Commit 94e2cc4d authored Sep 21, 2017 by Sebastian Andrzej Siewior Committed by Alex Williamson Nov 06, 2017

iommu/iova: Use raw_cpu_ptr() instead of get_cpu_ptr() for ->fq



get_cpu_ptr() disabled preemption and returns the ->fq object of the
current CPU. raw_cpu_ptr() does the same except that it not disable
preemption which means the scheduler can move it to another CPU after it
obtained the per-CPU object.
In this case this is not bad because the data structure itself is
protected with a spin_lock. This change shouldn't matter however on RT
it does because the sleeping lock can't be accessed with disabled
preemption.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org
Reported-by:  <vinadhy@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

parent a5934725

drivers/iommu/iova.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -542,7 +542,7 @@ void queue_iova(struct iova_domain *iovad,
		unsigned long pfn, unsigned long pages,
		unsigned long data)
		{
		struct iova_fq *fq = get_cpu_ptr(iovad->fq);
		struct iova_fq *fq = raw_cpu_ptr(iovad->fq);
		unsigned long flags;
		unsigned idx;

		@@ -572,8 +572,6 @@ void queue_iova(struct iova_domain *iovad,
		if (atomic_cmpxchg(&iovad->fq_timer_on, 0, 1) == 0)
		mod_timer(&iovad->fq_timer,
		jiffies + msecs_to_jiffies(IOVA_FQ_TIMEOUT));

		put_cpu_ptr(iovad->fq);
		}
		EXPORT_SYMBOL_GPL(queue_iova);

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