srcu: Block less aggressively for expedited grace periods

[linux-2.6-microblaze.git] / kernel / rcu / srcutree.c

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 50ba70f..0db7873 100644 (file)
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -513,7 +513,7 @@ static bool srcu_readers_active(struct srcu_struct *ssp)
 
 #define SRCU_INTERVAL          1       // Base delay if no expedited GPs pending.
 #define SRCU_MAX_INTERVAL      10      // Maximum incremental delay from slow readers.
-#define SRCU_MAX_NODELAY_PHASE 1       // Maximum per-GP-phase consecutive no-delay instances.
+#define SRCU_MAX_NODELAY_PHASE 3       // Maximum per-GP-phase consecutive no-delay instances.
 #define SRCU_MAX_NODELAY       100     // Maximum consecutive no-delay instances.
 
 /*
@@ -522,16 +522,22 @@ static bool srcu_readers_active(struct srcu_struct *ssp)
  */
 static unsigned long srcu_get_delay(struct srcu_struct *ssp)
 {
+       unsigned long gpstart;
+       unsigned long j;
        unsigned long jbase = SRCU_INTERVAL;
 
        if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
                jbase = 0;
-       if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)))
-               jbase += jiffies - READ_ONCE(ssp->srcu_gp_start);
-       if (!jbase) {
-               WRITE_ONCE(ssp->srcu_n_exp_nodelay, READ_ONCE(ssp->srcu_n_exp_nodelay) + 1);
-               if (READ_ONCE(ssp->srcu_n_exp_nodelay) > SRCU_MAX_NODELAY_PHASE)
-                       jbase = 1;
+       if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq))) {
+               j = jiffies - 1;
+               gpstart = READ_ONCE(ssp->srcu_gp_start);
+               if (time_after(j, gpstart))
+                       jbase += j - gpstart;
+               if (!jbase) {
+                       WRITE_ONCE(ssp->srcu_n_exp_nodelay, READ_ONCE(ssp->srcu_n_exp_nodelay) + 1);
+                       if (READ_ONCE(ssp->srcu_n_exp_nodelay) > SRCU_MAX_NODELAY_PHASE)
+                               jbase = 1;
+               }
        }
        return jbase > SRCU_MAX_INTERVAL ? SRCU_MAX_INTERVAL : jbase;
 }