SCSI Generic (sg): BUG: sleeping function called from invalid context

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Quoted 20 lines · On Thu, 26 Mar 2009 12:27:53 GMT [email protected] 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: [email protected]
        ReportedBy: [email protected]
        Regression: No

Created an attachment (id=20685)

Quoted 36 lines

 --> (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

Quoted 8 lines

[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 <[email protected]>
AuthorDate: Thu Aug 28 16:17:08 2008 +0900
Commit:     Jens Axboe <[email protected]>
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 <[email protected]>

Signed-off-by Douglas Gilbert <[email protected]>

Cc Mike Christie <[email protected]>

Cc James Bottomley <[email protected]>

Signed-off-by Jens Axboe <[email protected]>