[PATCH 7/9] select: Use ktime_t in do_sys_poll() and do_poll()

Dmitry Safonov
2019-09-09T10:24:13Z

The plan is to store what's left of timeout in restart block as ktime_t
which will be used for futex() and nanosleep() timeouts too. That will
be a value to return with a new ptrace() request API.

Convert end_time argument of do_{sys_,}poll() functions to ktime_t as
a preparation ground for storing ktime_t inside restart_block.

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
fs/select.c | 47 +++++++++++++++++++++++------------------------
1 file changed, 23 insertions(+), 24 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index 262300e58370..4af88feaa2fe 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -854,25 +854,22 @@ static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
}

static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
- struct timespec64 *end_time)
+ ktime_t end_time)
{
poll_table* pt = &wait->pt;
- ktime_t expire, *to = NULL;
+ ktime_t *to = NULL;
int timed_out = 0, count = 0;
u64 slack = 0;
__poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
unsigned long busy_start = 0;

/* Optimise the no-wait case */
- if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
+ if (ktime_compare(ktime_get(), end_time) >= 0) {
pt->_qproc = NULL;
timed_out = 1;
- }
-
- if (end_time && !timed_out) {
- expire = timespec64_to_ktime(*end_time);
- to = &expire;
- slack = select_estimate_accuracy(expire);
+ } else {
+ to = &end_time;
+ slack = select_estimate_accuracy(end_time);
}

for (;;) {
@@ -936,7 +933,7 @@ static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
sizeof(struct pollfd))

static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
- struct timespec64 *end_time)
+ ktime_t end_time)
{
struct poll_wqueues table;
int err = -EFAULT, fdcount, len;
@@ -1004,16 +1001,15 @@ static long do_restart_poll(struct restart_block *restart_block)
{
struct pollfd __user *ufds = restart_block->poll.ufds;
int nfds = restart_block->poll.nfds;
- struct timespec64 *to = NULL, end_time;
+ ktime_t timeout = 0;
int ret;

if (restart_block->poll.has_timeout) {
- end_time.tv_sec = restart_block->poll.tv_sec;
- end_time.tv_nsec = restart_block->poll.tv_nsec;
- to = &end_time;
+ timeout = ktime_set(restart_block->poll.tv_sec,
+ restart_block->poll.tv_nsec);
}

- ret = do_sys_poll(ufds, nfds, to);
+ ret = do_sys_poll(ufds, nfds, timeout);

if (ret == -ERESTARTNOHAND) {
restart_block->fn = do_restart_poll;
@@ -1025,16 +1021,17 @@ static long do_restart_poll(struct restart_block *restart_block)
SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
int, timeout_msecs)
{
- struct timespec64 end_time, *to = NULL;
+ struct timespec64 end_time;
+ ktime_t timeout = 0;
int ret;

if (timeout_msecs >= 0) {
- to = &end_time;
- poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
+ poll_select_set_timeout(&end_time, timeout_msecs / MSEC_PER_SEC,
NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
+ timeout = timespec64_to_ktime(end_time);
}

- ret = do_sys_poll(ufds, nfds, to);
+ ret = do_sys_poll(ufds, nfds, timeout);

if (ret == -ERESTARTNOHAND) {
struct restart_block *restart_block;
@@ -1060,7 +1057,8 @@ static int do_sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
void __user *tsp, const void __user *sigmask,
size_t sigsetsize, enum poll_time_type pt_type)
{
- struct timespec64 ts, end_time, *to = NULL;
+ struct timespec64 ts, *to = NULL;
+ ktime_t timeout = 0;
int ret;

if (tsp) {
@@ -1078,9 +1076,10 @@ static int do_sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
return -ENOSYS;
}

- to = &end_time;
- if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
+ to = &ts;
+ if (poll_select_set_timeout(&ts, ts.tv_sec, ts.tv_nsec))
return -EINVAL;
+ timeout = timespec64_to_ktime(ts);
}

if (!in_compat_syscall())
@@ -1091,8 +1090,8 @@ static int do_sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
if (ret)
return ret;

- ret = do_sys_poll(ufds, nfds, to);
- return poll_select_finish(&end_time, tsp, pt_type, ret);
+ ret = do_sys_poll(ufds, nfds, timeout);
+ return poll_select_finish(to, tsp, pt_type, ret);
}

SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
--
2.23.0