rt2x00: use atomic variable for seqno

commit e5851dac2c95af7159716832300b9f50c62c648e upstream.

Remove spinlock as atomic_t can be used instead. Note we use only 16
lower bits, upper bits are changed but we impilcilty cast to u16.

This fix possible deadlock on IBSS mode reproted by lockdep:

=================================
[ INFO: inconsistent lock state ]
3.4.0-wl+ #4 Not tainted
---------------------------------
inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
kworker/u:2/30374 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (&(&intf->seqlock)->rlock){+.?...}, at: [<f9979a20>] rt2x00queue_create_tx_descriptor+0x380/0x490 [rt2x00lib]
{IN-SOFTIRQ-W} state was registered at:
  [<c04978ab>] __lock_acquire+0x47b/0x1050
  [<c0498504>] lock_acquire+0x84/0xf0
  [<c0835733>] _raw_spin_lock+0x33/0x40
  [<f9979a20>] rt2x00queue_create_tx_descriptor+0x380/0x490 [rt2x00lib]
  [<f9979f2a>] rt2x00queue_write_tx_frame+0x1a/0x300 [rt2x00lib]
  [<f997834f>] rt2x00mac_tx+0x7f/0x380 [rt2x00lib]
  [<f98fe363>] __ieee80211_tx+0x1b3/0x300 [mac80211]
  [<f98ffdf5>] ieee80211_tx+0x105/0x130 [mac80211]
  [<f99000dd>] ieee80211_xmit+0xad/0x100 [mac80211]
  [<f9900519>] ieee80211_subif_start_xmit+0x2d9/0x930 [mac80211]
  [<c0782e87>] dev_hard_start_xmit+0x307/0x660
  [<c079bb71>] sch_direct_xmit+0xa1/0x1e0
  [<c0784bb3>] dev_queue_xmit+0x183/0x730
  [<c078c27a>] neigh_resolve_output+0xfa/0x1e0
  [<c07b436a>] ip_finish_output+0x24a/0x460
  [<c07b4897>] ip_output+0xb7/0x100
  [<c07b2d60>] ip_local_out+0x20/0x60
  [<c07e01ff>] igmpv3_sendpack+0x4f/0x60
  [<c07e108f>] igmp_ifc_timer_expire+0x29f/0x330
  [<c04520fc>] run_timer_softirq+0x15c/0x2f0
  [<c0449e3e>] __do_softirq+0xae/0x1e0
irq event stamp: 18380437
hardirqs last  enabled at (18380437): [<c0526027>] __slab_alloc.clone.3+0x67/0x5f0
hardirqs last disabled at (18380436): [<c0525ff3>] __slab_alloc.clone.3+0x33/0x5f0
softirqs last  enabled at (18377616): [<c0449eb3>] __do_softirq+0x123/0x1e0
softirqs last disabled at (18377611): [<c041278d>] do_softirq+0x9d/0xe0

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&(&intf->seqlock)->rlock);
  <Interrupt>
    lock(&(&intf->seqlock)->rlock);

 *** DEADLOCK ***

4 locks held by kworker/u:2/30374:
 #0:  (wiphy_name(local->hw.wiphy)){++++.+}, at: [<c045cf99>] process_one_work+0x109/0x3f0
 #1:  ((&sdata->work)){+.+.+.}, at: [<c045cf99>] process_one_work+0x109/0x3f0
 #2:  (&ifibss->mtx){+.+.+.}, at: [<f98f005b>] ieee80211_ibss_work+0x1b/0x470 [mac80211]
 #3:  (&intf->beacon_skb_mutex){+.+...}, at: [<f997a644>] rt2x00queue_update_beacon+0x24/0x50 [rt2x00lib]

stack backtrace:
Pid: 30374, comm: kworker/u:2 Not tainted 3.4.0-wl+ #4
Call Trace:
 [<c04962a6>] print_usage_bug+0x1f6/0x220
 [<c0496a12>] mark_lock+0x2c2/0x300
 [<c0495ff0>] ? check_usage_forwards+0xc0/0xc0
 [<c04978ec>] __lock_acquire+0x4bc/0x1050
 [<c0527890>] ? __kmalloc_track_caller+0x1c0/0x1d0
 [<c0777fb6>] ? copy_skb_header+0x26/0x90
 [<c0498504>] lock_acquire+0x84/0xf0
 [<f9979a20>] ? rt2x00queue_create_tx_descriptor+0x380/0x490 [rt2x00lib]
 [<c0835733>] _raw_spin_lock+0x33/0x40
 [<f9979a20>] ? rt2x00queue_create_tx_descriptor+0x380/0x490 [rt2x00lib]
 [<f9979a20>] rt2x00queue_create_tx_descriptor+0x380/0x490 [rt2x00lib]
 [<f997a5cf>] rt2x00queue_update_beacon_locked+0x5f/0xb0 [rt2x00lib]
 [<f997a64d>] rt2x00queue_update_beacon+0x2d/0x50 [rt2x00lib]
 [<f9977e3a>] rt2x00mac_bss_info_changed+0x1ca/0x200 [rt2x00lib]
 [<f9977c70>] ? rt2x00mac_remove_interface+0x70/0x70 [rt2x00lib]
 [<f98e4dd0>] ieee80211_bss_info_change_notify+0xe0/0x1d0 [mac80211]
 [<f98ef7b8>] __ieee80211_sta_join_ibss+0x3b8/0x610 [mac80211]
 [<c0496ab4>] ? mark_held_locks+0x64/0xc0
 [<c0440012>] ? virt_efi_query_capsule_caps+0x12/0x50
 [<f98efb09>] ieee80211_sta_join_ibss+0xf9/0x140 [mac80211]
 [<f98f0456>] ieee80211_ibss_work+0x416/0x470 [mac80211]
 [<c0496d8b>] ? trace_hardirqs_on+0xb/0x10
 [<c077683b>] ? skb_dequeue+0x4b/0x70
 [<f98f207f>] ieee80211_iface_work+0x13f/0x230 [mac80211]
 [<c045cf99>] ? process_one_work+0x109/0x3f0
 [<c045d015>] process_one_work+0x185/0x3f0
 [<c045cf99>] ? process_one_work+0x109/0x3f0
 [<f98f1f40>] ? ieee80211_teardown_sdata+0xa0/0xa0 [mac80211]
 [<c045ed86>] worker_thread+0x116/0x270
 [<c045ec70>] ? manage_workers+0x1e0/0x1e0
 [<c0462f64>] kthread+0x84/0x90
 [<c0462ee0>] ? __init_kthread_worker+0x60/0x60
 [<c083d382>] kernel_thread_helper+0x6/0x10

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Helmut Schaa <helmut.schaa@googlemail.com>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/wireless/rt2x00/rt2x00.h b/drivers/net/wireless/rt2x00/rt2x00.h
index 471f87cab4abe53650de055058d3c9d61a2a2ecc..c264dfa6e61189562f020052649ace8ebdfe9509 100644 (file)
--- a/drivers/net/wireless/rt2x00/rt2x00.h
+++ b/drivers/net/wireless/rt2x00/rt2x00.h
@@ -396,8 +396,7 @@ struct rt2x00_intf {
         * for hardware which doesn't support hardware
         * sequence counting.
         */
-       spinlock_t seqlock;
-       u16 seqno;
+       atomic_t seqno;
 };
 
 static inline struct rt2x00_intf* vif_to_intf(struct ieee80211_vif *vif)

diff --git a/drivers/net/wireless/rt2x00/rt2x00mac.c b/drivers/net/wireless/rt2x00/rt2x00mac.c
index 2df2eb6d3e06bf892d7a52eb9cbd1dd13f5e7c95..a8885f0600609e7350f47d6cce717eccf7fcd2b8 100644 (file)
--- a/drivers/net/wireless/rt2x00/rt2x00mac.c
+++ b/drivers/net/wireless/rt2x00/rt2x00mac.c
@@ -277,7 +277,6 @@ int rt2x00mac_add_interface(struct ieee80211_hw *hw,
        else
                rt2x00dev->intf_sta_count++;
 
-       spin_lock_init(&intf->seqlock);
        mutex_init(&intf->beacon_skb_mutex);
        intf->beacon = entry;
 

diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
index 9b1b2b7a7807226717a6a1b463cdf9fdc7a70f2e..50f92d5a2bdc282276a5d040f6d7573aec601bf3 100644 (file)
--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -207,6 +207,7 @@ static void rt2x00queue_create_tx_descriptor_seq(struct rt2x00_dev *rt2x00dev,
        struct ieee80211_tx_info *tx_info = IEEE80211_SKB_CB(skb);
        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
        struct rt2x00_intf *intf = vif_to_intf(tx_info->control.vif);
+       u16 seqno;
 
        if (!(tx_info->flags & IEEE80211_TX_CTL_ASSIGN_SEQ))
                return;
@@ -227,15 +228,13 @@ static void rt2x00queue_create_tx_descriptor_seq(struct rt2x00_dev *rt2x00dev,
         * sequence counting per-frame, since those will override the
         * sequence counter given by mac80211.
         */
-       spin_lock(&intf->seqlock);
-
        if (test_bit(ENTRY_TXD_FIRST_FRAGMENT, &txdesc->flags))
-               intf->seqno += 0x10;
-       hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
-       hdr->seq_ctrl |= cpu_to_le16(intf->seqno);
-
-       spin_unlock(&intf->seqlock);
+               seqno = atomic_add_return(0x10, &intf->seqno);
+       else
+               seqno = atomic_read(&intf->seqno);
 
+       hdr->seq_ctrl &= cpu_to_le16(IEEE80211_SCTL_FRAG);
+       hdr->seq_ctrl |= cpu_to_le16(seqno);
 }
 
 static void rt2x00queue_create_tx_descriptor_plcp(struct rt2x00_dev *rt2x00dev,