From: Neil Horman <nhorman@xxxxxxxxxxxxx>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit cde2e9a651b76d8db36ae94cd0febc82b637e5dd upstream.
Eric Dumazet pointed out this warning in the drop_monitor protocol to me:
[ 38.352571] BUG: sleeping function called from invalid context at kernel/mutex.c:85
[ 38.352576] in_atomic(): 1, irqs_disabled(): 0, pid: 4415, name: dropwatch
[ 38.352580] Pid: 4415, comm: dropwatch Not tainted 3.4.0-rc2+ #71
[ 38.352582] Call Trace:
[ 38.352592] [<ffffffff8153aaf0>] ? trace_napi_poll_hit+0xd0/0xd0
[ 38.352599] [<ffffffff81063f2a>] __might_sleep+0xca/0xf0
[ 38.352606] [<ffffffff81655b16>] mutex_lock+0x26/0x50
[ 38.352610] [<ffffffff8153aaf0>] ? trace_napi_poll_hit+0xd0/0xd0
[ 38.352616] [<ffffffff810b72d9>] tracepoint_probe_register+0x29/0x90
[ 38.352621] [<ffffffff8153a585>] set_all_monitor_traces+0x105/0x170
[ 38.352625] [<ffffffff8153a8ca>] net_dm_cmd_trace+0x2a/0x40
[ 38.352630] [<ffffffff8154a81a>] genl_rcv_msg+0x21a/0x2b0
[ 38.352636] [<ffffffff810f8029>] ? zone_statistics+0x99/0xc0
[ 38.352640] [<ffffffff8154a600>] ? genl_rcv+0x30/0x30
[ 38.352645] [<ffffffff8154a059>] netlink_rcv_skb+0xa9/0xd0
[ 38.352649] [<ffffffff8154a5f0>] genl_rcv+0x20/0x30
[ 38.352653] [<ffffffff81549a7e>] netlink_unicast+0x1ae/0x1f0
[ 38.352658] [<ffffffff81549d76>] netlink_sendmsg+0x2b6/0x310
[ 38.352663] [<ffffffff8150824f>] sock_sendmsg+0x10f/0x130
[ 38.352668] [<ffffffff8150abe0>] ? move_addr_to_kernel+0x60/0xb0
[ 38.352673] [<ffffffff81515f04>] ? verify_iovec+0x64/0xe0
[ 38.352677] [<ffffffff81509c46>] __sys_sendmsg+0x386/0x390
[ 38.352682] [<ffffffff810ffaf9>] ? handle_mm_fault+0x139/0x210
[ 38.352687] [<ffffffff8165b5bc>] ? do_page_fault+0x1ec/0x4f0
[ 38.352693] [<ffffffff8106ba4d>] ? set_next_entity+0x9d/0xb0
[ 38.352699] [<ffffffff81310b49>] ? tty_ldisc_deref+0x9/0x10
[ 38.352703] [<ffffffff8106d363>] ? pick_next_task_fair+0x63/0x140
[ 38.352708] [<ffffffff8150b8d4>] sys_sendmsg+0x44/0x80
[ 38.352713] [<ffffffff8165f8e2>] system_call_fastpath+0x16/0x1b
It stems from holding a spinlock (trace_state_lock) while attempting to register
or unregister tracepoint hooks, making in_atomic() true in this context, leading
to the warning when the tracepoint calls might_sleep() while its taking a mutex.
Since we only use the trace_state_lock to prevent trace protocol state races, as
well as hardware stat list updates on an rcu write side, we can just convert the
spinlock to a mutex to avoid this problem.
Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Reported-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
CC: David Miller <davem@xxxxxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
net/core/drop_monitor.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index cf208d8042b1..e596db9fefd0 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -42,7 +42,7 @@ static void send_dm_alert(struct work_struct *unused);
* netlink alerts
*/
static int trace_state = TRACE_OFF;
-static DEFINE_SPINLOCK(trace_state_lock);
+static DEFINE_MUTEX(trace_state_mutex);
struct per_cpu_dm_data {
struct work_struct dm_alert_work;
@@ -221,7 +221,7 @@ static int set_all_monitor_traces(int state)
struct dm_hw_stat_delta *new_stat = NULL;
struct dm_hw_stat_delta *temp;
- spin_lock(&trace_state_lock);
+ mutex_lock(&trace_state_mutex);
switch (state) {
case TRACE_ON:
@@ -252,7 +252,7 @@ static int set_all_monitor_traces(int state)
if (!rc)
trace_state = state;
- spin_unlock(&trace_state_lock);
+ mutex_unlock(&trace_state_mutex);
if (rc)
return -EINPROGRESS;
@@ -297,12 +297,12 @@ static int dropmon_net_event(struct notifier_block *ev_block,
new_stat->dev = dev;
new_stat->last_rx = jiffies;
- spin_lock(&trace_state_lock);
+ mutex_lock(&trace_state_mutex);
list_add_rcu(&new_stat->list, &hw_stats_list);
- spin_unlock(&trace_state_lock);
+ mutex_unlock(&trace_state_mutex);
break;
case NETDEV_UNREGISTER:
- spin_lock(&trace_state_lock);
+ mutex_lock(&trace_state_mutex);
list_for_each_entry_safe(new_stat, tmp, &hw_stats_list, list) {
if (new_stat->dev == dev) {
new_stat->dev = NULL;
@@ -313,7 +313,7 @@ static int dropmon_net_event(struct notifier_block *ev_block,
}
}
}
- spin_unlock(&trace_state_lock);
+ mutex_unlock(&trace_state_mutex);
break;
}
out:
--
1.8.5.2
--
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