From: "Peter Graf" <p.graf@itknet.de>
To: <ecos-discuss@ecos.sourceware.org>
Subject: [ECOS] Massive ISR to DSR delay caused by free()
Date: Tue, 03 Dec 2013 10:19:00 -0000 [thread overview]
Message-ID: <529DBE350200007E0000ABD9@Groupware> (raw)
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
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next reply other threads:[~2013-12-03 10:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-03 10:19 Peter Graf [this message]
2013-12-03 13:37 ` Bernd Edlinger
2013-12-03 15:36 ` Antw: " Peter Graf
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