From: David Laight <redacted>
Date: Tue, 1 Jul 2014 13:14:32 +0000

From: David Laight

quoted

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 <redacted>
---
 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

...

quoted

@@ -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' ?

Yes, it does.