From: David Laight
> Even if memset() is inlined (as on x86) using it to zero the union
> generates a memory word write of zero, followed by a write of the
> smaller field, and then a read of the word.
> As well as being a lot of instructions the sequence is unlikely to
> be optimised by the store-load forward hardware so will be slow.
>
> Instead allocate a field of the union that is the same size as the
> entire union and write a zero value to it. The compiler will then
> generate the required value in a register.
>
> Signed-off-by: David Laight <david.laight@xxxxxxxxxx>
> ---
> include/net/sctp/command.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
> index 020eb95..5fcd1a7 100644
> --- a/include/net/sctp/command.h
> +++ b/include/net/sctp/command.h
...
> @@ -212,7 +213,6 @@ typedef struct {
> */
> static inline int sctp_init_cmd_seq(sctp_cmd_seq_t *seq)
> {
> - memset(seq, 0, sizeof(sctp_cmd_seq_t));
> return 1; /* We always succeed. */
> }
I've realised that this version of this chunk leaves seq->next_free_slot
and seq->next_cmd uninitialized (they need to be zero).
The next patch in the series contains different initialisers - which are correct.
I guess this needs fixing for 'git bisect' ?
David
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