// 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 separately 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 = 0;

        /*
         * Zero interval says never limit, otherwise, non-positive burst
         * says always limit.
         */
        if (interval <= 0 || burst <= 0) {
                WARN_ONCE(interval < 0 || burst < 0, "Negative interval (%d) or burst (%d): Uninitialized ratelimit_state structure?\n", interval, burst);
                ret = interval == 0 || burst > 0;
                if (!(READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED) || (!interval && !burst) ||
                    !raw_spin_trylock_irqsave(&rs->lock, flags))
                        goto nolock_ret;

                /* Force re-initialization once re-enabled. */
                rs->flags &= ~RATELIMIT_INITIALIZED;
                goto unlock_ret;
        }

        /*
         * If we contend on this state's lock then just check if
         * the current burst is used or not. It might cause
         * false positive when we are past the interval and
         * the current lock owner is just about to reset it.
         */
        if (!raw_spin_trylock_irqsave(&rs->lock, flags)) {
                if (READ_ONCE(rs->flags) & RATELIMIT_INITIALIZED &&
                    atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0)
                        ret = 1;
                goto nolock_ret;
        }

        if (!(rs->flags & RATELIMIT_INITIALIZED)) {
                rs->begin = jiffies;
                rs->flags |= RATELIMIT_INITIALIZED;
                atomic_set(&rs->rs_n_left, rs->burst);
        }

        if (time_is_before_jiffies(rs->begin + interval)) {
                int m;

                /*
                 * Reset rs_n_left ASAP to reduce false positives
                 * in parallel calls, see above.
                 */
                atomic_set(&rs->rs_n_left, rs->burst);
                rs->begin = jiffies;

                if (!(rs->flags & RATELIMIT_MSG_ON_RELEASE)) {
                        m = ratelimit_state_reset_miss(rs);
                        if (m) {
                                printk_deferred(KERN_WARNING
                                                "%s: %d callbacks suppressed\n", func, m);
                        }
                }
        }

        /* Note that the burst might be taken by a parallel call. */
        if (atomic_read(&rs->rs_n_left) > 0 && atomic_dec_return(&rs->rs_n_left) >= 0)
                ret = 1;

unlock_ret:
        raw_spin_unlock_irqrestore(&rs->lock, flags);

nolock_ret:
        if (!ret)
                ratelimit_state_inc_miss(rs);

        return ret;
}
EXPORT_SYMBOL(___ratelimit);