[PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[Julia Lawall]

From: Julia Lawall <julia@diku.dk>

As noted by Akinobu Mita in patch b1fceac2b9e04d278316b2faddf276015fc06e3b,
alloc_bootmem and related functions never return NULL and always return a
zeroed region of memory.  Thus a NULL test or memset after calls to these
functions is unnecessary.

 arch/ia64/kernel/iosapic.c |    2 --
 1 file changed, 2 deletions(-)

This was fixed using the following semantic patch.
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
expression E;
statement S;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\)(...)
... when != E
(
- BUG_ON (E == NULL);
|
- if (E == NULL) S
)

@@
expression E,E1;
@@

E = \(alloc_bootmem\|alloc_bootmem_low\|alloc_bootmem_pages\|alloc_bootmem_low_pages\)(...)
... when != E
- memset(E,0,E1);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
---

diff -u -p a/arch/ia64/kernel/iosapic.c b/arch/ia64/kernel/iosapic.c
--- a/arch/ia64/kernel/iosapic.c
+++ b/arch/ia64/kernel/iosapic.c
@@ -558,8 +558,6 @@ static struct iosapic_rte_info * __init_
 	if (!iosapic_kmalloc_ok && list_empty(&free_rte_list)) {
 		rte = alloc_bootmem(sizeof(struct iosapic_rte_info) *
 				    NR_PREALLOCATE_RTE_ENTRIES);
-		if (!rte)
-			return NULL;
 		for (i = 0; i < NR_PREALLOCATE_RTE_ENTRIES; i++, rte++)
 			list_add(&rte->rte_list, &free_rte_list);
 	}

RE: [PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[Luck, Tony]

> As noted by Akinobu Mita in patch b1fceac2b9e04d278316b2faddf276015fc06e3b,
> alloc_bootmem and related functions never return NULL and always return a
> zeroed region of memory.  Thus a NULL test or memset after calls to these
> functions is unnecessary.

There is no commit b1fceac2b9e04d278316b2faddf276015fc06e3b in Linus' tree.

In addition the current alloc_bootmem() is a macro that uses __alloc_bootmem
which most defintely can return NULL.

Is this against -mm or linux-next?

-Tony

RE: [PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[Julia Lawall]

On Tue, 24 Jun 2008, Luck, Tony wrote:

> > As noted by Akinobu Mita in patch b1fceac2b9e04d278316b2faddf276015fc06e3b,
> > alloc_bootmem and related functions never return NULL and always return a
> > zeroed region of memory.  Thus a NULL test or memset after calls to these
> > functions is unnecessary.
> 
> There is no commit b1fceac2b9e04d278316b2faddf276015fc06e3b in Linus' tree.

I am not sure to know how to tell precisely where you are looking, but you 
can find it here:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=b1fceac2b9e04d278316b2faddf276015fc06e3b


> In addition the current alloc_bootmem() is a macro that uses __alloc_bootmem
> which most defintely can return NULL.

The "return NULL;" at the bottom of __alloc_bootmem is preceded by 
panic("Out of memory");, which I assume cannot return?

> Is this against -mm or linux-next?

I pull files from the following git repository:

git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git

julia

RE: [PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[Luck, Tony]

> In addition the current alloc_bootmem() is a macro that uses __alloc_bootmem
> which most defintely can return NULL.

        ...
        panic("Out of memory");
        return NULL;
}

Oops ... that "panic" call before the "return NULL" makes the
above statement totally wrong.

-Tony

RE: [PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[Luck, Tony]

>> There is no commit b1fceac2b9e04d278316b2faddf276015fc06e3b in Linus' tree.
>
> I am not sure to know how to tell precisely where you are looking, but you
> can find it here:

You are right ... I'm not at all sure where I was looking either.  I cut
& pasted the commit to a "git show ....", and it came up with nothing.  But
now it works!  Some strange user error on my part.  Sorry.

-Tony

RE: [PATCH 3/14] arch/ia64: Eliminate NULL test and memset after alloc_bootmem

[Julia Lawall]

On Tue, 24 Jun 2008, Luck, Tony wrote:

> > In addition the current alloc_bootmem() is a macro that uses __alloc_bootmem
> > which most defintely can return NULL.
> 
>         ...
>         panic("Out of memory");
>         return NULL;
> }
> 
> Oops ... that "panic" call before the "return NULL" makes the
> above statement totally wrong.

Thanks.  I was worried there might be somewhere a non-aborting version of 
panic.  But that would be really confusing...

julia