netdev_wait_allrefs() issues a warning if refcount does not drop to 0 after 10 seconds. While 10 second wait generally should not happen under normal workload in normal environment, it seems to fire falsely very often during fuzzing and/or in qemu emulation (~10x slower). At least it's not possible to understand if it's really a false positive or not. Automated testing generally bumps all timeouts to very high values to avoid flake failures. Add net.core.netdev_unregister_timeout_secs sysctl to make the timeout configurable for automated testing systems. Lowering the timeout may also be useful for e.g. manual bisection. The default value matches the current behavior.
Signed-off-by: Dmitry Vyukov <dvyu...@google.com> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=211877 Cc: net...@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- Changes since v1: - use sysctl instead of a config --- Documentation/admin-guide/sysctl/net.rst | 11 +++++++++++ include/linux/netdevice.h | 1 + net/core/dev.c | 6 +++++- net/core/sysctl_net_core.c | 10 ++++++++++ 4 files changed, 27 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst index f2ab8a5b6a4b8..2090bfc69aa50 100644 --- a/Documentation/admin-guide/sysctl/net.rst +++ b/Documentation/admin-guide/sysctl/net.rst @@ -311,6 +311,17 @@ permit to distribute the load on several cpus. If set to 1 (default), timestamps are sampled as soon as possible, before queueing. +netdev_unregister_timeout_secs +------------------------------ + +Unregister network device timeout in seconds. +This option controls the timeout (in seconds) used to issue a warning while +waiting for a network device refcount to drop to 0 during device +unregistration. A lower value may be useful during bisection to detect +a leaked reference faster. A larger value may be useful to prevent false +warnings on slow/loaded systems. +Default value is 10, minimum 0, maximum 3600. + optmem_max ---------- diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 87a5d186faff4..179c5693f5119 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -4611,6 +4611,7 @@ void dev_get_tstats64(struct net_device *dev, struct rtnl_link_stats64 *s); extern int netdev_max_backlog; extern int netdev_tstamp_prequeue; +extern int netdev_unregister_timeout_secs; extern int weight_p; extern int dev_weight_rx_bias; extern int dev_weight_tx_bias; diff --git a/net/core/dev.c b/net/core/dev.c index 0f72ff5d34ba0..7accbd4a3bec1 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10344,6 +10344,8 @@ int netdev_refcnt_read(const struct net_device *dev) } EXPORT_SYMBOL(netdev_refcnt_read); +int netdev_unregister_timeout_secs __read_mostly = 10; + #define WAIT_REFS_MIN_MSECS 1 #define WAIT_REFS_MAX_MSECS 250 /** @@ -10405,7 +10407,9 @@ static void netdev_wait_allrefs(struct net_device *dev) refcnt = netdev_refcnt_read(dev); - if (refcnt && time_after(jiffies, warning_time + 10 * HZ)) { + if (refcnt && + time_after(jiffies, warning_time + + netdev_unregister_timeout_secs * HZ)) { pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n", dev->name, refcnt); warning_time = jiffies; diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c index 4567de519603b..d84c8a1b280e2 100644 --- a/net/core/sysctl_net_core.c +++ b/net/core/sysctl_net_core.c @@ -24,6 +24,7 @@ static int two = 2; static int three = 3; +static int int_3600 = 3600; static int min_sndbuf = SOCK_MIN_SNDBUF; static int min_rcvbuf = SOCK_MIN_RCVBUF; static int max_skb_frags = MAX_SKB_FRAGS; @@ -570,6 +571,15 @@ static struct ctl_table net_core_table[] = { .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ONE, }, + { + .procname = "netdev_unregister_timeout_secs", + .data = &netdev_unregister_timeout_secs, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = &int_3600, + }, { } }; base-commit: e0c755a45f6fb6e81e3a62a94db0400ef0cdc046 -- 2.31.0.291.g576ba9dcdaf-goog
