Messages in this thread | | | Date | Sun, 27 Jul 2014 11:09:53 -0700 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] tty/n_gsm.c: do not clear gsm_mux entry when the gsm is not closed |
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On Thu, Jul 24, 2014 at 05:17:01PM +0800, xinhui.pan wrote: > If the gsmtty is still used by some process, we could not just > simply clear gsm_mux[gsm->num]. Clear it when gsm is being free. > Otherwise we will hit crashes when userspace close the gsmtty. > > Also add gsm_mux_get() and gsm_mux_put() to make gsm_mux[] is used safely. > We can do activation/deactivation with same gsm more than once now. > This is for fixing the FIXME. > > Signed-off-by: xinhui.pan <xinhuiX.pan@intel.com> > Reviewed-by: Zhang Yanmin <yanmin_zhang@linux.intel.com> > --- > drivers/tty/n_gsm.c | 84 ++++++++++++++++++++++++++++++++++++--------------- > 1 file changed, 60 insertions(+), 24 deletions(-) > > diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c > index 81e7ccb..290df56 100644 > --- a/drivers/tty/n_gsm.c > +++ b/drivers/tty/n_gsm.c > @@ -2020,6 +2020,58 @@ static void gsm_error(struct gsm_mux *gsm, > } > > /** > + * gsm_mux_get - get/fill one entry in gsm_mux > + * @gsm: our gsm > + * > + * Although its name end with get, it don't inc ref-count actually.
Then don't call it a 'get' function :(
> + * get one entry is just like fill pte, first memory access will > + * cause page_fault, the next accesses don't. So do here.
This doesn't make much sense to me, can you please explain it better?
> + */ > +
blank line?
> +static int gsm_mux_get(struct gsm_mux *gsm) > +{ > + int i; > + > + if (gsm->num >= MAX_MUX) /* gsm is alloc by kzalloc, just be careful */ > + return -EIO;
-EIO?
> + if (gsm_mux[gsm->num] == gsm) /* We have already set gsm->num */ > + return 0; > + > + spin_lock(&gsm_mux_lock); > + for (i = 0; i < MAX_MUX; i++) { > + if (gsm_mux[i] == NULL) { > + gsm->num = i; > + gsm_mux[i] = gsm; > + break; > + } > + } > + spin_unlock(&gsm_mux_lock); > + > + if (i == MAX_MUX) > + return -EBUSY; > + return 0; > +} > + > +/** > + * gsm_mux_put - put/clear one entry in gsm_mux > + * @gsm: our gsm > + * > + * Although its name end with put, it don't dec ref-count actually. > + * put one entry is just like clear pte, So do here. > + */ > + > +static void gsm_mux_put(struct gsm_mux *gsm) > +{ > + if (gsm->num >= MAX_MUX) > + return; > + > + spin_lock(&gsm_mux_lock); > + if (gsm_mux[gsm->num] == gsm)
How can this not be true?
> + gsm_mux[gsm->num] = NULL; > + spin_unlock(&gsm_mux_lock); > +}
Why can't you do dynamic reference counting of your structure, that would allow you to get rid of your global array, right?
thanks,
greg k-h
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