commit 493c8d8d3c2f710d47b2bdd6a8ea582a84c1cf72
Author: William Dauchy <w.dauchy@criteo.com>
Date:   Sat Dec 28 15:36:02 2019 +0100

    MINOR: config: disable busy polling on old processes
    
    in the context of seamless reload and busy polling, older processes will
    create unecessary cpu conflicts; we can assume there is no need for busy
    polling for old processes which are waiting to be terminated.
    
    This patch is not a bug fix itself but might be a good stability
    improvment when you are un the context of frequent seamless reloads with
    a high "hard-stop-after" value; for that reasons I think this patch
    should be backported in all 2.x versions.
    
    Signed-off-by: William Dauchy <w.dauchy@criteo.com>
    (cherry picked from commit 3894d97fb8b66e247c5a326c6b3aa75816c597dc)
    Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

diff --git a/doc/configuration.txt b/doc/configuration.txt
index d34ed808b..3f381e386 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -1436,6 +1436,10 @@ busy-polling
   prefixing it with the "no" keyword. It is ignored by the "select" and
   "poll" pollers.
 
+  This option is automatically disabled on old processes in the context of
+  seamless reload; it avoids too much cpu conflicts when multiple processes
+  stay around for some time waiting for the end of their current connections.
+
 max-spread-checks <delay in milliseconds>
   By default, haproxy tries to spread the start of health checks across the
   smallest health check interval of all the servers in a farm. The principle is
diff --git a/src/proxy.c b/src/proxy.c
index 7ba6b5839..1abd6654f 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -1117,6 +1117,8 @@ void soft_stop(void)
 	struct task *task;
 
 	stopping = 1;
+	/* disable busy polling to avoid cpu eating for the new process */
+	global.tune.options &= ~GTUNE_BUSY_POLLING;
 	if (tick_isset(global.hard_stop_after)) {
 		task = task_new(MAX_THREADS_MASK);
 		if (task) {