Messages in this thread Patch in this message | | | Subject | Re: [patch] avoid unaligned access when accessing poll stack | From | Jes Sorensen <> | Date | 31 Mar 2006 11:18:57 -0500 |
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>>>>> "Andi" == Andi Kleen <ak@suse.de> 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@sgi.com>
--- 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 ... */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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