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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1726978B@AcuExch.aculab.com> Date: Mon, 30 Jun 2014 13:01:08 +0000 From: David Laight <David.Laight@...LAB.COM> To: Network Development <netdev@...r.kernel.org>, "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org> CC: "David S. Miller" <davem@...emloft.net> Subject: [PATCH net-next 3/3] net: sctp: Use pointers (not array indexes) to access sctp_cmd_seq_t.cmds[] Using pointers into sctp_cmd_seq_t.cmds[] lets the compiler generate much better code. Use the last entry first to optimise the overflow check. Signed-off-by: David Laight <david.laight@...lab.com> --- include/net/sctp/command.h | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h index 5fcd1a7..059720c 100644 --- a/include/net/sctp/command.h +++ b/include/net/sctp/command.h @@ -203,8 +203,8 @@ typedef struct { typedef struct { sctp_cmd_t cmds[SCTP_MAX_NUM_COMMANDS]; - __u8 next_free_slot; - __u8 next_cmd; + sctp_cmd_t *last_used_slot; + sctp_cmd_t *next_cmd; } sctp_cmd_seq_t; @@ -213,6 +213,9 @@ typedef struct { */ static inline int sctp_init_cmd_seq(sctp_cmd_seq_t *seq) { + /* cmds[] is filled backwards to simplify the overflow BUG() check */ + seq->last_used_slot = seq->cmds + SCTP_MAX_NUM_COMMANDS; + seq->next_cmd = seq->last_used_slot; return 1; /* We always succeed. */ } @@ -225,10 +228,13 @@ static inline int sctp_init_cmd_seq(sctp_cmd_seq_t *seq) static inline void sctp_add_cmd_sf(sctp_cmd_seq_t *seq, sctp_verb_t verb, sctp_arg_t obj) { - BUG_ON(seq->next_free_slot >= SCTP_MAX_NUM_COMMANDS); + sctp_cmd_t *cmd = seq->last_used_slot - 1; - seq->cmds[seq->next_free_slot].verb = verb; - seq->cmds[seq->next_free_slot++].obj = obj; + BUG_ON(cmd < seq->cmds); + + cmd->verb = verb; + cmd->obj = obj; + seq->last_used_slot = cmd; } /* Return the next command structure in an sctp_cmd_seq. @@ -236,12 +242,10 @@ static inline void sctp_add_cmd_sf(sctp_cmd_seq_t *seq, sctp_verb_t verb, */ static inline sctp_cmd_t *sctp_next_cmd(sctp_cmd_seq_t *seq) { - sctp_cmd_t *retval = NULL; - - if (seq->next_cmd < seq->next_free_slot) - retval = &seq->cmds[seq->next_cmd++]; + if (seq->next_cmd <= seq->last_used_slot) + return NULL; - return retval; + return --seq->next_cmd; } #endif /* __net_sctp_command_h__ */ -- 1.8.1.2 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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