I think this is caused by my patch to scsi_next_command()
(on or about 11/11) causing it to call put_device() and
invoke the kobject's release() function while in soft
interrupt. My patch should be removed ... although I
don't have an alternate solution in mind for the original
problem which was an "oops with USB Storage on 2.6.14".
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Andrew Morton
> Sent: Friday, December 02, 2005 2:32 PM
> To: Wu Fengguang
> Cc: [email protected]; [email protected]
> Subject: Re: [SCSI BUG 2.6.15-rc3-mm1] scheduling while
> atomic on boot time
>
> Wu Fengguang <[email protected]> wrote:
> >
> > My server occasionally crashes on boot time, this has been
> happening in many
> > recent kernel versions(at least from 2.6.14-rcx). It is
> rare enough, I setup
> > netconsole and rebooted numerous times, but still failed to
> catch it. Luckily
> > it happened again this time, and does not panic. Here is the logs.
> >
> > Thanks,
> > Wu
> >
> > Error messages:
> > [4294676.927000] scheduling while atomic: ksoftirqd/0/0x00000200/3
> > [4294676.927000] [dump_stack+21/32] dump_stack+0x15/0x20
> > [4294676.927000] [schedule+3563/3584] schedule+0xdeb/0xe00
> > [4294676.927000] [__down+138/272] __down+0x8a/0x110
> > [4294676.927000] [__sched_text_start+10/16] <6>scsi[0]:
> scanning scsi channel 1 [Phy 1] for non-raid devices
> > [4294676.927000] __down_failed+0xa/0x10
> > [4294676.927000] [.text.lock.main+43/71] .text.lock.main+0x2b/0x47
> > [4294676.928000] [device_del+62/112] device_del+0x3e/0x70
> > [4294676.928000] [scsi_target_reap+137/176]
> scsi_target_reap+0x89/0xb0
> > [4294676.928000] [scsi_device_dev_release+251/400]
> scsi_device_dev_release+0xfb/0x190
> > [4294676.928000] [device_release+23/80] device_release+0x17/0x50
> > [4294676.928000] [kobject_cleanup+116/128]
> kobject_cleanup+0x74/0x80
> > [4294676.928000] [kobject_release+11/16] kobject_release+0xb/0x10
> > [4294676.929000] [kref_put+52/160] kref_put+0x34/0xa0
> > [4294676.929000] [kobject_put+20/32] kobject_put+0x14/0x20
> > [4294676.929000] [put_device+17/32] put_device+0x11/0x20
> > [4294676.929000] [scsi_next_command+48/64]
> scsi_next_command+0x30/0x40
> > [4294676.929000] [scsi_end_request+165/192]
> scsi_end_request+0xa5/0xc0
> > [4294676.929000] [scsi_io_completion+540/1152]
> scsi_io_completion+0x21c/0x480
> > [4294676.929000] [scsi_generic_done+43/64]
> scsi_generic_done+0x2b/0x40
> > [4294676.930000] [scsi_finish_command+146/240]
> scsi_finish_command+0x92/0xf0
> > [4294676.930000] [scsi_softirq+215/320] scsi_softirq+0xd7/0x140
> > [4294676.930000] [__do_softirq+216/240] __do_softirq+0xd8/0xf0
> > [4294676.930000] [do_softirq+74/96] do_softirq+0x4a/0x60
> > [4294676.930000] =======================
>
> Which device driver are you using?
>
> This is just a warning - it won't necessarily cause a crash
> and in this
> case it didn't appear to do so.
>
> I seem to recall diagnosing this exact locking problem a
> month or so ago,
> and cc'ing linux-scsi on that analysis.
> -
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>
On Fri, 2005-12-02 at 15:35 -0500, goggin, edward wrote:
> I think this is caused by my patch to scsi_next_command()
> (on or about 11/11) causing it to call put_device() and
> invoke the kobject's release() function while in soft
> interrupt. My patch should be removed ... although I
> don't have an alternate solution in mind for the original
> problem which was an "oops with USB Storage on 2.6.14".
Yes and no.
Reverting your patch won't fix the problem because scsi_put_command()
will then relinquish the last reference to the device and trigger the
same warning. Additionally, blk_run_queue now stands a good chance of
running on a freed queue which could trigger a panic.
The problem seems to be that device_del() is apparently requiring user
context, if that's true, this will bite us not only here, but all over
the place ... in fact the fix might have to be to do the target reap
through a workqueue.
Regardless, your patch isn't the culprit here, it's just the thing which
is doing the last put.
James