From: Bruce Allan <bruce.w.allan@intel.com>
Date: Tue, 29 Nov 2011 08:09:19 +0000 (+0000)
Subject: e1000e: hitting BUG_ON() from napi_enable
X-Git-Tag: v3.3-rc1~182^2~349^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5f4a780ddd453c4918555fed9d9c5f2d455a087d;p=pandora-kernel.git

e1000e: hitting BUG_ON() from napi_enable

Based on a patch from Mike McElroy created against the out-of-tree e1000e
driver:

Hitting the BUG_ON in napi_enable(). Code inspection shows that this can
only be triggered by calling napi_enable() twice without an intervening
napi_disable().

I saw the following sequence of events in the stack trace:

1) We simulated a cable pull using an Extreme switch.
2) e1000_tx_timeout() was entered.
3) e1000_reset_task() was called. Saw the message from e_err() in the
console log.
4) e1000_reinit_locked was called. This function calls e1000_down() and
e1000_up(). These functions call napi_disable() and napi_enable()
respectively.
5) Then on another thread, a monitor task saw carrier was down and executed
'ip set link down' and 'ip set link up' commands.
6) Saw the '_E1000_RESETTING'warning fron the e1000_close function.
7) Either the e1000_open() executed between the e1000_down() and e1000_up()
calls in step 4 or the e1000_open() call executed after the e1000_up()
call.  In either case, napi_enable() is called twice which triggers the
BUG_ON.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Cc: Mike McElroy <mike.mcelroy@stratus.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
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