1 files changed, 76 insertions, 0 deletions
diff --git a/lib/ratelimit.c b/lib/ratelimit.c
new file mode 100644
index 0000000000..ce945c1798
--- /dev/null
+++ b/lib/ratelimit.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ratelimit.c - Do something with rate limit.
+ *
+ * Isolated from kernel/printk.c by Dave Young <hidave.darkstar@gmail.com>
+ *
+ * 2008-05-01 rewrite the function and use a ratelimit_state data struct as
+ * parameter. Now every user can use their own standalone ratelimit_state.
+ */
+
+#include <linux/ratelimit.h>
+#include <linux/jiffies.h>
+#include <linux/export.h>
+
+/*
+ * __ratelimit - rate limiting
+ * @rs: ratelimit_state data
+ * @func: name of calling function
+ *
+ * This enforces a rate limit: not more than @rs->burst callbacks
+ * in every @rs->interval
+ *
+ * RETURNS:
+ * 0 means callbacks will be suppressed.
+ * 1 means go ahead and do it.
+ */
+int ___ratelimit(struct ratelimit_state *rs, const char *func)
+{
+	/* Paired with WRITE_ONCE() in .proc_handler().
+	 * Changing two values seperately could be inconsistent
+	 * and some message could be lost.  (See: net_ratelimit_state).
+	 */
+	int interval = READ_ONCE(rs->interval);
+	int burst = READ_ONCE(rs->burst);
+	unsigned long flags;
+	int ret;
+
+	if (!interval)
+		return 1;
+
+	/*
+	 * If we contend on this state's lock then almost
+	 * by definition we are too busy to print a message,
+	 * in addition to the one that will be printed by
+	 * the entity that is holding the lock already:
+	 */
+	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
+		return 0;
+
+	if (!rs->begin)
+		rs->begin = jiffies;
+
+	if (time_is_before_jiffies(rs->begin + interval)) {
+		if (rs->missed) {
+			if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
+				printk_deferred(KERN_WARNING
+						"%s: %d callbacks suppressed\n",
+						func, rs->missed);
+				rs->missed = 0;
+			}
+		}
+		rs->begin   = jiffies;
+		rs->printed = 0;
+	}
+	if (burst && burst > rs->printed) {
+		rs->printed++;
+		ret = 1;
+	} else {
+		rs->missed++;
+		ret = 0;
+	}
+	raw_spin_unlock_irqrestore(&rs->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL(___ratelimit);