linux-kernel - Re: [PATCH] [RFC] EEE PC hangs when booting off battery

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Date:	Wed, 29 Apr 2009 12:14:33 +0100
From:	Alan Jenkins <alan-jenkins@...fmail.co.uk>
To:	John Linville <linville@...driver.com>
CC:	Johannes Berg <johannes@...solutions.net>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [PATCH] [RFC] EEE PC hangs when booting off battery

Alan Jenkins wrote:
> Johannes Berg wrote:
>   
>> That doesn't seem relevant, this just does some initialisation. However,
>> you definitely missed adding a call to wep_free().
>>   
>>     
>
> Hah, I should have realized something was wrong when I noticed I was
> removing more lines that I added. 
>
> The crypto init does cause the module load:
>
> wait_for_completion
> call_usermodehelper_exec
> __request_module
> crypto_larval_lookup
> ? extract_entropy
> crypto_alg_mod_lookup
> crypto_alloc_base
> ieee80211_wep_init
> ieee80211_register_hw
>   

Here's a corrected patch complete with changelog.  If there are no other
problems with it, can you please  apply this for 2.6.30 to keep my EeePC
regression-free?

Thanks
Alan

------>
>From c5e9dc036247e70956d1a28e8850c3810385dda0 Mon Sep 17 00:00:00 2001
From: Alan Jenkins <alan-jenkins@...fmail.co.uk>
Date: Wed, 29 Apr 2009 11:41:24 +0100
Subject: [PATCH] mac80211: fix modprobe deadlock by not calling wep_init under rtnl_lock

 - ieee80211_wep_init(), which is called with rtnl_lock held, blocks in
   request_module() [waiting for modprobe to load a crypto module].

 - modprobe blocks in a call to flush_workqueue(), when it closes a TTY
   [presumably when it exits].

 - The workqueue item linkwatch_event() blocks on rtnl_lock.

There's no reason for wep_init() to be called with rtnl_lock held, so
just move it outside the critical section.

Signed-off-by: Alan Jenkins <alan-jenkins@...fmail.co.uk>
---
 net/mac80211/main.c |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index fbcbed6..00968c2 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -909,6 +909,13 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 	if (result < 0)
 		goto fail_sta_info;
 
+	result = ieee80211_wep_init(local);
+	if (result < 0) {
+		printk(KERN_DEBUG "%s: Failed to initialize wep: %d\n",
+		       wiphy_name(local->hw.wiphy), result);
+		goto fail_wep;
+	}
+
 	rtnl_lock();
 	result = dev_alloc_name(local->mdev, local->mdev->name);
 	if (result < 0)
@@ -930,14 +937,6 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 		goto fail_rate;
 	}
 
-	result = ieee80211_wep_init(local);
-
-	if (result < 0) {
-		printk(KERN_DEBUG "%s: Failed to initialize wep: %d\n",
-		       wiphy_name(local->hw.wiphy), result);
-		goto fail_wep;
-	}
-
 	/* add one default STA interface if supported */
 	if (local->hw.wiphy->interface_modes & BIT(NL80211_IFTYPE_STATION)) {
 		result = ieee80211_if_add(local, "wlan%d", NULL,
@@ -967,13 +966,13 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 
 	return 0;
 
-fail_wep:
-	rate_control_deinitialize(local);
 fail_rate:
 	unregister_netdevice(local->mdev);
 	local->mdev = NULL;
 fail_dev:
 	rtnl_unlock();
+	ieee80211_wep_free(local);
+fail_wep:
 	sta_info_stop(local);
 fail_sta_info:
 	debugfs_hw_del(local);
-- 
1.5.4.3




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