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    Subjectmight_sleep() in copy_{from,to}_user and friends?
    Date
    I have been looking for more places in 2.5 that can be marked 
    might_sleep() and noticed that all the functions in asm/uaccess.h
    are not marked although they sleep if the memory they access
    has to be paged in.

    After adding might_sleep() in ten places in asm-i386/uaccess.h
    and arch/i386/lib/usercopy.c, I have been running this kernel
    for about two weeks. So far, I have found only one place where
    the kernel actually hits this and that one is trivially
    fixable (maintainer cc'd, fix see below).

    The question is if we can expect to find more bugs like
    that if we have might_sleep() in uaccess.h or if the
    extra cycles and the work of changing ~100 places (for all
    architectures) are just not worth it.

    Arnd <><

    ===== sound/core/pcm_native.c 1.17 vs edited =====
    --- 1.17/sound/core/pcm_native.c Sun Oct 13 21:19:17 2002
    +++ edited/sound/core/pcm_native.c Fri Nov 1 12:43:38 2002
    @@ -2014,8 +2014,6 @@
    n = snd_pcm_playback_hw_avail(runtime);
    else
    n = snd_pcm_capture_avail(runtime);
    - if (put_user(n, res))
    - err = -EFAULT;
    break;
    case SNDRV_PCM_STATE_XRUN:
    err = -EPIPE;
    @@ -2026,6 +2024,9 @@
    break;
    }
    spin_unlock_irq(&runtime->lock);
    + if (!ret)
    + if (put_user(n, res))
    + err = -EFAULT;
    return err;
    }

    -
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