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authorLudovic Courtès <ludo@gnu.org>2014-05-14 16:38:21 +0200
committerLudovic Courtès <ludo@gnu.org>2014-05-14 19:07:03 +0200
commit7d57cfd3b6625d7ab7f796b90b9606c28ec3aeef (patch)
treecfc0f210efc75d159fdcb543dd45f0c106095c35
parent17a4d344899dca6a429fc79bc3b54edbe5079956 (diff)
downloadguix-7d57cfd3b6625d7ab7f796b90b9606c28ec3aeef.tar
guix-7d57cfd3b6625d7ab7f796b90b9606c28ec3aeef.tar.gz
system: When unionfs-fuse is used for /, don't kill it when halting.
* guix/build/linux-initrd.scm (pidof): New procedure. (mount-root-file-system)[mark-as-not-killable]: New procedure. Use it for unionfs when VOLATILE-ROOT?. * gnu/services/base.scm (%do-not-kill-file): New variable. (user-processes-service)[stop]: Honor it.
-rw-r--r--gnu/services/base.scm42
-rw-r--r--guix/build/linux-initrd.scm26
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))))