=============================
WARNING: suspicious RCU usage
4.15.0+ #308 Not tainted
-----------------------------
./include/linux/rcupdate.h:302 Illegal context switch in RCU read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor4/7631:
 #0:  (rcu_read_lock){....}, at: [<000000002a123e63>] __rds_conn_create+0xe46/0x1b50 net/rds/connection.c:218

stack backtrace:
CPU: 0 PID: 7631 Comm: syz-executor4 Not tainted 4.15.0+ #308
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4592
 rcu_preempt_sleep_check include/linux/rcupdate.h:301 [inline]
 ___might_sleep+0x385/0x470 kernel/sched/core.c:6093
 __might_sleep+0x95/0x190 kernel/sched/core.c:6081
 slab_pre_alloc_hook mm/slab.h:420 [inline]
 slab_alloc mm/slab.c:3365 [inline]
 kmem_cache_alloc+0x2a2/0x760 mm/slab.c:3539
 rds_tcp_conn_alloc+0xa7/0x4e0 net/rds/tcp.c:296
 __rds_conn_create+0x112f/0x1b50 net/rds/connection.c:227
 rds_conn_create_outgoing+0x3f/0x50 net/rds/connection.c:309
 rds_sendmsg+0xda3/0x2390 net/rds/send.c:1126
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2046
 __sys_sendmsg+0xe5/0x210 net/socket.c:2080
 SYSC_sendmsg net/socket.c:2091 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2087
 do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x453a59
RSP: 002b:00007f46aa874c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f46aa8756d4 RCX: 0000000000453a59
RDX: 0000000000000000 RSI: 0000000020006fc8 RDI: 0000000000000013
RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004b5 R14: 00000000006f7198 R15: 0000000000000000
BUG: sleeping function called from invalid context at mm/slab.h:420
in_atomic(): 1, irqs_disabled(): 0, pid: 7631, name: syz-executor4
atomic_op 00000000e5efda93 conn xmit_atomic           (null)
1 lock held by syz-executor4/7631:
 #0:  (rcu_read_lock){....}, at: [<000000002a123e63>] __rds_conn_create+0xe46/0x1b50 net/rds/connection.c:218
CPU: 0 PID: 7631 Comm: syz-executor4 Not tainted 4.15.0+ #308
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 ___might_sleep+0x2b2/0x470 kernel/sched/core.c:6128
 __might_sleep+0x95/0x190 kernel/sched/core.c:6081
 slab_pre_alloc_hook mm/slab.h:420 [inline]
 slab_alloc mm/slab.c:3365 [inline]
 kmem_cache_alloc+0x2a2/0x760 mm/slab.c:3539
 rds_tcp_conn_alloc+0xa7/0x4e0 net/rds/tcp.c:296
 __rds_conn_create+0x112f/0x1b50 net/rds/connection.c:227
 rds_conn_create_outgoing+0x3f/0x50 net/rds/connection.c:309
 rds_sendmsg+0xda3/0x2390 net/rds/send.c:1126
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 ___sys_sendmsg+0x767/0x8b0 net/socket.c:2046
 __sys_sendmsg+0xe5/0x210 net/socket.c:2080
 SYSC_sendmsg net/socket.c:2091 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2087
 do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x453a59
RSP: 002b:00007f46aa874c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f46aa8756d4 RCX: 0000000000453a59
RDX: 0000000000000000 RSI: 0000000020006fc8 RDI: 0000000000000013
RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000000004b5 R14: 00000000006f7198 R15: 0000000000000000
------------[ cut here ]------------
IRQs not enabled as expected
WARNING: CPU: 0 PID: 7631 at kernel/softirq.c:162 __local_bh_enable_ip+0x1bb/0x230 kernel/softirq.c:162