Commit 202461e2 authored by Mike Galbraith's avatar Mike Galbraith Committed by Thomas Gleixner

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.deSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 7089db84
...@@ -347,17 +347,16 @@ static void tick_handle_periodic_broadcast(struct clock_event_device *dev) ...@@ -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) ...@@ -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) ...@@ -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);
......
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