netdev - [PATCH] use cond_resched() to replace udelay() when dump eeprom

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Message-Id: <1399878384-4690-1-git-send-email-acho@suse.com>
Date:	Mon, 12 May 2014 15:06:24 +0800
From:	"Cho, Yu-Chen" <acho@...e.com>
To:	netdev@...r.kernel.org
Cc:	bpoirier@...e.de
Subject: [PATCH] use cond_resched() to replace udelay() when dump eeprom

The loop in tg3_nvram_exec_cmd() will give up after about 100 msec per command,
it can loop for a long time.

For some test case , if we try to dump eeprom from tg3 interface,
what is UP but not running , NO-CARRIER (no cable), then the lock up occurs:

[<ffffffffa01def4a>] tg3_nvram_exec_cmd+0x3a/0x60 [tg3]
[<ffffffffa01e2982>] tg3_nvram_read+0x62/0x130 [tg3]
[<ffffffffa01e2a62>] tg3_nvram_read_be32+0x12/0x30 [tg3]
[<ffffffffa01e2b1d>] tg3_get_eeprom+0x9d/0x190 [tg3]
[<ffffffff81494cc2>] ethtool_get_any_eeprom+0xe2/0x170
[<ffffffff81496108>] dev_ethtool+0xd58/0x1a60
[<ffffffff814a43fb>] dev_ioctl+0x1ab/0x560
[<ffffffff8147782d>] sock_do_ioctl+0x3d/0x50
[<ffffffff81477c78>] sock_ioctl+0x1e8/0x2c0
[<ffffffff81197cc4>] do_vfs_ioctl+0x2d4/0x4b0
[<ffffffff81197f20>] SyS_ioctl+0x80/0xa0
[<ffffffff81581a7d>] system_call_fastpath+0x1a/0x1f
[<00007f6b6cbf4387>] 0x7f6b6cbf4386

Signed-off-by: Cho, Yu-Chen <acho@...e.com>
---
 drivers/net/ethernet/broadcom/tg3.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index e5d95c5..7dc8bb5 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -3232,7 +3232,9 @@ static int tg3_nvram_exec_cmd(struct tg3 *tp, u32 nvram_cmd)
 
 	tw32(NVRAM_CMD, nvram_cmd);
 	for (i = 0; i < NVRAM_CMD_TIMEOUT; i++) {
-		udelay(10);
+
+		cond_resched();
+
 		if (tr32(NVRAM_CMD) & NVRAM_CMD_DONE) {
 			udelay(10);
 			break;
-- 
1.8.4.5

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