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Re: [ jEdit-devel ] TokenMarker.java question
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From: Dale A. <da...@gr...> - 2009-10-03 15:09:06
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What was the issue with TaskList? And which TaskList -- the one in
PluginManager or the one from Eric's daily builds?
Dale
On Sat, Oct 3, 2009 at 7:39 AM, Shlomy Reinstein <sre...@gm...> wrote:
> I have committed this small change (make TokenMarker.markTokens
> synchronized) and it seems to solve the issue with TaskList.
> I also haven't noticed any performance impact of this. If anyone
> discovers a performance problem caused by this, let me know and I'll
> fix it.
>
> Shlomy
>
> On Sat, Oct 3, 2009 at 11:40 AM, Shlomy Reinstein <sre...@gm...> wrote:
>> Hi,
>>
>> It turns out that TokenMarker.markTokens is not thread-safe. It needs
>> to be synchronized. It has a 'context' field, that is potentially
>> updated each time "markTokens" is called. If called simultaneously by
>> multiple threads, each may modify it, causing the other threads to use
>> an incorrect context.
>>
>> I just verified that the problem happens very frequently with the
>> TaskList plugin. TaskList has a dockable which shows the tasks in the
>> current buffer, and also highlights tasks in the text area. To find
>> the tasks in the buffer, it uses "markTokens" in the background. So,
>> when this plugin is in use, I experience all kinds of painting issues
>> and occasionally the NPE that Dale experienced.
>> Disabling the TaskList plugin gets rid of all these problems.
>>
>> However, it is not a TaskList problem, "markTokens" simply needs to be
>> synchronized. If this causes some performance problem in the core,
>> then we should have two separate paths to markTokens, one for the core
>> and one for plugins, and make the plugin's path ensure thread-safety,
>> e.g. by deferring the task to the AWT thread.
>>
>> Shlomy
>>
>> On Sat, Oct 3, 2009 at 3:39 AM, Dale Anson <da...@gr...> wrote:
>>> Actually, I verified that context.parent is occasionally null, which
>>> causes the NPE when its 'rules' field is referenced. Thinking about
>>> this some more, I bet is it's a threading issue. It could be that in
>>> the first check (in the code you sent) it is not null, but is reset to
>>> null before the method is actually invoked. That would mean my patch
>>> is not very good since it doesn't address thread-safety.
>>>
>>> I did double check, I've got source for jEdit at revision 16233. The
>>> only change I have is the one I made to this class. I verified that
>>> I'm using the standard java mode from svn also, and it's while editing
>>> java files that I know I've seen the problem. I'm not sure if I've
>>> seen this issue in other modes.
>>>
>>> Dale
>>>
>>>
>>> On Fri, Oct 2, 2009 at 2:46 AM, Shlomy Reinstein <sre...@gm...> wrote:
>>>> I took a more thorough look at the code. It is absolutely IMPOSSIBLE
>>>> that context.parent is null in the method that generates the NPE for
>>>> you, unless you've changed something in the jedit core. There is only
>>>> one place where the method generating the NPE is called:
>>>> //{{{ check for end of delegate
>>>> if (context.parent != null
>>>> && context.parent.inRule != null
>>>> && checkDelegateEnd(context.parent.inRule))
>>>> {
>>>> seenWhitespaceEnd = true;
>>>> continue main_loop;
>>>> } //}}}
>>>>
>>>> Note the check for "context.parent" not being null before calling this method.
>>>> An NPE can still be caused by this line, but it won't be for
>>>> "context.parent" being null, rather it would be for
>>>> "context.parent.rules" being null.
>>>>
>>>> Shlomy
>>>>
>>>> On Fri, Oct 2, 2009 at 8:15 AM, Dale Anson <da...@gr...> wrote:
>>>>> No, I can't reproduce it reliably. Somehow, I get into this state
>>>>> after a couple of hours of running jEdit. Usually, it happens when
>>>>> I'm editing somewhere in the middle of a file, I'll hit Enter at the
>>>>> end of a line to start the next line and then there is the trouble. I
>>>>> have verified that it is definitely the case that context.parent is
>>>>> sometimes null. I see in LineContext itself that there are a several
>>>>> checks for a null parent, but not elsewhere. I think I've only seen
>>>>> this with java files, but I'm not absolutely certain.
>>>>>
>>>>> Do you know of a better thing to do if context.parent is null?
>>>>>
>>>>> Dale
>>>>>
>>>>>
>>>>> On Thu, Oct 1, 2009 at 11:31 PM, Shlomy Reinstein <sre...@gm...> wrote:
>>>>>> Hi,
>>>>>> Can you reproduce this every time with some example?
>>>>>> If not , does this happen when you are editing (i.e. pressing enter
>>>>>> on) the first or second line, or also when editing subsequent lines
>>>>>> down the file?
>>>>>> The 'parent' is usually the LineContext of the previous line.
>>>>>> Shlomy
>>>>>>
>>>>>> On Fri, Oct 2, 2009 at 3:33 AM, Dale Anson <da...@gr...> wrote:
>>>>>>> I entered a patch to fix this, see tracker 2871624. I did some more
>>>>>>> investigation, and it turns out that context.parent can be null. The
>>>>>>> patch checks for this case, and if the parent is null, it just
>>>>>>> continues to use the same context. So far, this seems to be working
>>>>>>> fine.
>>>>>>>
>>>>>>> Dale
>>>>>>>
>>>>>>>
>>>>>>> On Wed, Sep 30, 2009 at 1:07 PM, Alan Ezust <ala...@gm...> wrote:
>>>>>>>> I've seen an NPE there from time to time also, but I can't reproduce it.
>>>>>>>>
>>>>>>>> On Wed, Sep 30, 2009 at 11:50 AM, Dale Anson <da...@gr...> wrote:
>>>>>>>>>
>>>>>>>>> On Wed, Sep 30, 2009 at 9:58 AM, Matthieu Casanova
>>>>>>>>> <cho...@gm...> wrote:
>>>>>>>>> > But in that code, the fields are used as parameters, so filling the
>>>>>>>>> > keyword
>>>>>>>>> > field at line 294 is used to highlight tokens, removing that will lead
>>>>>>>>> > to
>>>>>>>>> > bugs.
>>>>>>>>> > For the NPE at line 294, do you know if it is because of context being
>>>>>>>>> > null
>>>>>>>>> > or context.rules ?
>>>>>>>>>
>>>>>>>>> I don't know. I didn't look into it far enough. I supposed, though,
>>>>>>>>> if I'm the only one seeing this issue, that means I've got something
>>>>>>>>> wrong somewhere.
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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