Date: Sun, 10 Jan 1999 11:33:28 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Luoqi Chen <luoqi@watermarkgroup.com> Cc: dg@FreeBSD.ORG, syssgm@dtir.qld.gov.au, freebsd-current@FreeBSD.ORG Subject: Re: Hangs on "inode" and "thrd_sleep" Message-ID: <199901101933.LAA86598@apollo.backplane.com>
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:I ran into the same problem before. If you search the -current archive
:for deadlock, I posted a patch to solve this problem (I should have filed
:a PR for this). There are more serious problems with locking in vm_fault(),
:which are more difficult to fix, see PR 8416 by Tor Egge.
:
:-lq
:
:> My test machine hung last night during 'make -j5 buildworld' with 7 processes
:> in "thrd_sleep" and 2 in "inode". Thus began a marathon DDB session
:...
:>
Your patch to vm_fault.c in PR 8416 looks reasonable. If you have
an additional patch ( or is the one in PR8416 the one you 'posted' ??)
I'd appreciate it if you could email it to me.
In general, a lot of the confusion in the VM system stems from it
having to effectively bypass vm_object's and special-case vnode
related ops. What should really happen is that all VM ops should run
through the associated vm_object's and the backing store underlying
those objects should be hidden. Also, it should be possible to handle
other VM related deadlocks by locking-through to get a vm_page, lock the
page, and then hold the lock on the page while releasing all the other
locks. The PG_BUSY/vm_page->busy hacks could be used to effect here.
Fixing this would also solve the lock ordering problem. I'll put cleaning
this up on my list for 4.0.
-Matt
Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet
Communications & God knows what else.
<dillon@backplane.com> (Please include original email in any response)
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