From: James Bottomley <James.Bottomley@suse.de>
To: Bart Van Assche <bvanassche@acm.org>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
linux-scsi@vger.kernel.org, hch@lst.de, michaelc@cs.wisc.edu,
hare@suse.de, bharrosh@panasas.com
Subject: Re: [PATCH-v2 00/14] iscsi-target: iSCSI target v4.1.0-rc1 series initial merge
Date: Fri, 25 Mar 2011 10:06:51 -0500 [thread overview]
Message-ID: <1301065611.4073.7.camel@mulgrave.site> (raw)
In-Reply-To: <AANLkTik2UxAO3uZ8r1U0bqYVX+0zHGUAd8uuiPzVQq57@mail.gmail.com>
On Fri, 2011-03-25 at 12:31 +0100, Bart Van Assche wrote:
> On Fri, Mar 25, 2011 at 1:18 AM, James Bottomley
> <James.Bottomley@suse.de> wrote:
> >> OK, so what about an upcall to userspace to create the necessary
> > directories? That could be driven by the kernel and still not require
> > any implementation in configfs.
>
> Hi James,
>
> I might have missed something, but which upcall mechanism are you
> referring to ? Personally I'm not fond of the upcall concept because
> as far as I can see any synchronous upcall mechanism can potentially
> be used to trigger lock inversions not detectable by the PROVE_LOCKING
> mechanism.
Any ... we have relay, netlink, uevent etc.
I don't see how there could be a lock inversion. Upcalls are by
definition asynchronous.
The use case for ibmvscsi, which seems the most pressing, is simply that
on load it unpacks the config information, does the upcall and exits.
The daemon creates the necessary directories with the information and
the vscsi interface is functional once everything is set up. There's no
locking problems in that use case.
> Regarding kernel-space driven directory creation in configfs: I have
> been wondering whether it is possible to implement any configuration
> filesystem such that directories can be created synchronously from
> kernel space without triggering lock inversion. I don't see this as a
> configfs limitation but as an inherent limitation of a configuration
> filesystem. In a similar way a self-declarative kernel interface like
> sysfs has the limitation that it is not possible to add configfs-style
> configuration functionality without triggering lock inversion. Both
> sysfs and configfs have important advantages over mechanisms like
> ioctl() and netlink but there are some disadvantages too.
Explain first what lock inversion problems you see ... those usually
only happen if you have the in the kernel upcall thread waiting for
completion.
James
next prev parent reply other threads:[~2011-03-25 15:07 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-23 3:06 [PATCH-v2 00/14] iscsi-target: iSCSI target v4.1.0-rc1 series initial merge Nicholas A. Bellinger
2011-03-23 3:06 ` Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 01/14] iscsi: Resolve iscsi_proto.h naming conflicts with drivers/target/iscsi Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 02/14] iscsi: Add Serial Number Arithmetic LT and GT into iscsi_proto.h Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 03/14] target: Convert REPORT_LUNs to use int_to_scsilun Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 04/14] iscsi-target: Add iSCSI fabric support for target v4 Nicholas A. Bellinger
2011-04-07 7:34 ` Mike Christie
2011-05-09 16:22 ` Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 05/14] iscsi-target: Add TCM v4 compatiable ConfigFS control plane Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 06/14] iscsi-target: Add configfs fabric dependent statistics Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 07/14] iscsi-target: Add TPG and Device logic Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 08/14] iscsi-target: Add iSCSI Login Negotiation and Parameter logic Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 09/14] iscsi-target: Add CHAP Authentication support using libcrypto Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 10/14] iscsi-target: Add Sequence/PDU list + DataIN response logic Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 11/14] iscsi-target: Add iSCSI Error Recovery Hierarchy support Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 12/14] iscsi-target: Add support for task management operations Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 13/14] iscsi-target: Add misc utility and debug logic Nicholas A. Bellinger
2011-03-23 3:06 ` [PATCH-v2 14/14] iscsi-target: Add Makefile/Kconfig and update TCM top level Nicholas A. Bellinger
2011-03-23 8:54 ` [PATCH-v2 00/14] iscsi-target: iSCSI target v4.1.0-rc1 series initial merge FUJITA Tomonori
2011-03-23 10:22 ` Nicholas A. Bellinger
2011-03-23 11:07 ` FUJITA Tomonori
2011-03-23 21:37 ` Nicholas A. Bellinger
2011-03-23 22:46 ` FUJITA Tomonori
2011-03-23 23:28 ` Nicholas A. Bellinger
2011-03-24 1:29 ` FUJITA Tomonori
2011-03-24 6:59 ` Nicholas A. Bellinger
2011-03-25 0:18 ` James Bottomley
2011-03-25 11:31 ` Bart Van Assche
2011-03-25 15:06 ` James Bottomley [this message]
2011-03-25 18:44 ` Bart Van Assche
2011-03-25 19:34 ` James Bottomley
2011-03-25 19:49 ` Bart Van Assche
2011-03-25 19:54 ` James Bottomley
2011-03-25 20:05 ` Bart Van Assche
2011-03-25 21:14 ` Nicholas A. Bellinger
2011-03-27 10:02 ` FUJITA Tomonori
2011-03-28 8:30 ` Nicholas A. Bellinger
2011-03-28 8:33 ` FUJITA Tomonori
2011-03-27 10:02 ` FUJITA Tomonori
2011-03-28 8:53 ` Nicholas A. Bellinger
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1301065611.4073.7.camel@mulgrave.site \
--to=james.bottomley@suse.de \
--cc=bharrosh@panasas.com \
--cc=bvanassche@acm.org \
--cc=fujita.tomonori@lab.ntt.co.jp \
--cc=hare@suse.de \
--cc=hch@lst.de \
--cc=linux-scsi@vger.kernel.org \
--cc=michaelc@cs.wisc.edu \
--cc=nab@linux-iscsi.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).