Sainath,
with rcu debugging and lock debugging I get the following splats.
I think doing a mutex_lock while in an rcu read-side is not allowed,
since mutex_lock can sleep.
This is in 4.11 and 4.12 and seems to be introduced with commit
d9f1f61c0801a7("tap: Extending tap device create/destroy APIs").
Christian
[ 125.678015] ===============================
[ 125.678018] [ ERR: suspicious RCU usage. ]
[ 125.678022] 4.11.0+ #18 Not tainted
[ 125.678025] -------------------------------
[ 125.678028] ./include/linux/rcupdate.h:521 Illegal context switch in RCU read-side critical section!
[ 125.678031]
other info that might help us debug this:
[ 125.678035]
rcu_scheduler_active = 2, debug_locks = 0
[ 125.678038] 2 locks held by libvirtd/3050:
[ 125.678041] #0: (rtnl_mutex){+.+.+.}, at: [<0000000000772b02>] rtnl_newlink+0x2ea/0x880
[ 125.678057] #1: (rcu_read_lock){......}, at: [<000003ff800dad00>] tap_get_minor+0x0/0x1d8 [tap]
[ 125.678068]
stack backtrace:
[ 125.678073] CPU: 26 PID: 3050 Comm: libvirtd Not tainted 4.11.0+ #18
[ 125.678076] Hardware name: IBM 2964 NC9 704 (LPAR)
[ 125.678079] Stack:
[ 125.678081] 000000fa977cb230 000000fa977cb2c0 0000000000000003 0000000000000000
[ 125.678091] 000000fa977cb360 000000fa977cb2d8 000000fa977cb2d8 0000000000000020
[ 125.678100] 0000000000000000 000003ff00000020 000000fa0000000a 000000fa0000000a
[ 125.678109] 000000000000000c 000000fa977cb328 0000000000000000 0000000000000000
[ 125.678119] 00000000008e2510 00000000001139ac 000000fa977cb2c0 000000fa977cb318
[ 125.678150] Call Trace:
[ 125.678157] ([<0000000000113872>] show_trace+0xea/0xf0)
[ 125.678160] [<0000000000113950>] show_stack+0x68/0xe0
[ 125.678165] [<000000000057ef8c>] dump_stack+0x94/0xd8
[ 125.678172] [<00000000001a4422>] ___might_sleep+0x21a/0x268
[ 125.678177] [<00000000008ca842>] __mutex_lock+0x52/0x968
[ 125.678180] [<00000000008cb192>] mutex_lock_nested+0x3a/0x48
[ 125.678184] [<000003ff800dadd6>] tap_get_minor+0xd6/0x1d8 [tap]
[ 125.678188] [<000003ff801773a2>] macvtap_device_event+0x9a/0x1a0 [macvtap]
[ 125.678191] [<000000000019bfbe>] notifier_call_chain+0x56/0x98
[ 125.678195] [<000000000019c1b2>] raw_notifier_call_chain+0x32/0x40
[ 125.678200] [<000000000075d014>] register_netdevice+0x3f4/0x508
[ 125.678204] [<000003ff801718a0>] macvlan_common_newlink+0x360/0x430 [macvlan]
[ 125.678207] [<000003ff80177564>] macvtap_newlink+0xbc/0xf0 [macvtap]
[ 125.678211] [<0000000000772e32>] rtnl_newlink+0x61a/0x880
[ 125.678214] [<000000000077313c>] rtnetlink_rcv_msg+0xa4/0x248
[ 125.678219] [<000000000079cec0>] netlink_rcv_skb+0xd8/0x108
[ 125.678222] [<000000000076f538>] rtnetlink_rcv+0x48/0x58
[ 125.678226] [<000000000079c750>] netlink_unicast+0x178/0x1f8
[ 125.678229] [<000000000079cbd4>] netlink_sendmsg+0x304/0x3b0
[ 125.678233] [<0000000000730676>] sock_sendmsg+0x6e/0x80
[ 125.678237] [<00000000007311b0>] ___sys_sendmsg+0x2a0/0x2a8
[ 125.678240] [<00000000007324d8>] __sys_sendmsg+0x60/0xa8
[ 125.678244] [<0000000000732ed4>] SyS_socketcall+0x33c/0x390
[ 125.678248] [<00000000008d08bc>] system_call+0xc4/0x258
[ 125.678251] INFO: lockdep is turned off.
[ 125.678255] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:747
[ 125.678257] in_atomic(): 1, irqs_disabled(): 0, pid: 3050, name: libvirtd
[ 125.678261] INFO: lockdep is turned off.
[ 125.678264] CPU: 26 PID: 3050 Comm: libvirtd Not tainted 4.11.0+ #18
[ 125.678267] Hardware name: IBM 2964 NC9 704 (LPAR)
[ 125.678269] Stack:
[ 125.678272] 000000fa977cb230 000000fa977cb2c0 0000000000000003 0000000000000000
[ 125.678281] 000000fa977cb360 000000fa977cb2d8 000000fa977cb2d8 0000000000000020
[ 125.678290] 0000000000000000 000000fa00000020 000000fa0000000a 000000fa0000000a
[ 125.678298] 000000000000000c 000000fa977cb328 0000000000000000 0000000000000000
[ 125.678308] 00000000008e2510 00000000001139ac 000000fa977cb2c0 000000fa977cb318
[ 125.678323] Call Trace:
[ 125.678326] ([<0000000000113872>] show_trace+0xea/0xf0)
[ 125.678330] [<0000000000113950>] show_stack+0x68/0xe0
[ 125.678334] [<000000000057ef8c>] dump_stack+0x94/0xd8
[ 125.678337] [<00000000001a438e>] ___might_sleep+0x186/0x268
[ 125.678341] [<00000000008ca842>] __mutex_lock+0x52/0x968
[ 125.678346] [<00000000008cb192>] mutex_lock_nested+0x3a/0x48
[ 125.678350] [<000003ff800dadd6>] tap_get_minor+0xd6/0x1d8 [tap]
[ 125.678354] [<000003ff801773a2>] macvtap_device_event+0x9a/0x1a0 [macvtap]
[ 125.678357] [<000000000019bfbe>] notifier_call_chain+0x56/0x98
[ 125.678360] [<000000000019c1b2>] raw_notifier_call_chain+0x32/0x40
[ 125.678364] [<000000000075d014>] register_netdevice+0x3f4/0x508
[ 125.678368] [<000003ff801718a0>] macvlan_common_newlink+0x360/0x430 [macvlan]
[ 125.678371] [<000003ff80177564>] macvtap_newlink+0xbc/0xf0 [macvtap]
[ 125.678374] [<0000000000772e32>] rtnl_newlink+0x61a/0x880
[ 125.678377] [<000000000077313c>] rtnetlink_rcv_msg+0xa4/0x248
[ 125.678380] [<000000000079cec0>] netlink_rcv_skb+0xd8/0x108
[ 125.678382] [<000000000076f538>] rtnetlink_rcv+0x48/0x58
[ 125.678386] [<000000000079c750>] netlink_unicast+0x178/0x1f8
[ 125.678389] [<000000000079cbd4>] netlink_sendmsg+0x304/0x3b0
[ 125.678392] [<0000000000730676>] sock_sendmsg+0x6e/0x80
[ 125.678395] [<00000000007311b0>] ___sys_sendmsg+0x2a0/0x2a8
[ 125.678398] [<00000000007324d8>] __sys_sendmsg+0x60/0xa8
[ 125.678401] [<0000000000732ed4>] SyS_socketcall+0x33c/0x390
[ 125.678404] [<00000000008d08bc>] system_call+0xc4/0x258
[ 125.678407] INFO: lockdep is turned off.
