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offload: Remove unnecessary locking on machine slots.

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This extra level of locking turned out to be unnecessary.

* guix/scripts/offload.scm (with-machine-lock): Remove.
(machine-lock-file): Remove.
(acquire-build-slot): Remove surrounding 'with-machine-lock'.
This commit is contained in:
Ludovic Courtès 2018-12-26 17:42:02 +01:00
parent 7f4d102c2f
commit 0ef595b996
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GPG key ID: 090B11993D9AEBB5
1 changed files with 19 additions and 31 deletions
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50
guix/scripts/offload.scm
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@ -260,13 +260,6 @@ (define-syntax-rule (with-file-lock file exp ...)
(lambda ()
(unlock-file port)))))
(define-syntax-rule (with-machine-lock machine hint exp ...)
"Wait to acquire MACHINE's exclusive lock for HINT, and evaluate EXP in that
context."
(with-file-lock (machine-lock-file machine hint)
exp ...))
(define (machine-slot-file machine slot)
"Return the file name of MACHINE's file for SLOT."
;; For each machine we have a bunch of files representing each build slot.
@ -284,23 +277,25 @@ (define (acquire-build-slot machine)
This mechanism allows us to set a hard limit on the number of simultaneous
connections allowed to MACHINE."
(mkdir-p (dirname (machine-slot-file machine 0)))
(with-machine-lock machine 'slots
(any (lambda (slot)
(let ((port (open-file (machine-slot-file machine slot)
"w0")))
(catch 'flock-error
(lambda ()
(fcntl-flock port 'write-lock #:wait? #f)
;; Got it!
(format (current-error-port)
"process ~a acquired build slot '~a'~%"
(getpid) (port-filename port))
port)
(lambda args
;; PORT is already locked by another process.
(close-port port)
#f))))
(iota (build-machine-parallel-builds machine)))))
;; When several 'guix offload' processes run in parallel, there's a race
;; among them, but since they try the slots in the same order, we're fine.
(any (lambda (slot)
(let ((port (open-file (machine-slot-file machine slot)
"w0")))
(catch 'flock-error
(lambda ()
(fcntl-flock port 'write-lock #:wait? #f)
;; Got it!
(format (current-error-port)
"process ~a acquired build slot '~a'~%"
(getpid) (port-filename port))
port)
(lambda args
;; PORT is already locked by another process.
(close-port port)
#f))))
(iota (build-machine-parallel-builds machine))))
(define (release-build-slot slot)
"Release SLOT, a build slot as returned as by 'acquire-build-slot'."
@ -447,12 +442,6 @@ (define (normalized-load machine load)
normalized)
load))
(define (machine-lock-file machine hint)
"Return the name of MACHINE's lock file for HINT."
(string-append %state-directory "/offload/"
(build-machine-name machine)
"." (symbol->string hint) ".lock"))
(define (random-seed)
(logxor (getpid) (car (gettimeofday))))
@ -827,7 +816,6 @@ (define not-coma
(leave (G_ "invalid arguments: ~{~s ~}~%") x))))
;;; Local Variables:
;;; eval: (put 'with-machine-lock 'scheme-indent-function 2)
;;; eval: (put 'with-file-lock 'scheme-indent-function 1)
;;; eval: (put 'with-error-to-port 'scheme-indent-function 1)
;;; eval: (put 'with-timeout 'scheme-indent-function 2)