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    SubjectRe: [BUG] AIC7*** SMP deadlock in ahc_linux_free_device
    Herbert Xu <> wrote:
    > The del_timer_sync call in ahc_linux_free_device added in 2.5.67
    > leads to an SMP deadlock when the function is called from the timer
    > itself in ahc_linux_dev_timed_unfreeze.

    Yup, that will deadlock every time on SMP. The below should fix it.

    > I haven't dug too deeply but it seems that there are also possible
    > races where ahc_linux_free_device can be called twice on the same
    > dev. Once from the timer and then again from a non-timer location.

    Possibly, although it might be the case that external locking and
    refcounting prevent this from happening (hopes).

    diff -puN drivers/scsi/aic7xxx/aic7xxx_osm.c~aic7xxx-deadlock-fix drivers/scsi/aic7xxx/aic7xxx_osm.c
    --- 25/drivers/scsi/aic7xxx/aic7xxx_osm.c~aic7xxx-deadlock-fix Tue Feb 17 17:21:44 2004
    +++ 25-akpm/drivers/scsi/aic7xxx/aic7xxx_osm.c Tue Feb 17 17:21:44 2004
    @@ -3969,11 +3969,10 @@ ahc_linux_alloc_device(struct ahc_softc

    static void
    -ahc_linux_free_device(struct ahc_softc *ahc, struct ahc_linux_device *dev)
    +__ahc_linux_free_device(struct ahc_softc *ahc, struct ahc_linux_device *dev)
    struct ahc_linux_target *targ;

    - del_timer_sync(&dev->timer);
    targ = dev->target;
    targ->devices[dev->lun] = NULL;
    free(dev, M_DEVBUF);
    @@ -3983,6 +3982,13 @@ ahc_linux_free_device(struct ahc_softc *
    ahc_linux_free_target(ahc, targ);

    +static void
    +ahc_linux_free_device(struct ahc_softc *ahc, struct ahc_linux_device *dev)
    + del_timer_sync(&dev->timer);
    + __ahc_linux_free_device(ahc, dev);
    ahc_send_async(struct ahc_softc *ahc, char channel,
    u_int target, u_int lun, ac_code code, void *arg)
    @@ -4693,7 +4699,7 @@ ahc_linux_dev_timed_unfreeze(u_long arg)
    ahc_linux_run_device_queue(ahc, dev);
    if (TAILQ_EMPTY(&dev->busyq)
    && dev->active == 0)
    - ahc_linux_free_device(ahc, dev);
    + __ahc_linux_free_device(ahc, dev);
    ahc_unlock(ahc, &s);


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