[PATCH 5/9] select: Convert select_estimate_accuracy() to take ktime_t

Dmitry Safonov
2019-09-09T10:24:09Z

Instead of converting the time on the first loop, the same
if (end_time) can be shared. Simplify the loop by taking time
conversion out.

Also prepare the ground for converting poll() restart_block timeout into
ktime_t - that's the only user that leaves it in timespec.
The conversion is needed to introduce an API for ptrace() to get
a timeout from restart_block.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
fs/eventpoll.c | 4 ++--
fs/select.c | 38 ++++++++++++--------------------------
include/linux/poll.h | 2 +-
3 files changed, 15 insertions(+), 29 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index d7f1f5011fac..d5120fc49a39 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1836,9 +1836,9 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
if (timeout > 0) {
struct timespec64 end_time = ep_set_mstimeout(timeout);

- slack = select_estimate_accuracy(&end_time);
+ expires = timespec64_to_ktime(end_time);
to = &expires;
- *to = timespec64_to_ktime(end_time);
+ slack = select_estimate_accuracy(expires);
} else if (timeout == 0) {
/*
* Avoid the unnecessary trip to the wait queue loop, if the
diff --git a/fs/select.c b/fs/select.c
index 2477c202631e..458f2a944318 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -66,7 +66,7 @@ static long __estimate_accuracy(ktime_t slack)
return slack;
}

-u64 select_estimate_accuracy(struct timespec64 *timeout)
+u64 select_estimate_accuracy(ktime_t timeout)
{
ktime_t now, slack;

@@ -77,7 +77,7 @@ u64 select_estimate_accuracy(struct timespec64 *timeout)
return 0;

now = ktime_get();
- slack = now - timespec64_to_ktime(*timeout);
+ slack = now - timeout;

slack = __estimate_accuracy(slack);
if (slack < current->timer_slack_ns)
@@ -490,8 +490,11 @@ static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
timed_out = 1;
}

- if (end_time && !timed_out)
- slack = select_estimate_accuracy(end_time);
+ if (end_time && !timed_out) {
+ expire = timespec64_to_ktime(*end_time);
+ to = &expire;
+ slack = select_estimate_accuracy(expire);
+ }

retval = 0;
for (;;) {
@@ -582,16 +585,6 @@ static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
}
busy_flag = 0;

- /*
- * If this is the first loop and we have a timeout
- * given, then we convert to ktime_t and set the to
- * pointer to the expiry value.
- */
- if (end_time && !to) {
- expire = timespec64_to_ktime(*end_time);
- to = &expire;
- }
-
if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
to, slack))
timed_out = 1;
@@ -876,8 +869,11 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
timed_out = 1;
}

- if (end_time && !timed_out)
- slack = select_estimate_accuracy(end_time);
+ if (end_time && !timed_out) {
+ expire = timespec64_to_ktime(*end_time);
+ to = &expire;
+ slack = select_estimate_accuracy(expire);
+ }

for (;;) {
struct poll_list *walk;
@@ -930,16 +926,6 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
}
busy_flag = 0;

- /*
- * If this is the first loop and we have a timeout
- * given, then we convert to ktime_t and set the to
- * pointer to the expiry value.
- */
- if (end_time && !to) {
- expire = timespec64_to_ktime(*end_time);
- to = &expire;
- }
-
if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
timed_out = 1;
}
diff --git a/include/linux/poll.h b/include/linux/poll.h
index 1cdc32b1f1b0..d0f21eb19257 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -112,7 +112,7 @@ struct poll_wqueues {

extern void poll_initwait(struct poll_wqueues *pwq);
extern void poll_freewait(struct poll_wqueues *pwq);
-extern u64 select_estimate_accuracy(struct timespec64 *tv);
+extern u64 select_estimate_accuracy(ktime_t timeout);

#define MAX_INT64_SECONDS (((s64)(~((u64)0)>>1)/HZ)-1)

--
2.23.0