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authorThomas Gleixner <tglx@linutronix.de>2008-08-31 08:16:57 -0700
committerArjan van de Ven <arjan@linux.intel.com>2008-09-05 21:34:59 -0700
commitb773ad40aca5bd755ba886620842f16e8fef6d75 (patch)
tree7065661f6559aff70244f2805ced48f894c9b38c /fs/select.c
parentdf0cc0539b4127bd02f64de2c335b4af1fdb3845 (diff)
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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 <tglx@linutronix.de> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Diffstat (limited to 'fs/select.c')
-rw-r--r--fs/select.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/fs/select.c b/fs/select.c
index da0e882..1180a62 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)