Merge tag 'ratelimit.2025.05.25a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull rate-limit updates from Paul McKenney:
 "lib/ratelimit: Reduce false-positive and silent misses:

   - Reduce open-coded use of ratelimit_state structure fields.

   - Convert the ->missed field to atomic_t.

   - Count misses that are due to lock contention.

   - Eliminate jiffies=0 special case.

   - Reduce ___ratelimit() false-positive rate limiting (Petr Mladek).

   - Allow zero ->burst to hard-disable rate limiting.

   - Optimize away atomic operations when a miss is guaranteed.

   - Warn if ->interval or ->burst are negative (Petr Mladek).

   - Simplify the resulting code.

  A smoke test and stress test have been created, but they are not yet
  ready for mainline. With luck, we will offer them for the v6.17 merge
  window"

* tag 'ratelimit.2025.05.25a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  ratelimit: Drop redundant accesses to burst
  ratelimit: Use nolock_ret restructuring to collapse common case code
  ratelimit: Use nolock_ret label to collapse lock-failure code
  ratelimit: Use nolock_ret label to save a couple of lines of code
  ratelimit: Simplify common-case exit path
  ratelimit: Warn if ->interval or ->burst are negative
  ratelimit: Avoid atomic decrement under lock if already rate-limited
  ratelimit: Avoid atomic decrement if already rate-limited
  ratelimit: Don't flush misses counter if RATELIMIT_MSG_ON_RELEASE
  ratelimit: Force re-initialization when rate-limiting re-enabled
  ratelimit: Allow zero ->burst to disable ratelimiting
  ratelimit: Reduce ___ratelimit() false-positive rate limiting
  ratelimit: Avoid jiffies=0 special case
  ratelimit: Count misses due to lock contention
  ratelimit: Convert the ->missed field to atomic_t
  drm/amd/pm: Avoid open-coded use of ratelimit_state structure's internals
  drm/i915: Avoid open-coded use of ratelimit_state structure's ->missed field
  random: Avoid open-coded use of ratelimit_state structure's ->missed field
  ratelimit: Create functions to handle ratelimit_state internals

2 files changed, 35 insertions, 7 deletions

diff --git a/include/linux/ratelimit.h b/include/linux/ratelimit.h
index b17e0cd0a30c..7aaad158ee37 100644
--- a/include/linux/ratelimit.h
+++ b/include/linux/ratelimit.h
@@ -22,16 +22,43 @@ static inline void ratelimit_default_init(struct ratelimit_state *rs)
 					DEFAULT_RATELIMIT_BURST);
 }
 
+static inline void ratelimit_state_inc_miss(struct ratelimit_state *rs)
+{
+	atomic_inc(&rs->missed);
+}
+
+static inline int ratelimit_state_get_miss(struct ratelimit_state *rs)
+{
+	return atomic_read(&rs->missed);
+}
+
+static inline int ratelimit_state_reset_miss(struct ratelimit_state *rs)
+{
+	return atomic_xchg_relaxed(&rs->missed, 0);
+}
+
+static inline void ratelimit_state_reset_interval(struct ratelimit_state *rs, int interval_init)
+{
+	unsigned long flags;
+
+	raw_spin_lock_irqsave(&rs->lock, flags);
+	rs->interval = interval_init;
+	rs->flags &= ~RATELIMIT_INITIALIZED;
+	atomic_set(&rs->rs_n_left, rs->burst);
+	ratelimit_state_reset_miss(rs);
+	raw_spin_unlock_irqrestore(&rs->lock, flags);
+}
+
 static inline void ratelimit_state_exit(struct ratelimit_state *rs)
 {
+	int m;
+
 	if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE))
 		return;
 
-	if (rs->missed) {
-		pr_warn("%s: %d output lines suppressed due to ratelimiting\n",
-			current->comm, rs->missed);
-		rs->missed = 0;
-	}
+	m = ratelimit_state_reset_miss(rs);
+	if (m)
+		pr_warn("%s: %d output lines suppressed due to ratelimiting\n", current->comm, m);
 }
 
 static inline void
diff --git a/include/linux/ratelimit_types.h b/include/linux/ratelimit_types.h
index 765232ce0b5e..b19c4354540a 100644
--- a/include/linux/ratelimit_types.h
+++ b/include/linux/ratelimit_types.h
@@ -11,14 +11,15 @@
 
 /* issue num suppressed message on exit */
 #define RATELIMIT_MSG_ON_RELEASE	BIT(0)
+#define RATELIMIT_INITIALIZED		BIT(1)
 
 struct ratelimit_state {
 	raw_spinlock_t	lock;		/* protect the state */
 
 	int		interval;
 	int		burst;
-	int		printed;
-	int		missed;
+	atomic_t	rs_n_left;
+	atomic_t	missed;
 	unsigned int	flags;
 	unsigned long	begin;
 };