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Re: [ jEdit-devel ] TokenMarker.java question
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From: Dale A. <da...@gr...> - 2009-10-03 15:13:36
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woops, just saw your other email about TaskList.
Wouldn't it be better to make TokenMarker reentrant rather than synchronized?
Dale
On Sat, Oct 3, 2009 at 9:08 AM, Dale Anson <da...@gr...> wrote:
> 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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>>>>>>>> https://lists.sourceforge.net/lists/listinfo/jedit-devel
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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