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Commit 5f160126 authored by Stuart Hayes's avatar Stuart Hayes Committed by Len Brown
Browse files

acpi_pad: fix power_saving thread deadlock 

The acpi_pad driver can get stuck in destroy_power_saving_task()
waiting for kthread_stop() to stop a power_saving thread.  The problem
is that the isolated_cpus_lock mutex is owned when
destroy_power_saving_task() calls kthread_stop(), which waits for a
power_saving thread to end, and the power_saving thread tries to
acquire the isolated_cpus_lock when it calls round_robin_cpu().  This
patch fixes the issue by making round_robin_cpu() use its own mutex.

https://bugzilla.kernel.org/show_bug.cgi?id=42981



Cc: stable@vger.kernel.org
Signed-off-by: default avatarStuart Hayes <Stuart_Hayes@Dell.com>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 76e10d15

drivers/acpi/acpi_pad.c

+4 −3
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
#define ACPI_PROCESSOR_AGGREGATOR_DEVICE_NAME "Processor Aggregator"

#define ACPI_PROCESSOR_AGGREGATOR_NOTIFY 0x80

static DEFINE_MUTEX(isolated_cpus_lock);

static DEFINE_MUTEX(round_robin_lock);



static unsigned long power_saving_mwait_eax;
@@ -107,7 +108,7 @@ static void round_robin_cpu(unsigned int tsk_index) 
	if (!alloc_cpumask_var(&tmp, GFP_KERNEL))

		return;



	mutex_lock(&isolated_cpus_lock);

	mutex_lock(&round_robin_lock);

	cpumask_clear(tmp);

	for_each_cpu(cpu, pad_busy_cpus)

		cpumask_or(tmp, tmp, topology_thread_cpumask(cpu));
@@ -116,7 +117,7 @@ static void round_robin_cpu(unsigned int tsk_index) 
	if (cpumask_empty(tmp))

		cpumask_andnot(tmp, cpu_online_mask, pad_busy_cpus);

	if (cpumask_empty(tmp)) {

		mutex_unlock(&isolated_cpus_lock);

		mutex_unlock(&round_robin_lock);

		return;

	}

	for_each_cpu(cpu, tmp) {
@@ -131,7 +132,7 @@ static void round_robin_cpu(unsigned int tsk_index) 
	tsk_in_cpu[tsk_index] = preferred_cpu;

	cpumask_set_cpu(preferred_cpu, pad_busy_cpus);

	cpu_weight[preferred_cpu]++;

	mutex_unlock(&isolated_cpus_lock);

	mutex_unlock(&round_robin_lock);



	set_cpus_allowed_ptr(current, cpumask_of(preferred_cpu));

}