netdev - Re: [PATCH 1/1] netstamp_needed shouldn't be jump_label

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Date:	Tue, 29 Nov 2011 10:03:03 +0100
From:	"Igor Maravić" <igorm@....rs>
To:	"Eric Dumazet" <eric.dumazet@...il.com>
Cc:	igorm@....rs, netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] netstamp_needed shouldn't be jump_label_key

>
> Could you test following patch ?
>

I've just put it to compile. I'l let you know soon as it finishes compiling.

I have one proposition for your patch. To put WARN_ON before in ifdef endif,
because we don't needed if we don't have HAVE_JUMP_LABEL, and also to check it
before using jump_label_dec.

Also I have few questions :)

First - why can't we use spin_lock on jump_label?

I know that You said that is because we are using mutex_lock in
arch_jump_label_transform() or text_poke_smp(), but I don't see why couldn't
we use mutex_lock inside spin_lock.

To me using spin_lock_irqsave and spin_lock_irqrestore does sound like as most logical solution.
With that lock, we would be sure that our mutex_lock in arch_jump_label_transform() or text_poke_smp()
isn't going to be interrupted.
Please correct if I'm wrong.

Also I saw that you put calling of net_enable_timestamp outside of spin_lock_bh
Why?

BR
Igor

[PATCH 1/1] jump_label warning if_interrupt

Move warning on the top of function net_enable_timestamp,
so we would be also warn if we are going to jump_label_dec in interrupt

Signed-off-by: Igor Maravic <igorm@....rs>

:100644 100644 45eab03... ef23cf7... M	net/core/dev.c

diff --git a/net/core/dev.c b/net/core/dev.c
index 45eab03..ef23cf7 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1453,6 +1453,7 @@ void net_enable_timestamp(void)
 {
 #ifdef HAVE_JUMP_LABEL
 	int deferred = atomic_xchg(&netstamp_needed_deferred, 0);
+	WARN_ON(in_interrupt());

 	if (deferred) {
 		while (--deferred)
@@ -1460,7 +1461,6 @@ void net_enable_timestamp(void)
 		return;
 	}
 #endif
-	WARN_ON(in_interrupt());
 	jump_label_inc(&netstamp_needed);
 }
 EXPORT_SYMBOL(net_enable_timestamp);
-- 
1.7.5.4

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