hrtimer: fix signed/unsigned bug in slack estimator

the slack estimator used unsigned math; however for very short delay it's
possible that by the time you calculate the timeout, it's already passed and
you get a negative time/slack... in an unsigned variable... which then gets
turned into a 100 msec delay rather than zero.

This patch fixes this by using a signed typee in the right places.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/fs/select.c b/fs/select.c
index fdd8584e536d..448e44001286 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -41,9 +41,9 @@
  * better solutions..
  */
 
-static unsigned long __estimate_accuracy(struct timespec *tv)
+static long __estimate_accuracy(struct timespec *tv)
 {
-        unsigned long slack;
+        long slack;
         int divfactor = 1000;
 
         if (task_nice(current) > 0)
@@ -54,10 +54,13 @@ static unsigned long __estimate_accuracy(struct timespec *tv)
 
         if (slack > 100 * NSEC_PER_MSEC)
                 slack =  100 * NSEC_PER_MSEC;
+
+        if (slack < 0)
+                slack = 0;
         return slack;
 }
 
-static unsigned long estimate_accuracy(struct timespec *tv)
+static long estimate_accuracy(struct timespec *tv)
 {
         unsigned long ret;
         struct timespec now;
@@ -330,7 +333,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                 timed_out = 1;
         }
 
-        if (end_time)
+        if (end_time && !timed_out)
                 slack = estimate_accuracy(end_time);
 
         retval = 0;
@@ -656,7 +659,7 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
                 timed_out = 1;
         }
 
-        if (end_time)
+        if (end_time && !timed_out)
                 slack = estimate_accuracy(end_time);
 
         for (;;) {