From: Howard Chu <hyc@openldap.org>
Date: Fri, 14 Oct 2022 14:19:22 +0000 (+0100)
Subject: ITS#9930 fix cn=config / write_waiter deadlock
X-Git-Tag: OPENLDAP_REL_ENG_2_5_14~59
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bf5607b462788697d8be997aa3c62a767e0fedc9;p=thirdparty%2Fopenldap.git

ITS#9930 fix cn=config / write_waiter deadlock

If a writer is blocked and a config pause is pending, just
close the blocked connection. Don't wait around for a slow
client to catch up.
---

diff --git a/servers/slapd/result.c b/servers/slapd/result.c
index 9da5e7e1d1..a50f66498e 100644
--- a/servers/slapd/result.c
+++ b/servers/slapd/result.c
@@ -354,9 +354,7 @@ static long send_ldap_ber(
 	conn->c_writers++;
 
 	while ( conn->c_writers > 0 && conn->c_writing ) {
-		ldap_pvt_thread_pool_idle( &connection_pool );
 		ldap_pvt_thread_cond_wait( &conn->c_write1_cv, &conn->c_write1_mutex );
-		ldap_pvt_thread_pool_unidle( &connection_pool );
 	}
 
 	/* connection was closed under us */
@@ -405,15 +403,21 @@ fail:
 			return -1;
 		}
 
+		/* if writer is blocked and we're waiting for a pool pause,
+		 * just drop this connection.
+		 */
+		if ( ldap_pvt_thread_pool_pausing( &connection_pool ) > 0 ) {
+			close_reason = "writer blocked and pool pause pending";
+			goto fail;
+		}
+
 		/* wait for socket to be write-ready */
 		do_resume = 1;
 		conn->c_writewaiter = 1;
 		ldap_pvt_thread_mutex_unlock( &conn->c_write1_mutex );
-		ldap_pvt_thread_pool_idle( &connection_pool );
 		slap_writewait_play( op );
 		err = slapd_wait_writer( conn->c_sd );
 		conn->c_writewaiter = 0;
-		ldap_pvt_thread_pool_unidle( &connection_pool );
 		ldap_pvt_thread_mutex_lock( &conn->c_write1_mutex );
 		/* 0 is timeout, so we close it.
 		 * -1 is an error, close it.