Re: [Bug 12945] New: SCSI Generic (sg): BUG: sleeping function called from invalid context

[Andrew Morton <akpm@linux-foundation.org>]

(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Thu, 26 Mar 2009 12:27:53 GMT bugzilla-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=12945
> 
>            Summary: SCSI Generic (sg): BUG: sleeping function called from
>                     invalid context
>            Product: SCSI Drivers
>            Version: 2.5
>     Kernel Version: 2.6.28.9
>           Platform: All
>         OS/Version: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>         AssignedTo: scsi_drivers-other@kernel-bugs.osdl.org
>         ReportedBy: txtoxtox285@googlemail.com
>         Regression: No
> 
> 
> Created an attachment (id=20685)
>  --> (http://bugzilla.kernel.org/attachment.cgi?id=20685)
> Stack trace on program kill (2.6.28.9)
> 
> I am experimenting with CD audio extraction. I use the SCSI Generic driver for
> this.
> 
> My test program uses read() and write() (instead of ioctl) to send requests to
> the driver and receive responses. I use SG_FLAG_DIRECT_IO.
> 
> When I kill my program (because I don't want to wait until it has ripped the
> entire CD), I am often rewarded with messages like "BUG: sleeping function
> called from invalid context at linux-2.6.28.9/include/linux/pagemap.h:347". I
> have attached typical stack trace.
> 
> Another case when I hit this BUG is when I set a time out and the CD drive
> doesn't respond fast enough. A stack trace is attached.

> [34215.786870] BUG: sleeping function called from invalid context at /mnt/var-pub/src/linux-2.6.28.9/include/linux/pagemap.h:347
> [34215.786880] in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper
> [34215.786886] Pid: 0, comm: swapper Not tainted 2.6.28.9 #1
> [34215.786890] Call Trace:
> [34215.786894]  <IRQ>  [<ffffffff8026c4cc>] set_page_dirty_lock+0x1a/0x45
> [34215.786911]  [<ffffffff802ae17d>] bio_unmap_user+0x1e/0x4a
> [34215.786920]  [<ffffffff802e876b>] __blk_rq_unmap_user+0x14/0x20
> [34215.786928]  [<ffffffff80210852>] pit_next_event+0x2e/0x49
> [34215.786934]  [<ffffffff802e8795>] blk_rq_unmap_user+0x1e/0x4b
> [34215.786965]  [<ffffffffa0163475>] sg_finish_rem_req+0x6d/0x88 [sg]
> [34215.786979]  [<ffffffffa0164ef3>] sg_rq_end_io+0x131/0x205 [sg]
> [34215.786986]  [<ffffffff802e5c1f>] end_that_request_last+0x58/0x194
> [34215.786992]  [<ffffffff802e5e00>] blk_end_io+0x48/0x7d
> [34215.787019]  [<ffffffffa0026bef>] scsi_next_command+0x219/0x283 [scsi_mod]
> [34215.787039]  [<ffffffffa00279b1>] scsi_io_completion+0x181/0x53b [scsi_mod]
> [34215.787047]  [<ffffffff802e9737>] blk_done_softirq+0x5f/0x6d
> [34215.787054]  [<ffffffff80230787>] __do_softirq+0x5e/0xf8
> [34215.787061]  [<ffffffff8020ca8c>] call_softirq+0x1c/0x28
> [34215.787067]  [<ffffffff8020d6bc>] do_softirq+0x2c/0x68
> [34215.787073]  [<ffffffff80230696>] irq_exit+0x36/0x82
> [34215.787079]  [<ffffffff8020d79e>] do_IRQ+0xa6/0xb8
> [34215.787085]  [<ffffffff8020c256>] ret_from_intr+0x0/0xa
> [34215.787088]  <EOI>  [<ffffffff8034f648>] menu_reflect+0x0/0x6d
> [34215.787112]  [<ffffffffa0147d51>] acpi_idle_enter_simple+0x170/0x1d6 [processor]
> [34215.787127]  [<ffffffffa0147d47>] acpi_idle_enter_simple+0x166/0x1d6 [processor]
> [34215.787134]  [<ffffffff8034eb32>] cpuidle_idle_call+0x73/0xb1
> [34215.787140]  [<ffffffff8020ac2a>] cpu_idle+0x3c/0x73

Argh.  sg_finish_rem_req() is called from interrupt context.  But
blk_rq_unmap_user() can run
__bio_unmap_user()->set_page_dirty_lock()->lock_page(), which can call
schedule().  If it does call schedule(), the machine will crash.

afacit, blk_rq_unmap_user() has always been a can-sleep function, and
this is a regression caused by

commit 6e5a30cba5e7c03b2cd564e968f1dd667a0f7c42
Author:     FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
AuthorDate: Thu Aug 28 16:17:08 2008 +0900
Commit:     Jens Axboe <jens.axboe@oracle.com>
CommitDate: Thu Oct 9 08:56:10 2008 +0200

    sg: convert the direct IO path to use the block layer
    
    This patch converts the direct IO path (SG_FLAG_DIRECT_IO) to use the
    block layer functions (blk_get_request, blk_execute_rq_nowait,
    blk_rq_map_user, etc) instead of scsi_execute_async().
    
    Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
    Signed-off-by: Douglas Gilbert <dougg@torque.net>
    Cc: Mike Christie <michaelc@cs.wisc.edu>
    Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
    Signed-off-by: Jens Axboe <jens.axboe@oracle.com>