Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.java.programmer > #35520
| From | j4n bur53 <janburse@fastmail.fm> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: I dont see a deadlock (Re: Library for Escalable Locks, Slimmest API?) |
| Date | 2016-08-31 14:13 +0200 |
| Organization | albasani.net |
| Message-ID | <nq6hm1$2it$1@news.albasani.net> (permalink) |
| References | <no7p5p$11i$1@news.albasani.net> <nq54i4$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> |
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();
In my case I have invalidation by another thread.
See also my answer to Andreas Leitgeb.
Eric Sosman schrieb:
> On 8/30/2016 7:45 PM, bursejan@gmail.com wrote:
>> My example is rather:
>>
>> if (cache[idx] == null)
>> cache[idx] = new Cache(idx)
>>
>> And new Cache(idx) is expensive, and it can
>> happen that a large number of threads choose
>> the same idx
>
> Even if new Cache(idx) is cheap, there might be trouble
> if different threads use different Cache instances instead
> of sharing just one.
>
>> What should be done?
>
> synchronized(cache) {
> if (cache[idx] == null)
> cache[idx] = new Cache(idx);
> }
> cache[idx].useTheCache();
>
> Fancier schemes exist, but I would suggest you not bother with
> them until and unless the above simple approach proves inadequate.
> If actual measurement shows that you need something else, *then*
> it will be time to consider alternatives.
>
Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
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
csiph-web