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.ta...@linux.intel.com>
---
fs/select.c | 10 ++++++----
include/linux/jiffies.h | 4 ++++
include/net/ll_poll.h | 26 +++++++++++++++++---------
3 files changed, 27 insertions(+), 13 deletions(-)
diff --git a/fs/select.c b/fs/select.c
index 3654075..f28a585 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 8fb8edf..97ba4e7 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 6c06f7c..b76f004 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:
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
