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>>>>> "Andi" == Andi Kleen <ak@xxxxxxx> writes:
Andi> On Friday 31 March 2006 17:38, Jes Sorensen wrote:
>> Hi,
>>
>> Patch 70674f95c0a2ea694d5c39f4e514f538a09be36f [PATCH] Optimize
>> select/poll by putting small data sets on the stack resulted in the
>> poll stack being 4-byte aligned on 64-bit architectures, causing
>> misaligned accesses to elements in the array.
>>
>> This patch fixes it by declaring the stack in terms of 'long'
>> instead of 'char'.
Andi> You should do that for poll too then.
I assume you mean select().
Updated patch attached.
Jes
Force alignment of poll and select stacks to long to avoid unaligned
access on 64 bit architectures.
Signed-off-by: Jes Sorensen <jes@xxxxxxx>
---
fs/select.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
Index: linux-2.6/fs/select.c
===================================================================
--- linux-2.6.orig/fs/select.c
+++ linux-2.6/fs/select.c
@@ -314,7 +314,7 @@
int ret, size, max_fdset;
struct fdtable *fdt;
/* Allocate small arguments on the stack to save memory and be faster */
- char stack_fds[SELECT_STACK_ALLOC];
+ long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
ret = -EINVAL;
if (n < 0)
@@ -639,8 +639,10 @@
struct poll_list *walk;
struct fdtable *fdt;
int max_fdset;
- /* Allocate small arguments on the stack to save memory and be faster */
- char stack_pps[POLL_STACK_ALLOC];
+ /* Allocate small arguments on the stack to save memory and be
+ faster - use long to make sure the buffer is aligned properly
+ on 64 bit archs to avoid unaligned access */
+ long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
struct poll_list *stack_pp = NULL;
/* Do a sanity check on nfds ... */
-
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