On Mon, Aug 10, 2020 at 11:55:35AM +0200, Marco Elver wrote: > Unfortunately I get LOCKDEP_DEBUG warnings, when testing with one of > syzbot's configs. This appears at some point during boot (no other > test): > > DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled()) > WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:4875 > check_flags+0x52/0x200 kernel/locking/lockdep.c:4875 > Modules linked in: > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.8.0+ #8 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1 > 04/01/2014 > RIP: 0010:check_flags+0x52/0x200 kernel/locking/lockdep.c:4875 > Code: c0 74 48 e8 40 f7 a5 03 85 c0 74 20 83 3d bd 33 53 05 00 75 17 48 > c7 c7 ce 12 c9 85 48 c7 c6 04 8c ca 85 31 c0 e8 4e c1 f7 ff <0f> 0b 48 c7 c7 > db 8b ca 85 e9 8c 01 00 00 85 c0 75 0f 65 8b 05 c5 > RSP: 0000:ffffffff86203bf0 EFLAGS: 00010046 > RAX: 1f9fa70771052a00 RBX: 0000000000000000 RCX: ffffffff8627e980 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 > RBP: 0000000000000000 R08: ffffffff813d8494 R09: 0000000000000000 > R10: 0000000000000012 R11: ffffffff8627e980 R12: ffffffff8627e980 > R13: ffffffff862e3420 R14: 00000000ffffffff R15: 0000000000000046 > FS: 0000000000000000(0000) GS:ffff88881fa00000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: ffff88883ffff000 CR3: 0000000006275001 CR4: 0000000000770ef0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 00000000 > Call Trace: > lock_is_held_type+0x4d/0x110 kernel/locking/lockdep.c:5043 > lock_is_held include/linux/lockdep.h:266 [inline] > rcu_read_lock_sched_held+0x41/0x90 kernel/rcu/update.c:136 > trace_lock_acquire+0x49/0x120 include/trace/events/lock.h:13 > lock_acquire+0x8d/0x2c0 kernel/locking/lockdep.c:5003 > mutex_trylock+0xdd/0x120 kernel/locking/mutex.c:1420
*groan*, indeed! Which is the direct result of lockdep recursion because we pulled that tracepoint out from under the recursion thing. Let me go prod this with a sharp stick...
