2014-03-09 20:07:08

by Emil Goode

Subject: [PATCH 1/2] brcmsmac: fix deadlock on missing firmware

When brcm80211 firmware is not installed networking hangs.
A deadlock happens because we call ieee80211_unregister_hw()
from the .start callback of struct ieee80211_ops. When .start
is called we are under rtnl lock and ieee80211_unregister_hw()
tries to take it again.

Function call stack:

dev_change_flags()
__dev_change_flags()
__dev_open()
ASSERT_RTNL() <-- Assert rtnl lock
ops->ndo_open()

.ndo_open = ieee80211_open,

ieee80211_open()
ieee80211_do_open()
drv_start()
local->ops->start()

.start = brcms_ops_start,

brcms_ops_start()
brcms_remove()
ieee80211_unregister_hw()
rtnl_lock() <-- Here we deadlock

Introduced by:
commit 25b5632fb35ca61b8ae3eee235edcdc2883f7a5e
("brcmsmac: request firmware in .start() callback")

This patch fixes the bug by removing the call to brcms_remove()
and moves the brcms_request_fw() call to the top of the .start
callback to not initiate anything unless firmware is installed.

Signed-off-by: Emil Goode <[email protected]>
---
drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c b/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
index 925034b..93598cd 100644
--- a/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
+++ b/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
@@ -426,6 +426,12 @@ static int brcms_ops_start(struct ieee80211_hw *hw)
bool blocked;
int err;

+ if (!wl->ucode.bcm43xx_bomminor) {
+ err = brcms_request_fw(wl, wl->wlc->hw->d11core);
+ if (err)
+ return -ENOENT;
+ }
+
ieee80211_wake_queues(hw);
spin_lock_bh(&wl->lock);
blocked = brcms_rfkill_set_hw_state(wl);
@@ -433,14 +439,6 @@ static int brcms_ops_start(struct ieee80211_hw *hw)
if (!blocked)
wiphy_rfkill_stop_polling(wl->pub->ieee_hw->wiphy);

- if (!wl->ucode.bcm43xx_bomminor) {
- err = brcms_request_fw(wl, wl->wlc->hw->d11core);
- if (err) {
- brcms_remove(wl->wlc->hw->d11core);
- return -ENOENT;
- }
- }
-
spin_lock_bh(&wl->lock);
/* avoid acknowledging frames before a non-monitor device is added */
wl->mute_tx = true;
--
1.7.10.4

2014-03-09 20:07:09

by Emil Goode

Subject: [PATCH 2/2] brcmsmac: update comment to reflect the code

The brcms_attach function is defined as static but the comment is
saying that it should not be static or gcc will issue a warning.
I believe we can remove the comment as I don't se a problem with
this function being defined as static.

Signed-off-by: Emil Goode <[email protected]>
---
drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c | 6 ------
1 file changed, 6 deletions(-)

diff --git a/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c b/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
index 93598cd..8c5fa4e 100644
--- a/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
+++ b/drivers/net/wireless/brcm80211/brcmsmac/mac80211_if.c
@@ -1092,12 +1092,6 @@ static int ieee_hw_init(struct ieee80211_hw *hw)
* Attach to the WL device identified by vendor and device parameters.
* regs is a host accessible memory address pointing to WL device registers.
*
- * brcms_attach is not defined as static because in the case where no bus
- * is defined, wl_attach will never be called, and thus, gcc will issue
- * a warning that this function is defined but not used if we declare
- * it as static.
- *
- *
* is called in brcms_bcma_probe() context, therefore no locking required.
*/
static struct brcms_info *brcms_attach(struct bcma_device *pdev)
--
1.7.10.4