srcutiny: Mark read-side data races

This commit marks some interrupt-induced read-side data races in
__srcu_read_lock(), __srcu_read_unlock(), and srcu_torture_stats_print().

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 0e0cf4d..6cfaa0a 100644 (file)
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -61,7 +61,7 @@ static inline int __srcu_read_lock(struct srcu_struct *ssp)
        int idx;
 
        idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
-       WRITE_ONCE(ssp->srcu_lock_nesting[idx], ssp->srcu_lock_nesting[idx] + 1);
+       WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
        return idx;
 }
 
@@ -81,11 +81,11 @@ static inline void srcu_torture_stats_print(struct srcu_struct *ssp,
 {
        int idx;
 
-       idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
+       idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1;
        pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
                 tt, tf, idx,
-                READ_ONCE(ssp->srcu_lock_nesting[!idx]),
-                READ_ONCE(ssp->srcu_lock_nesting[idx]));
+                data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])),
+                data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])));
 }
 
 #endif

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 26344dc..a0ba2ed 100644 (file)
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -96,7 +96,7 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
  */
 void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
 {
-       int newval = ssp->srcu_lock_nesting[idx] - 1;
+       int newval = READ_ONCE(ssp->srcu_lock_nesting[idx]) - 1;
 
        WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval);
        if (!newval && READ_ONCE(ssp->srcu_gp_waiting))