From: Tejun Heo <tj@kernel.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org
Subject: Re: [PATCH 02/24] workqueue: defer work to a draining queue
Date: Mon, 19 Dec 2011 13:49:24 -0800 [thread overview]
Message-ID: <20111219214924.GA6256@google.com> (raw)
In-Reply-To: <20111217023318.15036.77389.stgit@localhost6.localdomain6>
Hello,
On Fri, Dec 16, 2011 at 06:33:18PM -0800, Dan Williams wrote:
> commit 9c5a2ba7 "workqueue: separate out drain_workqueue() from
> destroy_workqueue()" provided drain_workqueue() for users like libsas to
> use for flushing events.
>
> When libsas drains it wants currently queued and chained events to be
> flushed, but it fully expects to continue issuing unchained events with
> the expectation that they are serviced sometime after the drain.
>
> For external users of drain_workqueue() arrange for unchained work to be
> queued after the drain completes, if the caller cares if unchained work
> was queued as a result of the drain it can check for a non-zero return
> value. Deferred work is guaranteed to be at least queued when
> drain_workqueue() returns, and visible to flush_workqueue() users as
> well.
>
> Unfortunately this causes the promotion of workqueue_lock to hard-irq
> safe and does not guarantee that work submitted via queue_work_on() runs
> on the specified cpu if it gets deferred.
>
> Cc: Tejun Heo <tj@kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Dan, as I replied before, I'm not a big fan of this approach. For
now, I think it would be best to add private wrapper in libsas to
support deferring unchained work items while draining.
Thanks.
--
tejun
next prev parent reply other threads:[~2011-12-19 21:49 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-17 2:33 [PATCH 00/24] libsas: eh reworks (ata-eh vs discovery, races, ...) Dan Williams
2011-12-17 2:33 ` [PATCH 01/24] workqueue: promote workqueue_lock to hard-irq safe Dan Williams
2011-12-17 2:33 ` [PATCH 02/24] workqueue: defer work to a draining queue Dan Williams
2011-12-19 21:49 ` Tejun Heo [this message]
2011-12-19 22:01 ` Dan Williams
2011-12-19 22:08 ` Tejun Heo
2011-12-19 22:25 ` Williams, Dan J
2011-12-17 2:33 ` [PATCH 03/24] scsi: use drain_workqueue Dan Williams
2011-12-17 2:33 ` [PATCH 04/24] libsas: remove unused ata_task_resp fields Dan Williams
2011-12-17 12:51 ` Sergei Shtylyov
2011-12-19 1:38 ` Jack Wang
2011-12-17 2:33 ` [PATCH 05/24] libsas: kill sas_slave_destroy Dan Williams
2011-12-17 2:33 ` [PATCH 06/24] libsas: fix domain_device leak Dan Williams
2011-12-19 2:32 ` Jack Wang
2011-12-17 2:33 ` [PATCH 07/24] libsas: fix leak of dev->sata_dev.identify_[packet_]device Dan Williams
2011-12-19 2:38 ` Jack Wang
2011-12-17 2:33 ` [PATCH 08/24] libsas: replace event locks with atomic bitops Dan Williams
2011-12-17 2:33 ` [PATCH 09/24] libsas: remove ata_port.lock management duties from lldds Dan Williams
2011-12-17 2:33 ` [PATCH 10/24] libsas: prevent domain rediscovery competing with ata error handling Dan Williams
2011-12-17 2:34 ` [PATCH 11/24] libsas: use ->set_dmamode to notify lldds of NCQ parameters Dan Williams
2011-12-17 2:34 ` [PATCH 12/24] libsas: kill invocation of scsi_eh_finish_cmd from sas_ata_task_done Dan Williams
2011-12-17 2:34 ` [PATCH 13/24] libsas: close error handling vs sas_ata_task_done() race Dan Williams
2011-12-17 2:34 ` [PATCH 14/24] libsas: prevent double completion of scmds from eh Dan Williams
2011-12-17 13:08 ` Sergei Shtylyov
2011-12-18 19:19 ` Dan Williams
2011-12-17 13:13 ` Sergei Shtylyov
2011-12-18 19:24 ` Dan Williams
2011-12-17 2:34 ` [PATCH 15/24] libsas: fix timeout vs completion race Dan Williams
2011-12-17 2:34 ` [PATCH 16/24] libsas: let libata handle command timeouts Dan Williams
2011-12-17 2:34 ` [PATCH 17/24] libsas: defer SAS_TASK_NEED_DEV_RESET commands to libata Dan Williams
2011-12-17 2:34 ` [PATCH 18/24] libsas: use libata-eh-reset for sata rediscovery fis transmit failures Dan Williams
2011-12-17 2:34 ` [PATCH 19/24] libsas: execute transport link resets with libata-eh via host workqueue Dan Williams
2011-12-17 2:34 ` [PATCH 20/24] libsas: sas_phy_enable via transport_sas_phy_reset Dan Williams
2011-12-17 2:34 ` [PATCH 21/24] libsas: Remove redundant phy state notification calls Dan Williams
2011-12-17 2:35 ` [PATCH 22/24] libsas: add mutex for SMP task execution Dan Williams
2011-12-17 2:35 ` [PATCH 23/24] libsas: async ata-eh Dan Williams
2011-12-17 2:35 ` [PATCH 24/24] libsas: poll for ata device readiness after reset Dan Williams
2011-12-20 6:18 ` Jack Wang
2011-12-20 7:08 ` Williams, Dan J
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