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Groups > comp.lang.java.programmer > #35525
| From | Eric Sosman <esosman@comcast-dot-net.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) |
| Date | 2016-08-31 12:55 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <nq725j$jg2$1@dont-email.me> (permalink) |
| References | (1 earlier) <nq54i4$eob$1@news.albasani.net> <b5cbcac6-a402-4bf2-aace-9e181c3e0bd4@googlegroups.com> <26083865-8e3e-4fb5-9767-4d638ade4b6f@googlegroups.com> <nq6g8s$kba$1@dont-email.me> <nq6hm1$2it$1@news.albasani.net> |
On 8/31/2016 8:13 AM, j4n bur53 wrote:
> If cache[idx] can be invalidated by another thread
> by setting cache[idx]=null then your code is wrong.
>
>> synchronized(lock) {
>> if (caches[idx] == null)
>> caches[idx] = new Cache(idx);
>> }
> /* here is a problem other thread could interfer */
>> caches[idx].useTheCache();
>
> After the synchronized block you might get a null
> pointer error. Correct code would be:
>
> Cache cache;
> synchronized(lock) {
> cache = caches[idx];
> if (cache == null)
> cache = new Cache(idx);
> caches[idx] = cache.
> }
> }
> cache.useTheCache();
Okay; your post didn't mention nulling of caches[] elements
as a consideration. (Note that if another thread sets "caches"
itself to null -- or "lock" or "idx", for that matter -- both
code versions are in trouble.)
> In my case I have invalidation by another thread.
This seems a peculiar way to invalidate a cache. Observe that
even after thread T1 sets caches[idx] = null, threads T2,T3,...
may still be using the old, stale Cache instance. Normally, one
would have a cache.invalidate() method, or something like it: Keep
the Cache object, but tell it to adjust its own state.
--
esosman@comcast-dot-net.invalid
The Tooth Fairy has gone high-tech, now pays in Bitecoin.
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Library for Escalable Locks, Slimmest API? Jan Burse <janburse@fastmail.fm> - 2016-08-07 18:55 +0200
Re: Library for Escalable Locks, Slimmest API? Andreas Leitgeb <avl@logic.at> - 2016-08-08 01:10 +0000
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-08 09:38 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-08 09:47 +0200
Re: Library for Escalable Locks, Slimmest API? Andreas Leitgeb <avl@logic.at> - 2016-08-10 14:39 +0000
Re: Library for Escalable Locks, Slimmest API? Jan Burse <janburse@fastmail.fm> - 2016-08-10 18:05 +0200
Re: Library for Escalable Locks, Slimmest API? Lew <lewbloch@gmail.com> - 2016-08-10 17:44 -0700
Re: Library for Escalable Locks, Slimmest API? Jan Burse <janburse@fastmail.fm> - 2016-08-11 12:43 +0200
Re: Library for Escalable Locks, Slimmest API? Robert Klemme <shortcutter@googlemail.com> - 2016-08-12 22:18 +0200
Re: Library for Escalable Locks, Slimmest API? Andreas Leitgeb <avl@logic.at> - 2016-08-13 05:56 +0000
Re: Library for Escalable Locks, Slimmest API? Robert Klemme <shortcutter@googlemail.com> - 2016-08-13 11:08 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-13 11:37 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-13 11:39 +0200
Re: Library for Escalable Locks, Slimmest API? Jan Burse <janburse@fastmail.fm> - 2016-08-13 12:27 +0200
Re: Library for Escalable Locks, Slimmest API? Robert Klemme <shortcutter@googlemail.com> - 2016-08-13 23:21 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 11:42 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 11:50 +0200
Jumping to false Conclusions [Robert Klemme] (Was: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-14 12:06 +0200
Re: Jumping to false Conclusions [Robert Klemme] (Was: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-14 13:08 +0200
Re: Jumping to false Conclusions [Robert Klemme] (Was: Library for Escalable Locks, Slimmest API?) Robert Klemme <shortcutter@googlemail.com> - 2016-08-14 13:45 +0200
Re: Jumping to false Conclusions [Robert Klemme] (Was: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-14 14:01 +0200
Re: Jumping to false Conclusions [Robert Klemme] (Was: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-14 14:01 +0200
Re: Jumping to false Conclusions [Robert Klemme] (Was: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-14 14:07 +0200
Re: Library for Escalable Locks, Slimmest API? Robert Klemme <shortcutter@googlemail.com> - 2016-08-14 12:13 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 12:25 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 12:36 +0200
Re: Library for Escalable Locks, Slimmest API? Robert Klemme <shortcutter@googlemail.com> - 2016-08-14 13:41 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 12:45 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 12:49 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 13:45 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 13:48 +0200
Re: Library for Escalable Locks, Slimmest API? Robert Klemme <shortcutter@googlemail.com> - 2016-08-14 14:29 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 14:56 +0200
Re: Library for Escalable Locks, Slimmest API? j4n bur53 <janburse@fastmail.fm> - 2016-08-14 14:59 +0200
Re: Library for Escalable Locks, Slimmest API? Jan Burse <janburse@fastmail.fm> - 2016-08-14 18:10 +0200
Simpler requirements on the horizon! (Re: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-14 13:18 +0200
I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-31 01:23 +0200
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) bursejan@gmail.com - 2016-08-30 16:35 -0700
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) bursejan@gmail.com - 2016-08-30 16:45 -0700
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) Andreas Leitgeb <avl@logic.at> - 2016-08-31 09:23 +0000
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) Andreas Leitgeb <avl@logic.at> - 2016-08-31 10:13 +0000
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-31 14:00 +0200
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-31 07:49 -0400
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) j4n bur53 <janburse@fastmail.fm> - 2016-08-31 14:13 +0200
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-31 12:55 -0400
Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-08-31 07:54 -0400
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