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Commit 202461e2 authored by Mike Galbraith's avatar Mike Galbraith Committed by Thomas Gleixner
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tick/broadcast: Prevent deadlock on tick_broadcast_lock 



tick_broadcast_lock is taken from interrupt context, but the following call
chain takes the lock without disabling interrupts:

[   12.703736]  _raw_spin_lock+0x3b/0x50
[   12.703738]  tick_broadcast_control+0x5a/0x1a0
[   12.703742]  intel_idle_cpu_online+0x22/0x100
[   12.703744]  cpuhp_invoke_callback+0x245/0x9d0
[   12.703752]  cpuhp_thread_fun+0x52/0x110
[   12.703754]  smpboot_thread_fn+0x276/0x320

So the following deadlock can happen:

   lock(tick_broadcast_lock);
   <Interrupt>
      lock(tick_broadcast_lock);

intel_idle_cpu_online() is the only place which violates the calling
convention of tick_broadcast_control(). This was caused by the removal of
the smp function call in course of the cpu hotplug rework.

Instead of slapping local_irq_disable/enable() at the call site, we can
relax the calling convention and handle it in the core code, which makes
the whole machinery more robust.

Fixes: 29d7bbad ("intel_idle: Remove superfluous SMP fuction call")
Reported-by: default avatarGabriel C <nix.or.die@gmail.com>
Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Cc: Ruslan Ruslichenko <rruslich@cisco.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: lwn@lwn.net
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: stable <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/1486953115.5912.4.camel@gmx.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7089db84

kernel/time/tick-broadcast.c

+7 −8
Original line number Original line Diff line number Diff line
@@ -347,17 +347,16 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev) 
 *

 *

 * Called when the system enters a state where affected tick devices

 * Called when the system enters a state where affected tick devices

 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.

 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.

 *

 * Called with interrupts disabled, so clockevents_lock is not

 * required here because the local clock event device cannot go away

 * under us.

 */

 */

void tick_broadcast_control(enum tick_broadcast_mode mode)

void tick_broadcast_control(enum tick_broadcast_mode mode)

{

{

	struct clock_event_device *bc, *dev;

	struct clock_event_device *bc, *dev;

	struct tick_device *td;

	struct tick_device *td;

	int cpu, bc_stopped;

	int cpu, bc_stopped;

	unsigned long flags;





	/* Protects also the local clockevent device. */

	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

	td = this_cpu_ptr(&tick_cpu_device);

	td = this_cpu_ptr(&tick_cpu_device);

	dev = td->evtdev;

	dev = td->evtdev;
@@ -365,12 +364,11 @@ void tick_broadcast_control(enum tick_broadcast_mode mode) 
	 * Is the device not affected by the powerstate ?

	 * Is the device not affected by the powerstate ?

	 */

	 */

	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))

	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))

		return;

		goto out;





	if (!tick_device_is_functional(dev))

	if (!tick_device_is_functional(dev))

		return;

		goto out;





	raw_spin_lock(&tick_broadcast_lock);

	cpu = smp_processor_id();

	cpu = smp_processor_id();

	bc = tick_broadcast_device.evtdev;

	bc = tick_broadcast_device.evtdev;

	bc_stopped = cpumask_empty(tick_broadcast_mask);

	bc_stopped = cpumask_empty(tick_broadcast_mask);
@@ -420,7 +418,8 @@ void tick_broadcast_control(enum tick_broadcast_mode mode) 
				tick_broadcast_setup_oneshot(bc);

				tick_broadcast_setup_oneshot(bc);

		}

		}

	}

	}

	raw_spin_unlock(&tick_broadcast_lock);

out:

	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);

}

}

EXPORT_SYMBOL_GPL(tick_broadcast_control);

EXPORT_SYMBOL_GPL(tick_broadcast_control);