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Message-Id: <20190527143932.GA10527@linux.ibm.com>
Date: Mon, 27 May 2019 07:39:32 -0700
From: "Paul E. McKenney" <paulmck@...ux.ibm.com>
To: fweisbec@...il.com, tglx@...utronix.de, mingo@...nel.org
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] time/tick-broadcast: Fix tick_broadcast_offline() lockdep
complaint
The TASKS03 and TREE04 rcutorture scenarios produce the following
lockdep complaint:
================================
WARNING: inconsistent lock state
5.2.0-rc1+ #513 Not tainted
--------------------------------
inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
migration/1/14 [HC0[0]:SC0[0]:HE1:SE1] takes:
(____ptrval____) (tick_broadcast_lock){?...}, at: tick_broadcast_offline+0xf/0x70
{IN-HARDIRQ-W} state was registered at:
lock_acquire+0xb0/0x1c0
_raw_spin_lock_irqsave+0x3c/0x50
tick_broadcast_switch_to_oneshot+0xd/0x40
tick_switch_to_oneshot+0x4f/0xd0
hrtimer_run_queues+0xf3/0x130
run_local_timers+0x1c/0x50
update_process_times+0x1c/0x50
tick_periodic+0x26/0xc0
tick_handle_periodic+0x1a/0x60
smp_apic_timer_interrupt+0x80/0x2a0
apic_timer_interrupt+0xf/0x20
_raw_spin_unlock_irqrestore+0x4e/0x60
rcu_nocb_gp_kthread+0x15d/0x590
kthread+0xf3/0x130
ret_from_fork+0x3a/0x50
irq event stamp: 171
hardirqs last enabled at (171): [<ffffffff8a201a37>] trace_hardirqs_on_thunk+0x1a/0x1c
hardirqs last disabled at (170): [<ffffffff8a201a53>] trace_hardirqs_off_thunk+0x1a/0x1c
softirqs last enabled at (0): [<ffffffff8a264ee0>] copy_process.part.56+0x650/0x1cb0
softirqs last disabled at (0): [<0000000000000000>] 0x0
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(tick_broadcast_lock);
<Interrupt>
lock(tick_broadcast_lock);
*** DEADLOCK ***
1 lock held by migration/1/14:
#0: (____ptrval____) (clockevents_lock){+.+.}, at: tick_offline_cpu+0xf/0x30
stack backtrace:
CPU: 1 PID: 14 Comm: migration/1 Not tainted 5.2.0-rc1+ #513
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Bochs 01/01/2011
Call Trace:
dump_stack+0x5e/0x8b
print_usage_bug+0x1fc/0x216
? print_shortest_lock_dependencies+0x1b0/0x1b0
mark_lock+0x1f2/0x280
__lock_acquire+0x1e0/0x18f0
? __lock_acquire+0x21b/0x18f0
? _raw_spin_unlock_irqrestore+0x4e/0x60
lock_acquire+0xb0/0x1c0
? tick_broadcast_offline+0xf/0x70
_raw_spin_lock+0x33/0x40
? tick_broadcast_offline+0xf/0x70
tick_broadcast_offline+0xf/0x70
tick_offline_cpu+0x16/0x30
take_cpu_down+0x7d/0xa0
multi_cpu_stop+0xa2/0xe0
? cpu_stop_queue_work+0xc0/0xc0
cpu_stopper_thread+0x6d/0x100
smpboot_thread_fn+0x169/0x240
kthread+0xf3/0x130
? sort_range+0x20/0x20
? kthread_cancel_delayed_work_sync+0x10/0x10
ret_from_fork+0x3a/0x50
It turns out that tick_broadcast_offline() can be invoked with interrupts
enabled, so this commit fixes this issue by replacing the raw_spin_lock()
with raw_spin_lock_irqsave().
Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index e51778c312f1..1daf77020230 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -454,12 +454,14 @@ static void tick_shutdown_broadcast(void)
*/
void tick_broadcast_offline(unsigned int cpu)
{
- raw_spin_lock(&tick_broadcast_lock);
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
cpumask_clear_cpu(cpu, tick_broadcast_mask);
cpumask_clear_cpu(cpu, tick_broadcast_on);
tick_broadcast_oneshot_offline(cpu);
tick_shutdown_broadcast();
- raw_spin_unlock(&tick_broadcast_lock);
+ raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
}
#endif
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