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Message-ID: <1335466889.2775.60.camel@edumazet-glaptop> Date: Thu, 26 Apr 2012 21:01:29 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: Neil Horman <nhorman@...driver.com> Cc: netdev@...r.kernel.org, David Miller <davem@...emloft.net> Subject: Re: [PATCH 1/2] drop_monitor: fix sleeping in invalid context warning On Thu, 2012-04-26 at 14:47 -0400, Neil Horman wrote: > 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@...driver.com> > Reported-by: Eric Dumazet <eric.dumazet@...il.com> > CC: David Miller <davem@...emloft.net> > --- > net/core/drop_monitor.c | 14 +++++++------- > 1 files changed, 7 insertions(+), 7 deletions(-) > > diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c > index 5c3c81a..04ce1dd 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_lock); Maybe rename it to trace_state_mutex ? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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