ratelimit.c

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/*
 * ratelimit.c - Do something with rate limit.
 *
 * Isolated from kernel/printk.c by Dave Young <[email protected]>
 *
 * 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.
 *
 * This file is released under the GPLv2.
 */

#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)
{
    unsigned long flags;
    int ret;

    if (!rs->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 + rs->interval)) {
        if (rs->missed)
            printk(KERN_WARNING "%s: %d callbacks suppressed\n",
                func, rs->missed);
        rs->begin   = 0;
        rs->printed = 0;
        rs->missed  = 0;
    }
    if (rs->burst && rs->burst > rs->printed) {
        rs->printed++;
        ret = 1;
    } else {
        rs->missed++;
        ret = 0;
    }
    raw_spin_unlock_irqrestore(&rs->lock, flags);

    return ret;
}
EXPORT_SYMBOL(___ratelimit);