From: "Peter Graf" <p.graf@itknet.de>
To: "ecos-discuss@ecos.sourceware.org" <ecos-discuss@ecos.sourceware.org>
Subject: Antw: RE: [ECOS] Massive ISR to DSR delay caused by free()
Date: Tue, 03 Dec 2013 15:36:00 -0000 [thread overview]
Message-ID: <529E088D0200007E0000ABE5@Groupware> (raw)
In-Reply-To: <DUB122-W523DBD494B0C708798E81AE4D50@phx.gbl>
Thanks Bernd,
I already tried the latest dlmalloc.cxx earlier, but apparently the simple variable block implementation is used. Do you know in general, wether a DSR gets delayed if free() is called from a thread?
Kind regards,
Peter
>>> Bernd Edlinger <bernd.edlinger@hotmail.de> schrieb am Dienstag, 3. Dezember
2013 um 14:37 in Nachricht <DUB122-W523DBD494B0C708798E81AE4D50@phx.gbl>:
> On Tue, 3 Dec 2013 11:19:17, Peter Graf wrote:
>>
>> Hi,
>>
>> under rare circumstances, we experienced a massive timing overflow of a
> cyclical DSR. It turned out to be an issue with JFFS2, occurring after a
> system reboot if long files had been written to the filesystem before.
>>
>> I found that the issue was only caused by JFFS2's
>>
>> malloc-ecos.c: jffs2_free_full_dnode()
>>
>> By using an oscilloscope, I could see that after the ISR was served, the DSR
> was delayed, just because free() was called by jffs2_free_full_dnode(). More
> precisely, the CPU time was spent in memalloc's
>>
>> mvarimpl.inl: Cyg_Mempool_Variable_Implementation::insert_free_block()
>>
>> At first I thought it was a locking issue within JFFS2. But in the end I
> could not see any scheduler locks which might have caused it.
>>
>> I now have indications, that it could be a general issue with free(). A call
> to free() from even a low priority thread seems to delay DSR execution after
> the ISR!
>>
>> The allocator is compiled to be thread-safe, but in my opinion it would be a
> major drawback if even a low priority thread could not call free() without
> delaying a critical DSR.
>>
>> Can someone confirm this behaviour? Is it intended?
>>
>> Many thanks,
>> Peter
>>
>>
>>
>>
>> --
>> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
>> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
>>
>
> This sounds like a know deficiency of the very first Doug-Lee Malloc.
>
> Maybe you want check if this patch works for you?
>
> http://bugs.ecos.sourceware.org/show_bug.cgi?id=1001634
>
>
> Regards
> Bernd Edlinger.
> --
> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
prev parent reply other threads:[~2013-12-03 15:36 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-03 10:19 Peter Graf
2013-12-03 13:37 ` Bernd Edlinger
2013-12-03 15:36 ` Peter Graf [this message]
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