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[PATCH] Futures: Avoid creating the worker pool more than once
From: |
Mark H Weaver |
Subject: |
[PATCH] Futures: Avoid creating the worker pool more than once |
Date: |
Tue, 06 Nov 2012 18:07:35 -0500 |
Any objections to applying this fix?
Mark
>From ff2c84b118b68020805eae93f71c3a8fd13ca3d9 Mon Sep 17 00:00:00 2001
From: Mark H Weaver <address@hidden>
Date: Tue, 6 Nov 2012 18:03:39 -0500
Subject: [PATCH] Futures: Avoid creating the worker pool more than once.
* module/ice-9/futures.scm (%create-workers!): Check to make sure the
worker pool hasn't already been created within the critical section.
---
module/ice-9/futures.scm | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/module/ice-9/futures.scm b/module/ice-9/futures.scm
index 0f64b5c..afdf48f 100644
--- a/module/ice-9/futures.scm
+++ b/module/ice-9/futures.scm
@@ -158,13 +158,19 @@ touched."
(define (%create-workers!)
(lock-mutex %futures-mutex)
- (set! %workers
- (unfold (lambda (i) (>= i %worker-count))
- (lambda (i)
- (call-with-new-thread process-futures))
- 1+
- 0))
- (set! create-workers! (lambda () #t))
+ ;; setting 'create-workers!' to a no-op is an optimization, but it is
+ ;; still possible for '%create-workers!' to be called more than once
+ ;; from different threads. Therefore, to avoid creating %workers more
+ ;; than once (and thus creating too many threads), we check to make
+ ;; sure %workers is empty within the critical section.
+ (when (null? %workers)
+ (set! create-workers! (lambda () #t))
+ (set! %workers
+ (unfold (lambda (i) (>= i %worker-count))
+ (lambda (i)
+ (call-with-new-thread process-futures))
+ 1+
+ 0)))
(unlock-mutex %futures-mutex))
(define create-workers!
--
1.7.10.4