[PATCH -v2 net-next] net/core/dev.c: enable timestamp static key if CPU isolation is configured

From: Marcelo Tosatti
Date: Wed Feb 28 2024 - 08:31:15 EST



For systems that use CPU isolation (via nohz_full), creating or destroying
a socket with timestamping (SOCK_TIMESTAMPING_RX_SOFTWARE and
SOF_TIMESTAMPING_OPT_TX_SWHW) might cause a
static key to be enabled/disabled. This in turn causes undesired
IPIs to isolated CPUs.

So enable the static key unconditionally, if CPU isolation is enabled,
thus avoiding the IPIs.

Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

---
v2: mention SOF_TIMESTAMPING_OPT_TX_SWHW in the commit log (Willem de Bruijn / Paolo Abeni)

diff --git a/net/core/dev.c b/net/core/dev.c
index c588808be77f..15a32f5900e6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -155,6 +155,7 @@
#include <net/netdev_rx_queue.h>
#include <net/page_pool/types.h>
#include <net/page_pool/helpers.h>
+#include <linux/sched/isolation.h>

#include "dev.h"
#include "net-sysfs.h"
@@ -11851,3 +11852,14 @@ static int __init net_dev_init(void)
}

subsys_initcall(net_dev_init);
+
+static int __init net_dev_late_init(void)
+{
+ /* avoid static key IPIs to isolated CPUs */
+ if (housekeeping_enabled(HK_TYPE_MISC))
+ net_enable_timestamp();
+
+ return 0;
+}
+
+late_initcall(net_dev_late_init);