From 919067cc845f323a80b6fe987b64238bd82d309e Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 19 Mar 2021 10:39:33 -0700 Subject: net: add CONFIG_PCPU_DEV_REFCNT I was working on a syzbot issue, claiming one device could not be dismantled because its refcount was -1 unregister_netdevice: waiting for sit0 to become free. Usage count = -1 It would be nice if syzbot could trigger a warning at the time this reference count became negative. This patch adds CONFIG_PCPU_DEV_REFCNT options which defaults to per cpu variables (as before this patch) on SMP builds. v2: free_dev label in alloc_netdev_mqs() is moved to avoid a compiler warning (-Wunused-label), as reported by kernel test robot Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/Kconfig | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'net/Kconfig') diff --git a/net/Kconfig b/net/Kconfig index 0ead7ec0d2bd..9c456acc379e 100644 --- a/net/Kconfig +++ b/net/Kconfig @@ -245,6 +245,14 @@ source "net/l3mdev/Kconfig" source "net/qrtr/Kconfig" source "net/ncsi/Kconfig" +config PCPU_DEV_REFCNT + bool "Use percpu variables to maintain network device refcount" + depends on SMP + default y + help + network device refcount are using per cpu variables if this option is set. + This can be forced to N to detect underflows (with a performance drop). + config RPS bool depends on SMP && SYSFS -- cgit v1.2.3