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Date: Wed, 07 Nov 2007 14:45:18 -0800
From: "Kok, Auke" <auke-jan.h.kok@...el.com>
To: Linas Vepstas <linas@...tin.ibm.com>
CC: wenxiong@...ibm.com, e1000-devel@...ts.sourceforge.net,
"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
john.ronciak@...el.com, jeffrey.t.kirsher@...el.com,
Jeff Garzik <jeff@...zik.org>, NetDev <netdev@...r.kernel.org>,
'Stephen Hemminger' <shemminger@...ux-foundation.org>
Subject: Re: [PATCH 2/2]: e1000: avoid lockup durig error recovery
[adding netdev, jeff G to the Cc]
Linas Vepstas wrote:
> On Wed, Nov 07, 2007 at 01:50:17PM -0800, Kok, Auke wrote:
>> Linas Vepstas wrote:
>>> If a PCI bus error is encountered during device open, the
>>> error recovery routines will attempt to close the device.
>>> If napi has not yet been enabled, the napi disable in the
>>> close will hang.
>>>
>>> Signed-off-by: Linas Vepstas <linas@...tin.ibm.com>
>>>
>>> ----
>>> The "elegence" of this solution is arguable: one could
>>> say its "better" to perform this check in e1000_down().
>>> However, doing so will disrupt a commonly used path,
>>> whereas here, the hack is in the infrequently used
>>> error path, and thus less intrusive.
>>>
>>> drivers/net/e1000/e1000_main.c | 9 ++++++++-
>>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> Index: linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000_main.c
>>> ===================================================================
>>> --- linux-2.6.23-rc8-mm1.orig/drivers/net/e1000/e1000_main.c 2007-11-07 15:04:45.000000000 -0600
>>> +++ linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000_main.c 2007-11-07 15:04:52.000000000 -0600
>>> @@ -5268,8 +5268,15 @@ static pci_ers_result_t e1000_io_error_d
>>>
>>> netif_device_detach(netdev);
>>>
>>> - if (netif_running(netdev))
>>> + if (netif_running(netdev)) {
>>> +#ifdef CONFIG_E1000_NAPI
>>> + /* e1000_down will spinlock in napi_disable() if we
>>> + * catch an error before napi_enable() was called. */
>>> + if (test_bit(NAPI_STATE_SCHED, &adapter->napi.state))
>>> + napi_enable(&adapter->napi);
>>> +#endif
>>> e1000_down(adapter);
>>> + }
>>> pci_disable_device(pdev);
>>>
>>> /* Request a slot slot reset. */
>> I think this is OK, but it's quite awful looking if you ask me.
>
> Yeah, ...
>
> There are several alternatives: below are two. If you
> find one to be more appealing.. could you use it? Consider them
> to be "signed-off-by"; I have not actually compiled or tested
> either of them.
I'm not a particular fan of putting extra state tracking in the driver for
something we could extract from the napi subsystem already.
Jeff, Stephen, can't we have a generic napi_enabled() inline in netdevice.h that
tests for NAPI_STATE_SCHED ?
I wonder if there isn't something in the PCI error recovery missing the point and
we can solve this problem better for all drivers somehow.
Auke
>
>
> drivers/net/e1000/e1000_main.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000_main.c
> ===================================================================
> --- linux-2.6.23-rc8-mm1.orig/drivers/net/e1000/e1000_main.c 2007-11-07 16:11:36.000000000 -0600
> +++ linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000_main.c 2007-11-07 16:15:17.000000000 -0600
> @@ -633,7 +633,11 @@ e1000_down(struct e1000_adapter *adapter
> set_bit(__E1000_DOWN, &adapter->flags);
>
> #ifdef CONFIG_E1000_NAPI
> - napi_disable(&adapter->napi);
> + /* napi_disable() will spinlock if we are in the
> + * pci error recovery path, and caught a pci
> + * error before napi_enable() was called. */
> + if (!test_bit(NAPI_STATE_SCHED, &adapter->napi.state))
> + napi_disable(&adapter->napi);
> #endif
> e1000_irq_disable(adapter);
>
> and here's another:
>
> drivers/net/e1000/e1000.h | 1 +
> drivers/net/e1000/e1000_main.c | 7 ++++++-
> 2 files changed, 7 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000.h
> ===================================================================
> --- linux-2.6.23-rc8-mm1.orig/drivers/net/e1000/e1000.h 2007-09-26 15:06:56.000000000 -0500
> +++ linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000.h 2007-11-07 16:19:16.000000000 -0600
> @@ -301,6 +301,7 @@ struct e1000_adapter {
> struct e1000_rx_ring *rx_ring; /* One per active queue */
> #ifdef CONFIG_E1000_NAPI
> struct napi_struct napi;
> + int napi_enabled;
> struct net_device *polling_netdev; /* One per active queue */
> #endif
> int num_tx_queues;
> Index: linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000_main.c
> ===================================================================
> --- linux-2.6.23-rc8-mm1.orig/drivers/net/e1000/e1000_main.c 2007-11-07 16:16:11.000000000 -0600
> +++ linux-2.6.23-rc8-mm1/drivers/net/e1000/e1000_main.c 2007-11-07 16:22:30.000000000 -0600
> @@ -545,6 +545,7 @@ int e1000_up(struct e1000_adapter *adapt
>
> #ifdef CONFIG_E1000_NAPI
> napi_enable(&adapter->napi);
> + adapter->napi_enabled = 1;
> #endif
> e1000_irq_enable(adapter);
>
> @@ -633,7 +634,10 @@ e1000_down(struct e1000_adapter *adapter
> set_bit(__E1000_DOWN, &adapter->flags);
>
> #ifdef CONFIG_E1000_NAPI
> - napi_disable(&adapter->napi);
> + if (adapter->napi_enabled) {
> + napi_disable(&adapter->napi);
> + adapter->napi_enabled = 0;
> + }
> #endif
> e1000_irq_disable(adapter);
>
> @@ -1437,6 +1441,7 @@ e1000_open(struct net_device *netdev)
>
> #ifdef CONFIG_E1000_NAPI
> napi_enable(&adapter->napi);
> + adapter->napi_enabled = 1;
> #endif
>
> e1000_irq_enable(adapter);
-
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