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    SubjectRe: [alsa-devel] unload Audio drivers while playback stream is active case kernel crash
    At Wed, 14 Jan 2015 12:02:28 +0000,
    Mark Brown wrote:
    >
    > On Wed, Jan 14, 2015 at 11:50:48AM +0100, Takashi Iwai wrote:
    > > Lars-Peter Clausen wrote:
    >
    > > > > OK, so it's not about active stream. From the reporter's description,
    > > > > I supposed that the module gets unloaded while playing a stream, which
    > > > > shouldn't be allowed.
    >
    > > > Well one of the ways to trigger this is to remove the module while the
    > > > stream is active. But it is not exclusively a problem module unload problem.
    > > > E.g. the same happens if you hot-unplug the ASoC card.
    >
    > > Yes, unbinding can trigger a similar problem, ends up the same bad
    > > code path.
    >
    > Right, which was my point - we need to be able to cope with the driver
    > being removed while in use, unbind is just one path where this could
    > happen and the issue isn't specific to unbind.
    >
    > > > I don't think that we need to prevent module unload when a stream is active.
    > > > From a framework point of view is not different from hot-unplug. I don't
    > > > see a reason why we'd jump through hoops to actively forbid removing the
    > > > module once it works just fine.
    >
    > > Well, the module unload means a more drastic cleanup. Even if you
    > > unbind, the code and data are still there while module unload may
    > > clean them up all.
    >
    > > Above all, disallowing the module unload while using is the common
    > > behavior of any other drivers. Why do we have to be a rebel against
    > > all civil manner? :)
    >
    > That's not true for everything

    Hmm, which driver does behave so intentionally? I'm interested in the
    supposed reason behind it.

    > and for ASoC I'd tend to assume that the
    > user knows what they're doing and has a good reason for it; it's
    > certainly something that can be helpful in development.

    The module unload is never considered to be equivalent with hot
    unplug It's more than that.


    Takashi


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