2 files changed, 10 insertions, 11 deletions

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index a478c8eb8479..5b49d41868c8 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -35,7 +35,7 @@ struct srcu_struct_array {
 };
 
 /* Bit definitions for field ->c above and ->snap below. */
-#define SRCU_USAGE_BITS         2
+#define SRCU_USAGE_BITS         1
 #define SRCU_REF_MASK           (ULONG_MAX >> SRCU_USAGE_BITS)
 #define SRCU_USAGE_COUNT        (SRCU_REF_MASK + 1)
 
diff --git a/kernel/srcu.c b/kernel/srcu.c
index 17e95bcc901c..43f1d61e513e 100644
--- a/kernel/srcu.c
+++ b/kernel/srcu.c
@@ -138,14 +138,14 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx)
 
         /*
          * Now, we check the ->snap array that srcu_readers_active_idx()
-         * filled in from the per-CPU counter values.  Since both
-         * __srcu_read_lock() and __srcu_read_unlock() increment the
-         * upper bits of the per-CPU counter, an increment/decrement
-         * pair will change the value of the counter.  Since there is
-         * only one possible increment, the only way to wrap the counter
-         * is to have a huge number of counter decrements, which requires
-         * a huge number of tasks and huge SRCU read-side critical-section
-         * nesting levels, even on 32-bit systems.
+         * filled in from the per-CPU counter values. Since
+         * __srcu_read_lock() increments the upper bits of the per-CPU
+         * counter, an increment/decrement pair will change the value
+         * of the counter.  Since there is only one possible increment,
+         * the only way to wrap the counter is to have a huge number of
+         * counter decrements, which requires a huge number of tasks and
+         * huge SRCU read-side critical-section nesting levels, even on
+         * 32-bit systems.
          *
          * All of the ways of confusing the readings require that the scan
          * in srcu_readers_active_idx() see the read-side task's decrement,
@@ -234,8 +234,7 @@ void __srcu_read_unlock(struct srcu_struct *sp, int idx)
 {
         preempt_disable();
         smp_mb(); /* C */  /* Avoid leaking the critical section. */
-        ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) +=
-                SRCU_USAGE_COUNT - 1;
+        ACCESS_ONCE(this_cpu_ptr(sp->per_cpu_ref)->c[idx]) -= 1;
         preempt_enable();
 }
 EXPORT_SYMBOL_GPL(__srcu_read_unlock);