net: change netdev_unregister_timeout_secs min value to 1

netdev_unregister_timeout_secs=0 can lead to printing the
"waiting for dev to become free" message every jiffy.
This is too frequent and unnecessary.
Set the min value to 1 second.

Also fix the merge issue introduced by
"net: make unregister netdev warning timeout configurable":
it changed "refcnt != 1" to "refcnt".

Signed-off-by: Dmitry Vyukov <[e-mail]>
Suggested-by: Eric Dumazet <[e-mail]>
Fixes: 5aa3afe107d9 ("net: make unregister netdev warning timeout configurable")
Cc: [e-mail]
Cc: [e-mail]
Reviewed-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/admin-guide/sysctl/net.rst

···
 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.
+Default value is 10, minimum 1, maximum 3600.
 
 optmem_max
 ----------

net/core/dev.c

···
 
 		refcnt = netdev_refcnt_read(dev);
 
-		if (refcnt &&
+		if (refcnt != 1 &&
 		    time_after(jiffies, warning_time +
 			       netdev_unregister_timeout_secs * HZ)) {
 			pr_emerg("unregister_netdevice: waiting for %s to become free. Usage count = %d\n",

net/core/sysctl_net_core.c

···
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
+		.extra1		= SYSCTL_ONE,
 		.extra2		= &int_3600,
 	},
 	{ }