From: Christopher Faulet <cfaulet@haproxy.com>
Date: Wed, 28 Aug 2024 08:04:42 +0000 (+0200)
Subject: MEDIUM: bwlim: Use a read-lock on the sticky session to apply a shared limit
X-Git-Tag: v3.1-dev7~16
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f9adcdf039369cd9ae71023ccbb9c9a72993e454;p=thirdparty%2Fhaproxy.git

MEDIUM: bwlim: Use a read-lock on the sticky session to apply a shared limit

There is no reason to acquire a write-lock on the sticky session when a
shared limit is applied because only the frequency is updated. The sticky
session itself is not modified. We must just take care it is not removed in
the mean time. So a read-lock may be used instead.
---

diff --git a/src/flt_bwlim.c b/src/flt_bwlim.c
index 1d07598033..3c75b9bb0e 100644
--- a/src/flt_bwlim.c
+++ b/src/flt_bwlim.c
@@ -106,7 +106,7 @@ static int bwlim_apply_limit(struct filter *filter, struct channel *chn, unsigne
 		if (!ptr)
 			goto end;
 
-		HA_RWLOCK_WRLOCK(STK_SESS_LOCK, &st->ts->lock);
+		HA_RWLOCK_RDLOCK(STK_SESS_LOCK, &st->ts->lock);
 		bytes_rate = &stktable_data_cast(ptr, std_t_frqp);
 		period = conf->table.t->data_arg[type].u;
 		limit = conf->limit;
@@ -137,7 +137,7 @@ static int bwlim_apply_limit(struct filter *filter, struct channel *chn, unsigne
 	overshoot = freq_ctr_overshoot_period(bytes_rate, period, limit);
 	if (overshoot > 0) {
 		if (conf->flags & BWLIM_FL_SHARED)
-			HA_RWLOCK_WRUNLOCK(STK_SESS_LOCK, &st->ts->lock);
+			HA_RWLOCK_RDUNLOCK(STK_SESS_LOCK, &st->ts->lock);
 		wait = div64_32((uint64_t)(conf->min_size + overshoot) * period * users,
 				limit);
 		st->exp = tick_add(now_ms, (wait ? wait : 1));
@@ -178,7 +178,7 @@ static int bwlim_apply_limit(struct filter *filter, struct channel *chn, unsigne
 	}
 
 	if (conf->flags & BWLIM_FL_SHARED)
-		HA_RWLOCK_WRUNLOCK(STK_SESS_LOCK, &st->ts->lock);
+		HA_RWLOCK_RDUNLOCK(STK_SESS_LOCK, &st->ts->lock);
 
   end:
 	chn->analyse_exp = tick_first((tick_is_expired(chn->analyse_exp, now_ms) ? TICK_ETERNITY : chn->analyse_exp),