[PATCH 3.14 164/228] iwlwifi: mvm: fix setting channel in monitor mode

Greg Kroah-Hartman
2014-06-05T00:10:23Z

From: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

commit 1c4abec0baf25ffb92a28cc99d4231feeaa4d3f3 upstream.

There was a deadlock in monitor mode when we were setting the
channel if the channel was not 1.

======================================================
[ INFO: possible circular locking dependency detected ]
3.14.3 #4 Not tainted
-------------------------------------------------------
iw/3323 is trying to acquire lock:
(&local->chanctx_mtx){+.+.+.}, at: [<ffffffffa062e2f2>] ieee80211_vif_release_channel+0x42/0xb0 [mac80211]

but task is already holding lock:
(&local->iflist_mtx){+.+...}, at: [<ffffffffa0609e0a>] ieee80211_set_monitor_channel+0x5a/0x1b0 [mac80211]

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&local->iflist_mtx){+.+...}:
[<ffffffff810d95bb>] __lock_acquire+0xb3b/0x13b0
[<ffffffff810d9ee0>] lock_acquire+0xb0/0x1f0
[<ffffffff817eb9c8>] mutex_lock_nested+0x78/0x4f0
[<ffffffffa06225cf>] ieee80211_iterate_active_interfaces+0x2f/0x60 [mac80211]
[<ffffffffa0518189>] iwl_mvm_recalc_multicast+0x49/0xa0 [iwlmvm]
[<ffffffffa051822e>] iwl_mvm_configure_filter+0x4e/0x70 [iwlmvm]
[<ffffffffa05e6d43>] ieee80211_configure_filter+0x153/0x5f0 [mac80211]
[<ffffffffa05e71f5>] ieee80211_reconfig_filter+0x15/0x20 [mac80211]
[snip]

-> #1 (&mvm->mutex){+.+.+.}:
[<ffffffff810d95bb>] __lock_acquire+0xb3b/0x13b0
[<ffffffff810d9ee0>] lock_acquire+0xb0/0x1f0
[<ffffffff817eb9c8>] mutex_lock_nested+0x78/0x4f0
[<ffffffffa0517246>] iwl_mvm_add_chanctx+0x56/0xe0 [iwlmvm]
[<ffffffffa062ca1e>] ieee80211_new_chanctx+0x13e/0x410 [mac80211]
[<ffffffffa062d953>] ieee80211_vif_use_channel+0x1c3/0x5a0 [mac80211]
[<ffffffffa06035ab>] ieee80211_add_virtual_monitor+0x1ab/0x6b0 [mac80211]
[<ffffffffa06052ea>] ieee80211_do_open+0xe6a/0x15a0 [mac80211]
[<ffffffffa0605a79>] ieee80211_open+0x59/0x60 [mac80211]
[snip]

-> #0 (&local->chanctx_mtx){+.+.+.}:
[<ffffffff810d6cb7>] check_prevs_add+0x977/0x980
[<ffffffff810d95bb>] __lock_acquire+0xb3b/0x13b0
[<ffffffff810d9ee0>] lock_acquire+0xb0/0x1f0
[<ffffffff817eb9c8>] mutex_lock_nested+0x78/0x4f0
[<ffffffffa062e2f2>] ieee80211_vif_release_channel+0x42/0xb0 [mac80211]
[<ffffffffa0609ec3>] ieee80211_set_monitor_channel+0x113/0x1b0 [mac80211]
[<ffffffffa058fb37>] cfg80211_set_monitor_channel+0x77/0x2b0 [cfg80211]
[<ffffffffa056e0b2>] __nl80211_set_channel+0x122/0x140 [cfg80211]
[<ffffffffa0581374>] nl80211_set_wiphy+0x284/0xaf0 [cfg80211]
[snip]

other info that might help us debug this:

Chain exists of:
&local->chanctx_mtx --> &mvm->mutex --> &local->iflist_mtx

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&local->iflist_mtx);
lock(&mvm->mutex);
lock(&local->iflist_mtx);
lock(&local->chanctx_mtx);

*** DEADLOCK ***

This deadlock actually occurs:
INFO: task iw:3323 blocked for more than 120 seconds.
Not tainted 3.14.3 #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
iw D ffff8800c8afcd80 4192 3323 3322 0x00000000
ffff880078fdb7e0 0000000000000046 ffff8800c8afcd80 ffff880078fdbfd8
00000000001d5540 00000000001d5540 ffff8801141b0000 ffff8800c8afcd80
ffff880078ff9e38 ffff880078ff9e38 ffff880078ff9e40 0000000000000246
Call Trace:
[<ffffffff817ea841>] schedule_preempt_disabled+0x31/0x80
[<ffffffff817ebaed>] mutex_lock_nested+0x19d/0x4f0
[<ffffffffa06225cf>] ? ieee80211_iterate_active_interfaces+0x2f/0x60 [mac80211]
[<ffffffffa06225cf>] ? ieee80211_iterate_active_interfaces+0x2f/0x60 [mac80211]
[<ffffffffa052a680>] ? iwl_mvm_power_mac_update_mode+0xc0/0xc0 [iwlmvm]
[<ffffffffa06225cf>] ieee80211_iterate_active_interfaces+0x2f/0x60 [mac80211]
[<ffffffffa0529357>] _iwl_mvm_power_update_binding+0x27/0x80 [iwlmvm]
[<ffffffffa0516eb1>] iwl_mvm_unassign_vif_chanctx+0x81/0xc0 [iwlmvm]
[<ffffffffa062d3ff>] __ieee80211_vif_release_channel+0xdf/0x470 [mac80211]
[<ffffffffa062e2fa>] ieee80211_vif_release_channel+0x4a/0xb0 [mac80211]
[<ffffffffa0609ec3>] ieee80211_set_monitor_channel+0x113/0x1b0 [mac80211]
[<ffffffffa058fb37>] cfg80211_set_monitor_channel+0x77/0x2b0 [cfg80211]
[<ffffffffa056e0b2>] __nl80211_set_channel+0x122/0x140 [cfg80211]
[<ffffffffa0581374>] nl80211_set_wiphy+0x284/0xaf0 [cfg80211]

This fixes https://bugzilla.kernel.org/show_bug.cgi?id=75541

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/wireless/iwlwifi/mvm/mac80211.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/wireless/iwlwifi/mvm/mac80211.c
+++ b/drivers/net/wireless/iwlwifi/mvm/mac80211.c
@@ -796,7 +796,7 @@ static void iwl_mvm_mc_iface_iterator(vo
memcpy(cmd->bssid, vif->bss_conf.bssid, ETH_ALEN);
len = roundup(sizeof(*cmd) + cmd->count * ETH_ALEN, 4);

- ret = iwl_mvm_send_cmd_pdu(mvm, MCAST_FILTER_CMD, CMD_SYNC, len, cmd);
+ ret = iwl_mvm_send_cmd_pdu(mvm, MCAST_FILTER_CMD, CMD_ASYNC, len, cmd);
if (ret)
IWL_ERR(mvm, "mcast filter cmd error. ret=%d\n", ret);
}
@@ -812,7 +812,7 @@ static void iwl_mvm_recalc_multicast(str
if (WARN_ON_ONCE(!mvm->mcast_filter_cmd))
return;

- ieee80211_iterate_active_interfaces(
+ ieee80211_iterate_active_interfaces_atomic(
mvm->hw, IEEE80211_IFACE_ITER_NORMAL,
iwl_mvm_mc_iface_iterator, &iter_data);
}