| Message ID | 1335557509-32726-2-git-send-email-nhorman@tuxdriver.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Fri, 2012-04-27 at 16:11 -0400, Neil Horman wrote: > Eric Dumazet pointed out this warning in the drop_monitor protocol to me: > > 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@tuxdriver.com> > Reported-by: Eric Dumazet <eric.dumazet@gmail.com> > CC: David Miller <davem@davemloft.net> > --- Acked-by: Eric Dumazet <edumazet@google.com> Thanks Neil -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Apr 28, 2012 at 08:11:13AM +0200, Eric Dumazet wrote: > On Fri, 2012-04-27 at 16:11 -0400, Neil Horman wrote: > > Eric Dumazet pointed out this warning in the drop_monitor protocol to me: > > > > > 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@tuxdriver.com> > > Reported-by: Eric Dumazet <eric.dumazet@gmail.com> > > CC: David Miller <davem@davemloft.net> > > --- > > Acked-by: Eric Dumazet <edumazet@google.com> > > Thanks Neil > Anytmie, thanks for reporting it. Neil > > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c index 5c3c81a..a221a5b 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; @@ -214,7 +214,7 @@ 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); if (state == trace_state) { rc = -EAGAIN; @@ -253,7 +253,7 @@ static int set_all_monitor_traces(int state) rc = -EINPROGRESS; out_unlock: - spin_unlock(&trace_state_lock); + mutex_unlock(&trace_state_mutex); return rc; } @@ -296,12 +296,12 @@ 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; @@ -312,7 +312,7 @@ static int dropmon_net_event(struct notifier_block *ev_block, } } } - spin_unlock(&trace_state_lock); + mutex_unlock(&trace_state_mutex); break; } out:
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@tuxdriver.com> Reported-by: Eric Dumazet <eric.dumazet@gmail.com> CC: David Miller <davem@davemloft.net> --- net/core/drop_monitor.c | 14 +++++++------- 1 files changed, 7 insertions(+), 7 deletions(-)