FYI, we noticed the below changes on
https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git for-kbuild-bot/current-stable
commit 63a745aa6ac924a1dd17567e03bac83050afc8de ("ptrace: fix ptrace vs tasklist_lock race")
+-------------------------------------------------+------------+------------+
| | 722e07cda3 | 63a745aa6a |
+-------------------------------------------------+------------+------------+
| boot_successes | 52 | 27 |
| boot_failures | 0 | 6 |
| inconsistent{HARDIRQ-ON-W}->{IN-HARDIRQ-W}usage | 0 | 6 |
| backtrace:ptrace_check_attach | 0 | 6 |
| backtrace:SyS_ptrace | 0 | 6 |
| backtrace:cpu_startup_entry | 0 | 2 |
+-------------------------------------------------+------------+------------+
[ 29.600508] [ INFO: inconsistent lock state ]
[ 29.601341] 4.4.0-rc6-00128-g63a745a #1 Not tainted
[ 29.602035] ---------------------------------
[ 29.602667] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
[ 29.603480] swapper/1/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
[ 29.604191] (&(&sighand->siglock)->rlock){?.+...}, at: [<ffffffff810e4d01>] __lock_task_sighand+0xb5/0x10a
[ 29.605813] {HARDIRQ-ON-W} state was registered at:
[ 29.606553] [<ffffffff811151e6>] mark_held_locks+0x5e/0x74
[ 29.607395] [<ffffffff81115340>] trace_hardirqs_on_caller+0x144/0x197
[ 29.608327] [<ffffffff811153a0>] trace_hardirqs_on+0xd/0xf
[ 29.609215] [<ffffffff82e30b3b>] _raw_spin_unlock_irq+0x2c/0x3b
[ 29.610149] [<ffffffff810e0fdb>] ptrace_check_attach+0xbc/0x147
[ 29.611038] [<ffffffff810e19a2>] SyS_ptrace+0x97/0xea
[ 29.611827] [<ffffffff82e314b2>] entry_SYSCALL_64_fastpath+0x12/0x76
[ 29.612807] irq event stamp: 160226
[ 29.613540] hardirqs last enabled at (160223): [<ffffffff8105f2e9>] default_idle+0x1f/0x37
[ 29.614821] hardirqs last disabled at (160224): [<ffffffff82e32267>] apic_timer_interrupt+0x87/0xa0
[ 29.616140] softirqs last enabled at (160226): [<ffffffff810dc633>] _local_bh_enable+0x42/0x44
[ 29.617461] softirqs last disabled at (160225): [<ffffffff810dd405>] irq_enter+0x2e/0x65
[ 29.618704]
[ 29.618704] other info that might help us debug this:
[ 29.619679] Possible unsafe locking scenario:
[ 29.619679]
[ 29.620598] CPU0
[ 29.621064] ----
[ 29.621482] lock(&(&sighand->siglock)->rlock);
[ 29.622311] <Interrupt>
[ 29.622747] lock(&(&sighand->siglock)->rlock);
[ 29.623562]
[ 29.623562] *** DEADLOCK ***
[ 29.623562]
[ 29.624603] 2 locks held by swapper/1/0:
[ 29.625274] #0: (rcu_read_lock){......}, at: [<ffffffff810e2df2>] rcu_read_lock+0x0/0x68
[ 29.626808] #1: (rcu_read_lock){......}, at: [<ffffffff810e2df2>] rcu_read_lock+0x0/0x68
[ 29.628333]
[ 29.628333] stack backtrace:
[ 29.629258] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.0-rc6-00128-g63a745a #1
[ 29.630352] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[ 29.631563] 0000000000000000 ffff880034803c00 ffffffff8173e2ff ffff8800329d82c0
[ 29.632992] ffff880034803c50 ffffffff81114f72 0000000000000000 0000000000000000
[ 29.635104] 0000000000000001 0000000000000000 ffff8800329d8b60 ffffffff81114825
[ 29.637195] Call Trace:
[ 29.637910] <IRQ> [<ffffffff8173e2ff>] dump_stack+0x4b/0x63
[ 29.639263] [<ffffffff81114f72>] print_usage_bug+0x1ba/0x1cf
[ 29.640430] [<ffffffff81114825>] ? check_usage_backwards+0xba/0xba
[ 29.641721] [<ffffffff8111509a>] mark_lock+0x113/0x201
[ 29.642945] [<ffffffff8111598d>] __lock_acquire+0x343/0xdee
[ 29.644210] [<ffffffff810e4d01>] ? __lock_task_sighand+0xb5/0x10a
[ 29.645453] [<ffffffff81115a59>] ? __lock_acquire+0x40f/0xdee
[ 29.646649] [<ffffffff811167ce>] lock_acquire+0x10a/0x196
[ 29.647773] [<ffffffff811167ce>] ? lock_acquire+0x10a/0x196
[ 29.648952] [<ffffffff810e4d01>] ? __lock_task_sighand+0xb5/0x10a
[ 29.650180] [<ffffffff82e307d4>] _raw_spin_lock+0x34/0x6a
[ 29.651391] [<ffffffff810e4d01>] ? __lock_task_sighand+0xb5/0x10a
[ 29.652741] [<ffffffff810e4d01>] __lock_task_sighand+0xb5/0x10a
[ 29.654091] [<ffffffff810e4d88>] do_send_sig_info+0x32/0x72
[ 29.655338] [<ffffffff810e521a>] group_send_sig_info+0x4e/0x56
[ 29.656533] [<ffffffff810e5352>] kill_pid_info+0x44/0x63
[ 29.657621] [<ffffffff8113ad9b>] it_real_fn+0xf4/0xfd
[ 29.658726] [<ffffffff81139d2a>] __hrtimer_run_queues+0x172/0x32c
[ 29.660120] [<ffffffff8113aca7>] ? SyS_getitimer+0x74/0x74
[ 29.661422] [<ffffffff8113a32a>] hrtimer_interrupt+0x7d/0x149
[ 29.662736] [<ffffffff810868a9>] local_apic_timer_interrupt+0x4b/0x4e
[ 29.664183] [<ffffffff82e341e0>] smp_apic_timer_interrupt+0x2e/0x3e
[ 29.665581] [<ffffffff82e3226c>] apic_timer_interrupt+0x8c/0xa0
[ 29.666933] <EOI> [<ffffffff81092305>] ? native_safe_halt+0x6/0x8
[ 29.668441] [<ffffffff8105f2ee>] default_idle+0x24/0x37
[ 29.669674] [<ffffffff8105f93b>] arch_cpu_idle+0xf/0x11
[ 29.670930] [<ffffffff8110d1c0>] default_idle_call+0x28/0x2f
[ 29.672242] [<ffffffff8110d39b>] cpu_startup_entry+0x17a/0x29a
[ 29.673526] [<ffffffff81085757>] start_secondary+0xe0/0xe3
[ 30.393040] trinity-main (852) used greatest stack depth: 12576 bytes left
[ 35.497090] random: nonblocking pool is initialized
[ 73.263306] init: Failed to create pty - disabling logging for job
Thanks,
Ying Huang