Fix problems about 32-bit ticks wraparound and unsigned long

conversion:
- The linux compat API layer casts the ticks to unsigned long which
might cause problems when the ticks value is negative.
- Guard against already expired ticks values, by checking if the
passed expiry tick is already elapsed.
- While at it avoid referring the address of an inlined function.

MFC after:	3 days
Sponsored by:	Mellanox Technologies

sys/ofed/include/linux/linux_compat.c

@@ -57,6 +57,7 @@
 #include <linux/io.h>
 #include <linux/vmalloc.h>
 #include <linux/netdevice.h>
+#include <linux/timer.h>
 
 #include <vm/vm_pager.h>
 
@@ -77,6 +78,8 @@ struct list_head pci_devices;
 struct net init_net;
 spinlock_t pci_lock;
 
+unsigned long linux_timer_hz_mask;
+
 int
 panic_cmp(struct rb_node *one, struct rb_node *two)
 {
@@ -724,6 +727,60 @@ kasprintf(gfp_t gfp, const char *fmt, ...)
 	return p;
 }
 
+static int
+linux_timer_jiffies_until(unsigned long expires)
+{
+	int delta = expires - jiffies;
+	/* guard against already expired values */
+	if (delta < 1)
+		delta = 1;
+	return (delta);
+}
+
+static void
+linux_timer_callback_wrapper(void *context)
+{
+	struct timer_list *timer;
+
+	timer = context;
+	timer->function(timer->data);
+}
+
+void
+mod_timer(struct timer_list *timer, unsigned long expires)
+{
+
+	timer->expires = expires;
+	callout_reset(&timer->timer_callout,		      
+	    linux_timer_jiffies_until(expires),
+	    &linux_timer_callback_wrapper, timer);
+}
+
+void
+add_timer(struct timer_list *timer)
+{
+
+	callout_reset(&timer->timer_callout,
+	    linux_timer_jiffies_until(timer->expires),
+	    &linux_timer_callback_wrapper, timer);
+}
+
+static void
+linux_timer_init(void *arg)
+{
+
+	/*
+	 * Compute an internal HZ value which can divide 2**32 to
+	 * avoid timer rounding problems when the tick value wraps
+	 * around 2**32:
+	 */
+	linux_timer_hz_mask = 1;
+	while (linux_timer_hz_mask < (unsigned long)hz)
+		linux_timer_hz_mask *= 2;
+	linux_timer_hz_mask--;
+}
+SYSINIT(linux_timer, SI_SUB_DRIVERS, SI_ORDER_FIRST, linux_timer_init, NULL);
+
 static void
 linux_compat_init(void)
 {

sys/ofed/include/linux/timer.h

@@ -27,7 +27,7 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #ifndef _LINUX_TIMER_H_
-#define _LINUX_TIMER_H_
+#define	_LINUX_TIMER_H_
 
 #include <linux/types.h>
 
@@ -36,20 +36,13 @@
 #include <sys/callout.h>
 
 struct timer_list {
-	struct callout	timer_callout;
-	void		(*function)(unsigned long);
-	unsigned long	data;
-	unsigned long	expires;
+	struct callout timer_callout;
+	void    (*function) (unsigned long);
+	unsigned long data;
+	unsigned long expires;
 };
 
-static inline void
-_timer_fn(void *context)
-{
-	struct timer_list *timer;
-
-	timer = context;
-	timer->function(timer->data);
-}
+extern unsigned long linux_timer_hz_mask;
 
 #define	setup_timer(timer, func, dat)					\
 do {									\
@@ -65,28 +58,15 @@ do {									\
 	callout_init(&(timer)->timer_callout, CALLOUT_MPSAFE);		\
 } while (0)
 
-#define	mod_timer(timer, exp)						\
-do {									\
-	(timer)->expires = (exp);					\
-	callout_reset(&(timer)->timer_callout, (exp) - jiffies,		\
-	    _timer_fn, (timer));					\
-} while (0)
-
-#define	add_timer(timer)						\
-	callout_reset(&(timer)->timer_callout,				\
-	    (timer)->expires - jiffies, _timer_fn, (timer))
+extern void mod_timer(struct timer_list *, unsigned long);
+extern void add_timer(struct timer_list *);
 
 #define	del_timer(timer)	callout_stop(&(timer)->timer_callout)
 #define	del_timer_sync(timer)	callout_drain(&(timer)->timer_callout)
-
 #define	timer_pending(timer)	callout_pending(&(timer)->timer_callout)
+#define	round_jiffies(j) \
+	((unsigned long)(((j) + linux_timer_hz_mask) & ~linux_timer_hz_mask))
+#define	round_jiffies_relative(j) \
+	round_jiffies(j)
 
-static inline unsigned long
-round_jiffies(unsigned long j)
-{
-	return roundup(j, hz);
-}
-
-#define round_jiffies_relative(j) round_jiffies(j)
-
-#endif /* _LINUX_TIMER_H_ */
+#endif					/* _LINUX_TIMER_H_ */