From: "M. Edward Borasky" <znmeb@cesmail.net>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Negative "ios_in_flight" in the 2.4 kernel
Date: Tue, 21 Dec 2004 21:05:36 -0800 [thread overview]
Message-ID: <1103691937.23157.14.camel@DreamGate> (raw)
I've been looking at some "iostat" data from a 2.4.26 machine. The
device utilizations are 100 percent, even when the disk is idle, which
is mathematically impossible. By doing some digging, I discovered this
is a kernel bug, caused by "hd->ios_in_flight" going negative. The
relevant code appears to my untrained eyes to be in
drivers/block/ll_rw_blk.c, specifically
static inline void down_ios(struct hd_struct *hd)
{
disk_round_stats(hd);
--hd->ios_in_flight;
}
static inline void up_ios(struct hd_struct *hd)
{
disk_round_stats(hd);
++hd->ios_in_flight;
}
Question: wouldn't a simple refusal to decrement ios_in_flight in
"down_ios" if it's zero fix this, or am I missing something?
Ed Borasky
znmeb@cesmail.net
next reply other threads:[~2004-12-22 5:17 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-22 5:05 M. Edward Borasky [this message]
2004-12-22 11:16 ` Negative "ios_in_flight" in the 2.4 kernel Jens Axboe
2004-12-22 15:19 ` M. Edward Borasky
2004-12-22 15:58 ` Marcelo Tosatti
2004-12-23 8:08 ` Jens Axboe
2004-12-23 15:30 ` M. Edward Borasky
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