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Commit 1bc2774d authored by Eliezer Tamir's avatar Eliezer Tamir Committed by David S. Miller
Browse files

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: default avatarEliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7e6d4da8

fs/select.c

+6 −4
Original line number Diff line number Diff line
@@ -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;



		/*

include/linux/jiffies.h

+4 −0
Original line number Diff line number Diff line
@@ -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.

 */

include/net/ll_poll.h

+17 −9
Original line number Diff line number Diff line
@@ -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: