Date: Mon, 13 Oct 2014 09:06:04 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "K. Macy" <kmacy@freebsd.org> Cc: Mark Martinec <Mark.Martinec+freebsd@ijs.si>, "freebsd-fs@FreeBSD.org" <freebsd-fs@freebsd.org>, FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: zfs pool import hangs on [tx->tx_sync_done_cv] Message-ID: <6E01BBEDA9984CCDA14F290D26A8E14D@multiplay.co.uk> References: <54372173.1010100@ijs.si><644FA8299BF848E599B82D2C2C298EA7@multiplay.co.uk><54372EBA.1000908@ijs.si><DE7DD7A94E9B4F1FBB3AFF57EDB47C67@multiplay.co.uk><543731F3.8090701@ijs.si><543AE740.7000808@ijs.si><A5BA41116A7F4B23A9C9E469C4146B99@multiplay.co.uk> <CAHM0Q_N%2BC=3qgUnyDkEugOFcL=J8gBjbTg8v45Vz3uT=e=Fn2g@mail.gmail.com>
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----- Original Message -----
From: "K. Macy" <kmacy@freebsd.org>
> A recent quick read of the code would lead me to believe that zio_wait not
> returning there means that the zio never reached the zio_done stage. Parent
> zios seem to yield in a couple of stages in the pipeline if they have
> incomplete children. They determine this by calling zio_wait_for_children
> with zio child types and their corresponding wait type. In so doing they
> set the io_stall to the count of the number of waiters of the first
> non-zero check. This parent I/O will be resumed by the last child zio of
> that type and wait state in zio_notify_parent. I'm sure you know all this -
> but I wrote it to preface asking for the following fields of the zio being
> waited on in dsl_pool_sync_mos: io_stall (i.e, which field in io_children
> is pointed to) *io_stall, io_children[*][*], io_child_list (at a first
> glance just the addresses). The other alternative is that it reexecuting
>has gotten in to a bad place in the state machine so io_reexecute.
Yer I would have got the zio details but typically its "optimised out" by the
compiler, so will need some effort to track that down unfortunately :(
Regards
Steve
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