From 1bc2774d866444c5b316fd1dc2b782f20c762cf4 Mon Sep 17 00:00:00 2001 From: Eliezer Tamir Date: Tue, 2 Jul 2013 23:22:47 +0300 Subject: net: convert lls to use time_in_range() Time in range will fail safely if we move to a different cpu with an extremely large clock skew. Add time_in_range64() and convert lls to use it. changelog: v2 - fixed double call to sched_clock in can_poll_ll - fixed checkpatchisms Signed-off-by: Eliezer Tamir Signed-off-by: David S. Miller --- include/linux/jiffies.h | 4 ++++ include/net/ll_poll.h | 26 +++++++++++++++++--------- 2 files changed, 21 insertions(+), 9 deletions(-) (limited to 'include') diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index 8fb8edf12417..97ba4e78a37e 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -139,6 +139,10 @@ static inline u64 get_jiffies_64(void) ((__s64)(a) - (__s64)(b) >= 0)) #define time_before_eq64(a,b) time_after_eq64(b,a) +#define time_in_range64(a, b, c) \ + (time_after_eq64(a, b) && \ + time_before_eq64(a, c)) + /* * These four macros compare jiffies and 'a' for convenience. */ diff --git a/include/net/ll_poll.h b/include/net/ll_poll.h index 6c06f7c0a22d..b76f004f18a9 100644 --- a/include/net/ll_poll.h +++ b/include/net/ll_poll.h @@ -67,19 +67,23 @@ static inline u64 ll_sched_clock(void) /* we don't mind a ~2.5% imprecision so <<10 instead of *1000 * sk->sk_ll_usec is a u_int so this can't overflow */ -static inline u64 ll_sk_end_time(struct sock *sk) +static inline u64 ll_sk_run_time(struct sock *sk) { - return ((u64)ACCESS_ONCE(sk->sk_ll_usec) << 10) + ll_sched_clock(); + return (u64)ACCESS_ONCE(sk->sk_ll_usec) << 10; } /* in poll/select we use the global sysctl_net_ll_poll value * only call sched_clock() if enabled */ -static inline u64 ll_end_time(void) +static inline u64 ll_run_time(void) { - u64 end_time = ACCESS_ONCE(sysctl_net_ll_poll); + return (u64)ACCESS_ONCE(sysctl_net_ll_poll) << 10; +} - return end_time ? (end_time << 10) + ll_sched_clock() : 0; +/* if flag is not set we don't need to know the time */ +static inline u64 ll_start_time(unsigned int flag) +{ + return flag ? ll_sched_clock() : 0; } static inline bool sk_valid_ll(struct sock *sk) @@ -88,9 +92,12 @@ static inline bool sk_valid_ll(struct sock *sk) !need_resched() && !signal_pending(current); } -static inline bool can_poll_ll(u64 end_time) +/* careful! time_in_range64 will evaluate now twice */ +static inline bool can_poll_ll(u64 start_time, u64 run_time) { - return !time_after64(ll_sched_clock(), end_time); + u64 now = ll_sched_clock(); + + return time_in_range64(now, start_time, start_time + run_time); } /* when used in sock_poll() nonblock is known at compile time to be true @@ -98,7 +105,8 @@ static inline bool can_poll_ll(u64 end_time) */ static inline bool sk_poll_ll(struct sock *sk, int nonblock) { - u64 end_time = nonblock ? 0 : ll_sk_end_time(sk); + u64 start_time = ll_start_time(!nonblock); + u64 run_time = ll_sk_run_time(sk); const struct net_device_ops *ops; struct napi_struct *napi; int rc = false; @@ -129,7 +137,7 @@ static inline bool sk_poll_ll(struct sock *sk, int nonblock) LINUX_MIB_LOWLATENCYRXPACKETS, rc); } while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) && - can_poll_ll(end_time)); + can_poll_ll(start_time, run_time)); rc = !skb_queue_empty(&sk->sk_receive_queue); out: -- cgit v1.2.3