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Subject[PATCH net-next -v3] net/core/dev.c: enable timestamp static key if CPU isolation is configured

For systems that use CPU isolation (via nohz_full), creating or destroying
a socket with timestamping (SOCK_TIMESTAMPING_RX_SOFTWARE) 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@redhat.com>

---
v2: mention SOF_TIMESTAMPING_OPT_TX_SWHW in the commit log (Willem de Bruijn / Paolo Abeni)
v3: SOF_TIMESTAMPING_OPT_TX_SWHW is irrelevant (Willem de Bruijn)

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);

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