Subject: bug#45314: closed (Re: bug#45314: ‘guix discover’ polls)

From: [email-masked] (GNU bug Tracking System)
Date: Sun, 20 Dec 2020 09:44:01 +0000

Your bug report

#45314: ‘guix discover’ polls

which was filed against the guix package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
45314: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=45314
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#45314: ‘guix discover’ polls
From: Mathieu Othacehe <[email-masked]>
To: Ludovic Courtès <[email-masked]>
Cc: [email-masked]
Date: Sun, 20 Dec 2020 10:43:00 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Hey Ludo,

> How about the change below?

I think it looks nice! I pushed it as
f9978346e73359ac1d8b88c9ed874edc7225582b.

Thanks,

Mathieu

Subject: ‘guix discover’ polls
From: Ludovic Courtès <[email-masked]>
To: [email-masked]
Date: Fri, 18 Dec 2020 18:10:04 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi!

‘guix discover’ polls with 100ms intervals:

--8<---------------cut here---------------start------------->8---
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:57 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:57 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:57 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:57 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:57 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:57 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:57 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
18:00:58 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
18:00:58 poll([{fd=14, events=POLLIN}, {fd=16, events=POLLIN}], 2, 100) = 0 (Timeout)
--8<---------------cut here---------------end--------------->8---

This comes from ‘avahi-browse-service-thread’ in (guix avahi) and its
100ms #:timeout.

How about the change below?

Thanks,
Ludo’.

diff --git a/guix/avahi.scm b/guix/avahi.scm
index aa90a5cdd4..132e42f268 100644
--- a/guix/avahi.scm
+++ b/guix/avahi.scm
@@ -89,13 +89,19 @@ when STOP-LOOP? procedure returns true."
     (close-port socket)
     ip))
 
+(define never
+  ;; Never true.
+  (const #f))
+
 (define* (avahi-browse-service-thread proc
                                       #:key
                                       types
                                       (ignore-local? #t)
                                       (family AF_INET)
-                                      (stop-loop? (const #f))
-                                      (timeout 100))
+                                      (stop-loop? never)
+                                      (timeout (if (eq? stop-loop? never)
+                                                   #f
+                                                   100)))
   "Browse services which type is part of the TYPES list, using Avahi.  The
 search is restricted to services with the given FAMILY.  Each time a service
 is found or removed, PROC is called and passed as argument the corresponding
@@ -167,4 +173,6 @@ when STOP-LOOP? procedure returns true."
                               client-callback)))
     (and (client? client)
          (while (not (stop-loop?))
-           (iterate-simple-poll poll timeout)))))
+           (if timeout
+               (iterate-simple-poll poll timeout)
+               (iterate-simple-poll poll))))))