copy_to/from_user and a bottom half

From: Alex Ivchenko (aivchenko@ueidaq.com)
Date: Thu May 18 2000 - 11:53:07 EDT

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    Hi,

    I tried to speed up a driver and moved copy_to_user()
    from ioctl to the bottom half of interrupt handler.

    access_ok() returns TRUE (of course, user address is valid), but
    copy_to_user() couldn't copy anything into the user space.

    bh is sched like:
            queue_task(&pd_bh_task, &tq_immediate);
            mark_bh(IMMEDIATE_BH);

    and spin_lock_irqsave() is NOT used in bh as well as any other
    sync stuff.

    I assumed that if lock is not set kernel could use exception handlers
    (according to Documentation/exception.txt) to get user space mem page.

    Could you tell me what is wrong?

    Thanks,
    Alex 

    --
Alex Ivchenko, Ph.D.
United Electronic Industries, Inc.
"The High-Performance Alternative (tm)"
--
10 Dexter Avenue
Watertown, Massachusetts 02472
Tel: (617) 924-1155 x 222 Fax: (617) 924-1441
http://www.ueidaq.com

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