From b773ad40aca5bd755ba886620842f16e8fef6d75 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Sun, 31 Aug 2008 08:16:57 -0700 Subject: select: add poll_select_set_timeout() and poll_select_copy_remaining() helpers This patch adds 2 helpers that will be used for the hrtimer based select/poll: poll_select_set_timeout() is a helper that takes a timeout (as a second, nanosecond pair) and turns that into a "struct timespec" that represents the absolute end time. This is a common operation in the many select() and poll() variants and needs various, common, sanity checks. poll_select_copy_remaining() is a helper that takes care of copying the remaining time to userspace, as select(), pselect() and ppoll() do. This function comes in both a natural and a compat implementation (due to datastructure differences). Signed-off-by: Thomas Gleixner Signed-off-by: Arjan van de Ven --- fs/select.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) (limited to 'fs/select.c') diff --git a/fs/select.c b/fs/select.c index da0e88201c3a..1180a6207789 100644 --- a/fs/select.c +++ b/fs/select.c @@ -130,6 +130,81 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, add_wait_queue(wait_address, &entry->wait); } +/** + * poll_select_set_timeout - helper function to setup the timeout value + * @to: pointer to timespec variable for the final timeout + * @sec: seconds (from user space) + * @nsec: nanoseconds (from user space) + * + * Note, we do not use a timespec for the user space value here, That + * way we can use the function for timeval and compat interfaces as well. + * + * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. + */ +int poll_select_set_timeout(struct timespec *to, long sec, long nsec) +{ + struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec}; + + if (!timespec_valid(&ts)) + return -EINVAL; + + /* Optimize for the zero timeout value here */ + if (!sec && !nsec) { + to->tv_sec = to->tv_nsec = 0; + } else { + ktime_get_ts(to); + *to = timespec_add_safe(*to, ts); + } + return 0; +} + +static int poll_select_copy_remaining(struct timespec *end_time, void __user *p, + int timeval, int ret) +{ + struct timespec rts; + struct timeval rtv; + + if (!p) + return ret; + + if (current->personality & STICKY_TIMEOUTS) + goto sticky; + + /* No update for zero timeout */ + if (!end_time->tv_sec && !end_time->tv_nsec) + return ret; + + ktime_get_ts(&rts); + rts = timespec_sub(*end_time, rts); + if (rts.tv_sec < 0) + rts.tv_sec = rts.tv_nsec = 0; + + if (timeval) { + rtv.tv_sec = rts.tv_sec; + rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; + + if (!copy_to_user(p, &rtv, sizeof(rtv))) + return ret; + + } else if (!copy_to_user(p, &rts, sizeof(rts))) + return ret; + + /* + * If an application puts its timeval in read-only memory, we + * don't want the Linux-specific update to the timeval to + * cause a fault after the select has completed + * successfully. However, because we're not updating the + * timeval, we can't restart the system call. + */ + +sticky: + if (ret == -ERESTARTNOHAND) + ret = -EINTR; + return ret; +} + + + #define FDS_IN(fds, n) (fds->in + n) #define FDS_OUT(fds, n) (fds->out + n) #define FDS_EX(fds, n) (fds->ex + n) -- cgit