bisecting fixing commit since 7ae77150d94d3b535c7b85e6b3647113095e79bf building syzkaller on 54566aff1679fc74487d3efb9f7bbfbc21beed4b testing commit 7ae77150d94d3b535c7b85e6b3647113095e79bf with gcc (GCC) 8.1.0 kernel signature: b30a3eabf45287ebf196ad7ed140bdc895ba43d7e78c2a500f237a9c1e9bb163 all runs: crashed: WARNING: suspicious RCU usage in ctrl_cmd_new_lookup testing current HEAD 15bc20c6af4ceee97a1f90b43c0e386643c071b4 testing commit 15bc20c6af4ceee97a1f90b43c0e386643c071b4 with gcc (GCC) 8.1.0 kernel signature: b28029ef4a01394c011459dff794bdec0ab287992ef9ea987f9bfd85255cde08 all runs: crashed: WARNING: suspicious RCU usage in ctrl_cmd_new_lookup revisions tested: 2, total time: 17m21.213225343s (build: 10m25.860055191s, test: 6m21.919499798s) the crash still happens on HEAD commit msg: Merge tag 'tty-5.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty crash: WARNING: suspicious RCU usage in ctrl_cmd_new_lookup ============================= WARNING: suspicious RCU usage 5.9.0-rc2-syzkaller #0 Not tainted ----------------------------- include/linux/radix-tree.h:176 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by kworker/u4:3/296: #0: ffff88812b04f138 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff88812b04f138 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff88812b04f138 ((wq_completion)qrtr_ns_handler){+.+.}-{0:0}, at: process_one_work+0x1de/0x5f0 kernel/workqueue.c:2240 #1: ffffc90000e0fe70 ((work_completion)(&qrtr_ns.work)){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #1: ffffc90000e0fe70 ((work_completion)(&qrtr_ns.work)){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #1: ffffc90000e0fe70 ((work_completion)(&qrtr_ns.work)){+.+.}-{0:0}, at: process_one_work+0x1de/0x5f0 kernel/workqueue.c:2240 stack backtrace: CPU: 0 PID: 296 Comm: kworker/u4:3 Not tainted 5.9.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: qrtr_ns_handler qrtr_ns_worker Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xb3/0xec lib/dump_stack.c:118 radix_tree_deref_slot include/linux/radix-tree.h:176 [inline] ctrl_cmd_new_lookup+0x284/0x2b0 net/qrtr/ns.c:558 qrtr_ns_worker+0x11a/0x717 net/qrtr/ns.c:674 process_one_work+0x26a/0x5f0 kernel/workqueue.c:2269 worker_thread+0x38/0x380 kernel/workqueue.c:2415 kthread+0x148/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 failed to send lookup notification failed to send lookup notification failed to send lookup notification failed to send lookup notification failed to send lookup notification failed to send lookup notification failed to send lookup notification failed to send lookup notification failed to send lookup 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