linux-kernel - [patch] forcedeth: fix the NAPI poll function

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Message-ID: <20071015223009.GA27425@elte.hu>
Date:	Tue, 16 Oct 2007 00:30:09 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	David Miller <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	shemminger@...ux-foundation.org, Jeff Garzik <jgarzik@...ox.com>
Subject: [patch] forcedeth: fix the NAPI poll function


* Ingo Molnar <mingo@...e.hu> wrote:

> > but this one should be inactive (not plugged into the network). 
> > Should i try to get a debug print out of the actual 'weight' and 
> > 'work' integers, and of the n->poll function address?
> 
> ok, i've added such a patch.
> 
> looking at the dev.c code - can napi_struct->weight be zero 
> legitimately? If yes then the 0 gets passed to the driver and the 
> driver would return 1 - violating the assertion.

update:

[  186.635916] WARNING: at net/core/dev.c:2166 net_rx_action()
[  186.641351]  [<c060d9f5>] net_rx_action+0x145/0x1b0
[  186.646191]  [<c011d752>] __do_softirq+0x42/0x90
[  186.650784]  [<c011d7c6>] do_softirq+0x26/0x30
[  186.655202]  [<c011db48>] local_bh_enable+0x48/0xa0
[  186.660055]  [<c06023e0>] lock_sock_nested+0xa0/0xc0
[  186.664995]  [<c065da16>] tcp_recvmsg+0x16/0xbc0
[  186.669588]  [<c013e94b>] __generic_file_aio_write_nolock+0x27b/0x520
[  186.676001]  [<c0601d75>] sock_common_recvmsg+0x45/0x70
[  186.681202]  [<c05ff5df>] sock_aio_read+0x11f/0x140
[  186.686054]  [<c015c086>] do_sync_read+0xc6/0x110
[  186.690735]  [<c012b9b0>] autoremove_wake_function+0x0/0x40
[  186.696280]  [<c060dcfc>] net_tx_action+0x3c/0xe0
[  186.700961]  [<c015c9c2>] vfs_read+0x132/0x140
[  186.705378]  [<c015cd41>] sys_read+0x41/0x70
[  186.709625]  [<c0102b66>] sysenter_past_esp+0x5f/0x89
[  186.714651]  =======================
[  186.718210] work: 65, weight: 64
[  186.721414] ->poll: (nv_napi_poll+0x0/0x760)

so nv_napi_poll() returned with 65. How is that possible? Ah ...:

              (rx_processed_cnt++ < limit)) {

that should be:

              (++rx_processed_cnt < limit)) {

right? Find the fix below.

	Ingo

-------------------->
Subject: forcedeth: fix the NAPI poll function
From: Ingo Molnar <mingo@...e.hu>

fix the forcedeth NAPI poll function to not emit this warning:

[  186.635916] WARNING: at net/core/dev.c:2166 net_rx_action()
[  186.641351]  [<c060d9f5>] net_rx_action+0x145/0x1b0
[  186.646191]  [<c011d752>] __do_softirq+0x42/0x90
[  186.650784]  [<c011d7c6>] do_softirq+0x26/0x30
[  186.655202]  [<c011db48>] local_bh_enable+0x48/0xa0
[  186.660055]  [<c06023e0>] lock_sock_nested+0xa0/0xc0
[  186.664995]  [<c065da16>] tcp_recvmsg+0x16/0xbc0
[  186.669588]  [<c013e94b>] __generic_file_aio_write_nolock+0x27b/0x520
[  186.676001]  [<c0601d75>] sock_common_recvmsg+0x45/0x70
[  186.681202]  [<c05ff5df>] sock_aio_read+0x11f/0x140
[  186.686054]  [<c015c086>] do_sync_read+0xc6/0x110
[  186.690735]  [<c012b9b0>] autoremove_wake_function+0x0/0x40
[  186.696280]  [<c060dcfc>] net_tx_action+0x3c/0xe0
[  186.700961]  [<c015c9c2>] vfs_read+0x132/0x140
[  186.705378]  [<c015cd41>] sys_read+0x41/0x70
[  186.709625]  [<c0102b66>] sysenter_past_esp+0x5f/0x89
[  186.714651]  =======================

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 drivers/net/forcedeth.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux/drivers/net/forcedeth.c
===================================================================
--- linux.orig/drivers/net/forcedeth.c
+++ linux/drivers/net/forcedeth.c
@@ -2274,7 +2274,7 @@ static int nv_rx_process(struct net_devi
 
 	while((np->get_rx.orig != np->put_rx.orig) &&
 	      !((flags = le32_to_cpu(np->get_rx.orig->flaglen)) & NV_RX_AVAIL) &&
-		(rx_processed_cnt++ < limit)) {
+		(++rx_processed_cnt < limit)) {
 
 		dprintk(KERN_DEBUG "%s: nv_rx_process: flags 0x%x.\n",
 					dev->name, flags);
@@ -2412,7 +2412,7 @@ static int nv_rx_process_optimized(struc
 
 	while((np->get_rx.ex != np->put_rx.ex) &&
 	      !((flags = le32_to_cpu(np->get_rx.ex->flaglen)) & NV_RX2_AVAIL) &&
-	      (rx_processed_cnt++ < limit)) {
+	      (++rx_processed_cnt < limit)) {
 
 		dprintk(KERN_DEBUG "%s: nv_rx_process_optimized: flags 0x%x.\n",
 					dev->name, flags);
-
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