[PATCH net-next v2] 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 <dvyukov@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Fixes: 5aa3afe107d9 ("net: make unregister netdev warning timeout configurable")
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes since v1:
 - fix merge issue related to refcnt check
---
 Documentation/admin-guide/sysctl/net.rst | 2 +-
 net/core/dev.c                           | 2 +-
 net/core/sysctl_net_core.c               | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst
index 2090bfc69aa50..c941b214e0b7f 100644
--- a/Documentation/admin-guide/sysctl/net.rst
+++ b/Documentation/admin-guide/sysctl/net.rst

@@ -320,7 +320,7 @@ 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.
+Default value is 10, minimum 1, maximum 3600.
 
 optmem_max
 ----------

diff --git a/net/core/dev.c b/net/core/dev.c
index 4bb6dcdbed8b8..7bb00b8b86c64 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -10431,7 +10431,7 @@ static void netdev_wait_allrefs(struct net_device *dev)
 
 		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",

diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index d84c8a1b280e2..c8496c1142c9d 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c

@@ -577,7 +577,7 @@ static struct ctl_table net_core_table[] = {
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec_minmax,
-		.extra1		= SYSCTL_ZERO,
+		.extra1		= SYSCTL_ONE,
 		.extra2		= &int_3600,
 	},
 	{ }

base-commit: 84c7f6c33f42a12eb036ebf0f0e3670799304120
-- 
2.31.0.291.g576ba9dcdaf-goog

On 3/25/21 3:52 PM, Dmitry Vyukov wrote:

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 <dvyukov@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Fixes: 5aa3afe107d9 ("net: make unregister netdev warning timeout configurable")
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes since v1:
 - fix merge issue related to refcnt check

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks !

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Thu, 25 Mar 2021 15:52:45 +0100 you wrote:

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".

[...]

Here is the summary with links:
  - [net-next,v2] net: change netdev_unregister_timeout_secs min value to 1
    https://git.kernel.org/netdev/net-next/c/6c996e19949b

You are awesome, thank you!
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