Date: Mon, 7 Jun 1999 01:00:25 -0500 (EST) From: "John S. Dyson" <dyson@iquest.net> To: adsharma@home.com (Arun Sharma) Cc: green@unixhelp.org (Brian Feldman), hackers@FreeBSD.ORG Subject: Re: problem for the VM gurus Message-ID: <199906070600.BAA63817@dyson.iquest.net.> In-Reply-To: <m3emjoem7w.fsf@c62443-a.frmt1.sfba.home.com> from Arun Sharma at "Jun 6, 1999 08:14:11 pm"
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Arun Sharma said: > bread > ffs_read > ffs_getpages > vnode_pager_getpages > vm_fault > --- > slow_copyin > ffs_write > vn_write > dofilewrite > write > syscall > > getblk finds that the buffer is marked B_BUSY and sleeps on it. But I > can't figure out who marked it busy. > This looks like the historical problem of doing I/O to an mmap'ed region. There are two facets to the problem: One where the I/O is to the same vn, and the other is where the I/O is to a different vn. The case where the I/O is to the same vn had a (short term) fix previously in the code, by allowing for recursive usage of a vn under certain circumstances. The problem of different vn's can be fixed by proper resource handling in vfs_bio (and perhaps other places.) (My memory isn't 100% clear on the code anymore, but you have shown alot of info with your backtrace.) -- John | Never try to teach a pig to sing, dyson@iquest.net | it makes one look stupid jdyson@nc.com | and it irritates the pig. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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