pktgen: clean up ktime_t helpers

Some years ago, the ktime_t helper functions ktime_now() and ktime_lt()
have been introduced. Instead of defining them inside pktgen.c, they
should either use ktime_t library functions or, if not available, they
should be defined in ktime.h, so that also others can benefit from them.
ktime_compare() is introduced with a similar notion as in timespec_compare().

Change-Id: I3d092b737d46cf2368baf4101c852fe9a4db510f
Signed-off-by: Daniel Borkmann <daniel.borkmann@tik.ee.ethz.ch>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
iopoll: Make readl_poll_timeout() and friends preemption-safe

With the previous implementation, pre-emption was possible
between reading the register value and evaluating the break
condition for the timeout. If jiffies advanced sufficiently to
expire the timeout before the polling thread was rescheduled,
the macro would return -ETIMEDOUT incorrectly.

Fix this by re-reading the register value again after evaluating
the timeout condition as true.

Change-Id: I58a42798235db3606373a2f689f7d6c95475702e
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>
iopoll: Use ktime_get() instead of jiffies for timeout calculations

Presently, small timeout values will round up to 1 jiffy which,
on CONFIG_HZ=100 systems, corresponds to a full 10 milliseconds.
This is undesirable for drivers specifying timeouts of only a
few 10's of microseconds (which is common), since they may end
up tight-loop spinning for hundreds or thousands of times longer
than expected before reporting a timeout.

Additionally, jiffies cannot be reliably used with time_after()
when the value of jiffies is small (like 1). In rare but real
scenarios, jiffies may actually increment by more than 1 at a
time. Specifically, this will occur if interrupts are disabled
on for more than 1 jiffy (10 milliseconds for CONFIG_HZ=100) on
the CPU responsible for incrementing jiffies.

If interrupts are re-enabled on that CPU between the time the
iopoll code (on another CPU) calculates the timeout value of
jiffies and when the time_after() comparison is made, then the
iopoll APIs may return -ETIMEDOUT prematurely, even though the
specified timeout has not actually expired.

Using ktime_get() avoid this problem (which arguably also needs
a generic fix to avoid similar problems for other code which use
jiffies to calculate timeouts).

CRs-Fixed: 587801
Change-Id: I19150f41965b918c59c3fb98e29a8bd2e2c9609f
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>