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net: convert lls to use time_in_range()

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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 <eliezer.tamir@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eliezer Tamir 2013-07-02 23:22:47 +03:00 committed by David S. Miller
parent 7e6d4da837
commit 1bc2774d86
3 changed files with 27 additions and 13 deletions
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10
fs/select.c
View File

@ -403,7 +403,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
int retval, i, timed_out = 0;
unsigned long slack = 0;
unsigned int ll_flag = ll_get_flag();
u64 ll_time = ll_end_time();
u64 ll_start = ll_start_time(ll_flag);
u64 ll_time = ll_run_time();
rcu_read_lock();
retval = max_select_fd(n, fds);
@ -498,7 +499,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
}
/* only if on, have sockets with POLL_LL and not out of time */
if (ll_flag && can_ll && can_poll_ll(ll_time))
if (ll_flag && can_ll && can_poll_ll(ll_start, ll_time))
continue;
/*
@ -770,7 +771,8 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
int timed_out = 0, count = 0;
unsigned long slack = 0;
unsigned int ll_flag = ll_get_flag();
u64 ll_time = ll_end_time();
u64 ll_start = ll_start_time(ll_flag);
u64 ll_time = ll_run_time();
/* Optimise the no-wait case */
if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
@ -819,7 +821,7 @@ static int do_poll(unsigned int nfds, struct poll_list *list,
break;
/* only if on, have sockets with POLL_LL and not out of time */
if (ll_flag && can_ll && can_poll_ll(ll_time))
if (ll_flag && can_ll && can_poll_ll(ll_start, ll_time))
continue;
/*

4
include/linux/jiffies.h
View File

@ -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.
*/

26
include/net/ll_poll.h
View File

@ -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: