forked from Minki/linux
net: make unregister netdev warning timeout configurable
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 <dvyukov@google.com> Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=211877 Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -311,6 +311,17 @@ permit to distribute the load on several cpus.
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If set to 1 (default), timestamps are sampled as soon as possible, before
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queueing.
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netdev_unregister_timeout_secs
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------------------------------
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Unregister network device timeout in seconds.
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This option controls the timeout (in seconds) used to issue a warning while
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waiting for a network device refcount to drop to 0 during device
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unregistration. A lower value may be useful during bisection to detect
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a leaked reference faster. A larger value may be useful to prevent false
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warnings on slow/loaded systems.
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Default value is 10, minimum 0, maximum 3600.
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optmem_max
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----------
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@ -4661,6 +4661,7 @@ void dev_get_tstats64(struct net_device *dev, struct rtnl_link_stats64 *s);
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extern int netdev_max_backlog;
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extern int netdev_tstamp_prequeue;
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extern int netdev_unregister_timeout_secs;
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extern int weight_p;
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extern int dev_weight_rx_bias;
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extern int dev_weight_tx_bias;
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@ -10322,6 +10322,8 @@ int netdev_refcnt_read(const struct net_device *dev)
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}
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EXPORT_SYMBOL(netdev_refcnt_read);
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int netdev_unregister_timeout_secs __read_mostly = 10;
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#define WAIT_REFS_MIN_MSECS 1
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#define WAIT_REFS_MAX_MSECS 250
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/**
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@ -10383,7 +10385,9 @@ static void netdev_wait_allrefs(struct net_device *dev)
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refcnt = netdev_refcnt_read(dev);
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if (refcnt != 1 && time_after(jiffies, warning_time + 10 * HZ)) {
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if (refcnt &&
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time_after(jiffies, warning_time +
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netdev_unregister_timeout_secs * HZ)) {
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pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",
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dev->name, refcnt);
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warning_time = jiffies;
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@ -24,6 +24,7 @@
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static int two = 2;
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static int three = 3;
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static int int_3600 = 3600;
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static int min_sndbuf = SOCK_MIN_SNDBUF;
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static int min_rcvbuf = SOCK_MIN_RCVBUF;
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static int max_skb_frags = MAX_SKB_FRAGS;
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@ -570,6 +571,15 @@ static struct ctl_table net_core_table[] = {
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.proc_handler = proc_dointvec_minmax,
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.extra1 = SYSCTL_ONE,
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},
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{
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.procname = "netdev_unregister_timeout_secs",
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.data = &netdev_unregister_timeout_secs,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = SYSCTL_ZERO,
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.extra2 = &int_3600,
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},
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{ }
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};
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