Messages in this thread | | | Date | Wed, 22 Dec 2004 12:16:43 +0100 | From | Jens Axboe <> | Subject | Re: Negative "ios_in_flight" in the 2.4 kernel |
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On Tue, Dec 21 2004, M. Edward Borasky wrote: > 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?
That would paper over the real bug, but it will work for you.
-- Jens Axboe
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