[PARISC] Fix do_gettimeofday() hang

Apparently gettimeoffset can return small negative values (usually in
the 100us range).  If xtime.tv_nsec is accidentally less than this,
though (a fortunately unlikely event) it triggers the loop forever.

I've added a test and correct adjustment for this case.  It has a
warning printk in there which I'd like to leave for the time being
just in case this problem implicates some other part of the kernel.

Signed-off-by: James Bottomley <jejb@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 16 insertions, 2 deletions

diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
index 594930bc4bcf..eb35e1c0bb53 100644
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -157,8 +157,22 @@ do_gettimeofday (struct timeval *tv)
                 usec += (xtime.tv_nsec / 1000);
         } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
 
-        while (usec >= 1000000) {
-                usec -= 1000000;
+        if (unlikely(usec > LONG_MAX)) {
+                /* This can happen if the gettimeoffset adjustment is
+                 * negative and xtime.tv_nsec is smaller than the
+                 * adjustment */
+                printk(KERN_ERR "do_gettimeofday() spurious xtime.tv_nsec of %ld\n", usec);
+                usec += USEC_PER_SEC;
+                --sec;
+                /* This should never happen, it means the negative
+                 * time adjustment was more than a second, so there's
+                 * something seriously wrong */
+                BUG_ON(usec > LONG_MAX);
+        }
+
+
+        while (usec >= USEC_PER_SEC) {
+                usec -= USEC_PER_SEC;
                 ++sec;
         }