From: Eric Dumazet <dada1@cosmosbay.com>
To: Marin Mitov <mitov@issp.bas.bg>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: Is netif_tx_lock() SMP PREEMPT safe?
Date: Fri, 15 Feb 2008 17:01:03 +0100 [thread overview]
Message-ID: <47B5B73F.9050904@cosmosbay.com> (raw)
In-Reply-To: <200802151725.05424.mitov@issp.bas.bg>
Marin Mitov a écrit :
> Hi all,
>
> As in: include/linux/netdevice.h (kernel-2.6.24.2) one finds:
>
> static inline void __netif_tx_lock(struct net_device *dev, int cpu)
> {
> spin_lock(&dev->_xmit_lock);
> dev->xmit_lock_owner = cpu;
> }
>
> static inline void netif_tx_lock(struct net_device *dev)
> {
> __netif_tx_lock(dev, smp_processor_id());
> }
>
> Does netif_tx_lock(struct net_device *dev) expands into:
>
> cpu = smp_processor_id();
> <preempt & shift to another cpu (bogus)>
> spin_lock(&dev->_xmit_lock);
> dev->xmit_lock_owner = cpu; /* cpu is not the lock owner */
>
> Or to:
>
> spin_lock(&dev->_xmit_lock);
> dev->xmit_lock_owner = smp_processor_id();
>
> which is correct?
>
>
Hi Marin
This expands to the first version, but netif_tx_lock() is allways called
with preemption disabled.
(Or checks in smp_processor_id() would just trigger)
Eric
(Cced netdev for network related stuff)
parent reply other threads:[~2008-02-15 16:01 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <200802151725.05424.mitov@issp.bas.bg>]
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