diff options
| -rw-r--r-- | gnu/services/base.scm | 42 | ||||
| -rw-r--r-- | guix/build/linux-initrd.scm | 26 |
2 files changed, 64 insertions, 4 deletions
diff --git a/gnu/services/base.scm b/gnu/services/base.scm index 1f5ff3e4cb..aec6050588 100644 --- a/gnu/services/base.scm +++ b/gnu/services/base.scm @@ -110,6 +110,11 @@ OPTIONS. When CHECK? is true, check the file system before mounting it." (umount #$target) #f)))))) +(define %do-not-kill-file + ;; Name of the file listing PIDs of processes that must survive when halting + ;; the system. Typical example is user-space file systems. + "/etc/dmd/do-not-kill") + (define* (user-processes-service requirements #:key (grace-delay 2)) "Return the service that is responsible for terminating all the processes so that the root file system can be re-mounted read-only, just before @@ -128,6 +133,25 @@ stopped before 'kill' is called." (requirement (cons 'root-file-system requirements)) (start #~(const #t)) (stop #~(lambda _ + (define (kill-except omit signal) + ;; Kill all the processes with SIGNAL except those + ;; listed in OMIT and the current process. + (let ((omit (cons (getpid) omit))) + (for-each (lambda (pid) + (unless (memv pid omit) + (false-if-exception + (kill pid signal)))) + (processes)))) + + (define omitted-pids + ;; List of PIDs that must not be killed. + (if (file-exists? #$%do-not-kill-file) + (map string->number + (call-with-input-file #$%do-not-kill-file + (compose string-tokenize + (@ (ice-9 rdelim) read-string)))) + '())) + ;; When this happens, all the processes have been ;; killed, including 'deco', so DMD-OUTPUT-PORT and ;; thus CURRENT-OUTPUT-PORT are dangling. @@ -136,9 +160,21 @@ stopped before 'kill' is called." (display "sending all processes the TERM signal\n" port))) - (kill -1 SIGTERM) - (sleep #$grace-delay) - (kill -1 SIGKILL) + (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))) (display "all processes have been terminated\n") #f)) diff --git a/guix/build/linux-initrd.scm b/guix/build/linux-initrd.scm index 0c3b2f0d9f..b488668ee2 100644 --- a/guix/build/linux-initrd.scm +++ b/guix/build/linux-initrd.scm @@ -200,11 +200,30 @@ networking values.) Return #t if INTERFACE is up, #f otherwise." the last argument of `mknod'." (+ (* major 256) minor)) +(define (pidof program) + "Return the PID of the first presumed instance of PROGRAM." + (let ((program (basename program))) + (find (lambda (pid) + (let ((exe (format #f "/proc/~a/exe" pid))) + (and=> (false-if-exception (readlink exe)) + (compose (cut string=? program <>) basename)))) + (filter-map string->number (scandir "/proc"))))) + (define* (mount-root-file-system root type #:key volatile-root? (unionfs "unionfs")) "Mount the root file system of type TYPE at device ROOT. If VOLATILE-ROOT? is true, mount ROOT read-only and make it a union with a writable tmpfs using UNIONFS." + (define (mark-as-not-killable pid) + ;; Tell the 'user-processes' dmd service that PID must be kept alive when + ;; shutting down. + (mkdir-p "/root/etc/dmd") + (let ((port (open-file "/root/etc/dmd/do-not-kill" "a"))) + (chmod port #o600) + (write pid port) + (newline port) + (close-port port))) + (catch #t (lambda () (if volatile-root? @@ -222,7 +241,12 @@ UNIONFS." "cow,allow_other,use_ino,suid,dev" "/rw-root=RW:/real-root=RO" "/root")) - (error "unionfs failed"))) + (error "unionfs failed")) + + ;; Make sure unionfs remains alive till the end. Because + ;; 'fuse_daemonize' doesn't tell the PID of the forked daemon, we + ;; have to resort to 'pidof' here. + (mark-as-not-killable (pidof unionfs))) (begin (check-file-system root type) (mount root "/root" type)))) |