when (> n elapsed)
+ (sleep (- n elapsed))
+ (loop (- (now) start)))))
+
+ (define lset= (@ (srfi srfi-1) lset=))
+
+ (display "sending all processes the TERM signal\n")
+
+ (if (null? omitted-pids)
+ (begin
+ ;; Easy: terminate all of them.
+ (kill -1 SIGTERM)
+ (sleep* #$grace-delay)
+ (kill -1 SIGKILL))
+ (begin
+ ;; Kill them all except OMITTED-PIDS. XXX: We would
+ ;; like to (kill -1 SIGSTOP) to get a fixed list of
+ ;; processes, like 'killall5' does, but that seems
+ ;; unreliable.
+ (kill-except omitted-pids SIGTERM)
+ (sleep* #$grace-delay)
+ (kill-except omitted-pids SIGKILL)
+ (delete-file #$%do-not-kill-file)))
+
+ (let wait ()
+ ;; Reap children, if any, so that we don't end up with
+ ;; zombies and enter an infinite loop.
+ (let reap-children ()
+ (define result
+ (false-if-exception
+ (waitpid WAIT_ANY (if (null? omitted-pids)
+ 0
+ WNOHANG))))
+
+ (when (and (pair? result)
+ (not (zero? (car result))))
+ (reap-children)))
+
+ (let ((pids (processes)))
+ (unless (lset= = pids (cons 1 omitted-pids))
+ (format #t "waiting for process termination\
+ (processes left: ~s)~%"
+ pids)
+ (sleep* 2)
+ (wait))))
+
+ (display "all processes have been terminated\n")
+ #f))
+ (respawn? #f))))
+
+(define user-processes-service-type
+ (service-type
+ (name 'user-processes)
+ (extensions (list (service-extension shepherd-root-service-type
+ user-processes-shepherd-service)))
+ (compose concatenate)
+ (extend append)
+
+ ;; The value is the list of Shepherd services 'user-processes' depends on.
+ ;; Extensions can add new services to this list.
+ (default-value '())
+
+ (description "The @code{user-processes} service is responsible for
+terminating all the processes so that the root file system can be re-mounted
+read-only, just before rebooting/halting. Processes still running after a few
+seconds after @code{SIGTERM} has been sent are terminated with
+@code{SIGKILL}.")))
+
;;; shepherd.scm ends here