net: avoid calling sched_clock when LLS is off

Change Low Latency Sockets code for select and poll so that
when LLS is disabled sched_clock() is never called.

Also, avoid sending POLL_LL to sockets if disabled.

Reported-by: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 4 deletions

diff --git a/fs/select.c b/fs/select.c
index 79b876eb91da..36540754bad7 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -402,7 +402,7 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
         poll_table *wait;
         int retval, i, timed_out = 0;
         unsigned long slack = 0;
-        unsigned int ll_flag = POLL_LL;
+        unsigned int ll_flag = ll_get_flag();
         u64 ll_time = ll_end_time();
 
         rcu_read_lock();
@@ -497,7 +497,8 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
                         break;
                 }
 
-                if (can_ll && can_poll_ll(ll_time))
+                /* only if on, have sockets with POLL_LL and not out of time */
+                if (ll_flag && can_ll && can_poll_ll(ll_time))
                         continue;
 
                 /*
@@ -768,7 +769,7 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
         ktime_t expire, *to = NULL;
         int timed_out = 0, count = 0;
         unsigned long slack = 0;
-        unsigned int ll_flag = POLL_LL;
+        unsigned int ll_flag = ll_get_flag();
         u64 ll_time = ll_end_time();
 
         /* Optimise the no-wait case */
@@ -817,8 +818,10 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
                 if (count || timed_out)
                         break;
 
-                if (can_ll && can_poll_ll(ll_time))
+                /* only if on, have sockets with POLL_LL and not out of time */
+                if (ll_flag && can_ll && can_poll_ll(ll_time))
                         continue;
+
                 /*
                  * If this is the first loop and we have a timeout
                  * given, then we convert to ktime_t and set the to