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SubjectRe: [PATCH 0/8] sdhci: Move real work out of an atomic context
Hi,

On Wed, Sep 08, 2010 at 10:37:41PM +0100, Chris Ball wrote:
> Hi Andrew,
>
> On Tue, Sep 07, 2010 at 03:38:13PM -0700, Andrew Morton wrote:
> > > I noticed no throughput drop neither with PIO transfers nor
> > > with DMA (tested on MPC8569E CPU), while latencies should be
> > > greatly improved.
> >
> > This patchset isn't causing any problems yet, but may do so in the
> > future and will impact the validity of any testing. It seems to be
> > kind of stuck. Should I drop it all?
>
> I suggest keeping it -- I'll find time to test it out here soon, and
> will keep it in mind as a possible regression cause.

Am running this now. The first thing I'm noticing is a repeated BUG():

[ 7.288186] Write protecting the kernel read-only data: 1072k
[ 7.306446] BUG: sleeping function called from invalid context at kernel/mutex.c:94
[ 7.324375] in_atomic(): 1, irqs_disabled(): 0, pid: 532, name: mmc2/0
[ 7.340989] Pid: 532, comm: mmc2/0 Not tainted 2.6.35.4_xo1.5-20100908.2141.olpc.44f3b38_DIRTY #1
[ 7.360129] Call Trace:
[ 7.372843] [<b04193ce>] __might_sleep+0xd9/0xe0
[ 7.387864] [<b07260cc>] mutex_lock+0x1c/0x2a
[ 7.402576] [<b06396e8>] sdhci_led_control+0x1a/0x41
[ 7.417727] [<b063bece>] led_trigger_event+0x42/0x5c
[ 7.432807] [<b06326f8>] mmc_request_done+0x56/0x6f
[ 7.447597] [<b063a2d1>] sdhci_finish_work+0xc8/0xcd
[ 7.462643] [<b063a209>] ? sdhci_finish_work+0x0/0xcd
[ 7.477941] [<b0432776>] worker_thread+0x165/0x1ed
[ 7.492856] [<b063a209>] ? sdhci_finish_work+0x0/0xcd
[ 7.508204] [<b0435591>] ? autoremove_wake_function+0x0/0x34
[ 7.524178] [<b0432611>] ? worker_thread+0x0/0x1ed
[ 7.538953] [<b04352a0>] kthread+0x63/0x68
[ 7.552659] [<b043523d>] ? kthread+0x0/0x68
[ 7.566349] [<b0402cf6>] kernel_thread_helper+0x6/0x10
[ 7.709931] udev: starting version 141
[ 7.940374] mmc2: new high speed SDHC card at address e4da
[ 8.058165] mmcblk0: mmc2:e4da SU04G 3.69 GiB
[ 8.135730] mmcblk0: p1 p2

Full dmesg is at http://chris.printf.net/anton-mutex-dmesg.txt.
Anton, the kernel is 2.6.35.4-olpc plus your patchset from -mm.
I can think about how to test on an upstream kernel instead, but
perhaps your own tests simply didn't hit sdhci_led_control().

Andrew, if you want to drop this while the BUG() and potential
performance regressions are worked out, I'd be happy to keep
testing patches from Anton until it's without regressions here.

Thanks,

--
Chris Ball <cjb@laptop.org> <http://printf.net/>
One Laptop Per Child


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