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Commit d3fdaed9 authored by Hugh Dickins's avatar Hugh Dickins Committed by Paul Mackerras
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[POWERPC] Fix smp_call_function to be preempt-safe 



smp_call_function_map() was not safe against preemption to another
cpu: its test for removing self from map was outside the spinlock.
Rearrange it a little to fix that.

smp_call_function_single() was also wrong: now get_cpu() before
excluding self, as other architectures do.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent d2579053

arch/powerpc/kernel/smp.c

+18 −16
Original line number Diff line number Diff line
@@ -201,13 +201,6 @@ int smp_call_function_map(void (*func) (void *info), void *info, int nonatomic, 
	/* Can deadlock when called with interrupts disabled */

	WARN_ON(irqs_disabled());



	/* remove 'self' from the map */

	if (cpu_isset(smp_processor_id(), map))

		cpu_clear(smp_processor_id(), map);



	/* sanity check the map, remove any non-online processors. */

	cpus_and(map, map, cpu_online_map);



	if (unlikely(smp_ops == NULL))

		return ret;
@@ -222,10 +215,17 @@ int smp_call_function_map(void (*func) (void *info), void *info, int nonatomic, 
	/* Must grab online cpu count with preempt disabled, otherwise

	 * it can change. */

	num_cpus = num_online_cpus() - 1;

	if (!num_cpus || cpus_empty(map)) {

		ret = 0;

		goto out;

	}

	if (!num_cpus)

		goto done;



	/* remove 'self' from the map */

	if (cpu_isset(smp_processor_id(), map))

		cpu_clear(smp_processor_id(), map);



	/* sanity check the map, remove any non-online processors. */

	cpus_and(map, map, cpu_online_map);

	if (cpus_empty(map))

		goto done;



	call_data = &data;

	smp_wmb();
@@ -263,6 +263,7 @@ int smp_call_function_map(void (*func) (void *info), void *info, int nonatomic, 
		}

	}



 done:

	ret = 0;



 out:
@@ -283,15 +284,16 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info, int 
			int wait)

{

	cpumask_t map = CPU_MASK_NONE;

	int ret = -EBUSY;



	if (!cpu_online(cpu))

		return -EINVAL;



	if (cpu == smp_processor_id())

		return -EBUSY;



	cpu_set(cpu, map);

	return smp_call_function_map(func,info,nonatomic,wait,map);

	if (cpu != get_cpu())

		ret = smp_call_function_map(func,info,nonatomic,wait,map);

	put_cpu();

	return ret;

}

EXPORT_SYMBOL(smp_call_function_single);