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authorEliezer Tamir <eliezer.tamir@linux.intel.com>2013-07-02 23:22:47 +0300
committerDavid S. Miller <davem@davemloft.net>2013-07-02 15:53:53 -0700
commit1bc2774d866444c5b316fd1dc2b782f20c762cf4 (patch)
treedfadce12c9f45c80cd372b27456151be000c8aee
parent7e6d4da837385d9aa2e5fd84e0a6042cddc9e708 (diff)
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 <eliezer.tamir@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--fs/select.c10
-rw-r--r--include/linux/jiffies.h4
-rw-r--r--include/net/ll_poll.h26
3 files changed, 27 insertions, 13 deletions
diff --git a/fs/select.c b/fs/select.c
index 36540754bad7..f28a58592725 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -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;
/*
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: