2022-03-11 21:27:09

by Alexey Dobriyan

Subject: [PATCH 5/5] x86/unwind/orc: delete dead write in __orc_find()

Also move "mid" variable to the innermost scope and delete useless
parenthesis while I'm at it.

Signed-off-by: Alexey Dobriyan (CloudLinux) <[email protected]>
---
arch/x86/kernel/unwind_orc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 2de3c8c5eba9..d38125ea1bf6 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -35,7 +35,7 @@ static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
{
int *first = ip_table;
int *last = ip_table + num_entries - 1;
- int *mid = first, *found = first;
+ int *found = first;

if (!num_entries)
return NULL;
@@ -47,7 +47,7 @@ static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
* ignored when they conflict with a real entry.
*/
while (first <= last) {
- mid = first + ((last - first) / 2);
+ int *mid = first + (last - first) / 2;

if (orc_ip(mid) <= ip) {
found = mid;
--
2.34.1

2022-03-11 21:39:09

by Alexey Dobriyan

Subject: Re: [PATCH 5/5] x86/unwind/orc: delete dead write in __orc_find()

On Fri, Mar 11, 2022 at 03:13:02PM +0000, David Laight wrote:
> From: Alexey Dobriyan
> > Sent: 11 March 2022 14:43
> >
> > Also move "mid" variable to the innermost scope and delete useless
> > parenthesis while I'm at it.
>
> Hiding the definition of 'mid' in the inner scope is pointless.

Not, it is not.

> I'm also not 100% sure that 'found' is always set.

"found" is left as-is by the patch.

> Consider the ip < orc_ip(first) case.

> > --- a/arch/x86/kernel/unwind_orc.c
> > +++ b/arch/x86/kernel/unwind_orc.c
> > @@ -35,7 +35,7 @@ static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
> > {
> > int *first = ip_table;
> > int *last = ip_table + num_entries - 1;
> > - int *mid = first, *found = first;
> > + int *found = first;
> >
> > if (!num_entries)
> > return NULL;
> > @@ -47,7 +47,7 @@ static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
> > * ignored when they conflict with a real entry.
> > */
> > while (first <= last) {
> > - mid = first + ((last - first) / 2);
> > + int *mid = first + (last - first) / 2;
> >
> > if (orc_ip(mid) <= ip) {
> > found = mid;

2022-03-11 22:32:35

by David Laight

Subject: RE: [PATCH 5/5] x86/unwind/orc: delete dead write in __orc_find()

From: Alexey Dobriyan
> Sent: 11 March 2022 14:43
>
> Also move "mid" variable to the innermost scope and delete useless
> parenthesis while I'm at it.

Hiding the definition of 'mid' in the inner scope is pointless.

I'm also not 100% sure that 'found' is always set.
Consider the ip < orc_ip(first) case.

David

>
> Signed-off-by: Alexey Dobriyan (CloudLinux) <[email protected]>
> ---
> arch/x86/kernel/unwind_orc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> index 2de3c8c5eba9..d38125ea1bf6 100644
> --- a/arch/x86/kernel/unwind_orc.c
> +++ b/arch/x86/kernel/unwind_orc.c
> @@ -35,7 +35,7 @@ static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
> {
> int *first = ip_table;
> int *last = ip_table + num_entries - 1;
> - int *mid = first, *found = first;
> + int *found = first;
>
> if (!num_entries)
> return NULL;
> @@ -47,7 +47,7 @@ static struct orc_entry *__orc_find(int *ip_table, struct orc_entry *u_table,
> * ignored when they conflict with a real entry.
> */
> while (first <= last) {
> - mid = first + ((last - first) / 2);
> + int *mid = first + (last - first) / 2;
>
> if (orc_ip(mid) <= ip) {
> found = mid;
> --
> 2.34.1

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