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SubjectRe: [PATCH 01/14] pch_uart: drop double zeroing
On Sun, Sep 20, 2020 at 02:47:11PM +0200, Julia Lawall wrote:
>
>
> On Sun, 20 Sep 2020, Greg Kroah-Hartman wrote:
>
> > On Sun, Sep 20, 2020 at 01:26:13PM +0200, Julia Lawall wrote:
> > > sg_init_table zeroes its first argument, so the allocation of that argument
> > > doesn't have to.
> > >
> > > the semantic patch that makes this change is as follows:
> > > (http://coccinelle.lip6.fr/)
> > >
> > > // <smpl>
> > > @@
> > > expression x,n,flags;
> > > @@
> > >
> > > x =
> > > - kcalloc
> > > + kmalloc_array
> > > (n,sizeof(struct scatterlist),flags)
> > > ...
> > > sg_init_table(x,n)
> > > // </smpl>
> > >
> > > Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
> >
> > It inits the first entry in the array, but what about all of the other
> > ones? Is that "safe" to have uninitialized data in them like your
> > change causes to happen?
>
> Sorry, I don't follow. The complete code is:
>
> priv->sg_tx_p = kcalloc(num, sizeof(struct scatterlist), GFP_ATOMIC);
> if (!priv->sg_tx_p) {
> dev_err(priv->port.dev, "%s:kzalloc Failed\n", __func__);
> return 0;
> }
>
> sg_init_table(priv->sg_tx_p, num); /* Initialize SG table */
>
> and the definition of sg_init_table is:
>
> void sg_init_table(struct scatterlist *sgl, unsigned int nents)
> {
> memset(sgl, 0, sizeof(*sgl) * nents);
> sg_init_marker(sgl, nents);
> }

Ah, missed the "* nents" thing there, sorry, my fault.

greg k-h

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