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Commit 350ef88e authored by Mathias Krause's avatar Mathias Krause Committed by Herbert Xu
Browse files

padata: ensure padata_do_serial() runs on the correct CPU 



If the algorithm we're parallelizing is asynchronous we might change
CPUs between padata_do_parallel() and padata_do_serial(). However, we
don't expect this to happen as we need to enqueue the padata object into
the per-cpu reorder queue we took it from, i.e. the same-cpu's parallel
queue.

Ensure we're not switching CPUs for a given padata object by tracking
the CPU within the padata object. If the serial callback gets called on
the wrong CPU, defer invoking padata_reorder() via a kernel worker on
the CPU we're expected to run on.

Signed-off-by: default avatarMathias Krause <minipli@googlemail.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent cf5868c8

include/linux/padata.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -37,6 +37,7 @@ 
 * @list: List entry, to attach to the padata lists.

 * @list: List entry, to attach to the padata lists.

 * @pd: Pointer to the internal control structure.

 * @pd: Pointer to the internal control structure.

 * @cb_cpu: Callback cpu for serializatioon.

 * @cb_cpu: Callback cpu for serializatioon.

 * @cpu: Cpu for parallelization.

 * @seq_nr: Sequence number of the parallelized data object.

 * @seq_nr: Sequence number of the parallelized data object.

 * @info: Used to pass information from the parallel to the serial function.

 * @info: Used to pass information from the parallel to the serial function.

 * @parallel: Parallel execution function.

 * @parallel: Parallel execution function.
@@ -46,6 +47,7 @@ struct padata_priv { 
	struct list_head	list;

	struct list_head	list;

	struct parallel_data	*pd;

	struct parallel_data	*pd;

	int			cb_cpu;

	int			cb_cpu;

	int			cpu;

	int			info;

	int			info;

	void                    (*parallel)(struct padata_priv *padata);

	void                    (*parallel)(struct padata_priv *padata);

	void                    (*serial)(struct padata_priv *padata);

	void                    (*serial)(struct padata_priv *padata);

kernel/padata.c

+19 −1
Original line number Original line Diff line number Diff line
@@ -131,6 +131,7 @@ int padata_do_parallel(struct padata_instance *pinst, 
	padata->cb_cpu = cb_cpu;

	padata->cb_cpu = cb_cpu;





	target_cpu = padata_cpu_hash(pd);

	target_cpu = padata_cpu_hash(pd);

	padata->cpu = target_cpu;

	queue = per_cpu_ptr(pd->pqueue, target_cpu);

	queue = per_cpu_ptr(pd->pqueue, target_cpu);





	spin_lock(&queue->parallel.lock);

	spin_lock(&queue->parallel.lock);
@@ -363,10 +364,21 @@ void padata_do_serial(struct padata_priv *padata) 
	int cpu;

	int cpu;

	struct padata_parallel_queue *pqueue;

	struct padata_parallel_queue *pqueue;

	struct parallel_data *pd;

	struct parallel_data *pd;

	int reorder_via_wq = 0;





	pd = padata->pd;

	pd = padata->pd;





	cpu = get_cpu();

	cpu = get_cpu();



	/* We need to run on the same CPU padata_do_parallel(.., padata, ..)

	 * was called on -- or, at least, enqueue the padata object into the

	 * correct per-cpu queue.

	 */

	if (cpu != padata->cpu) {

		reorder_via_wq = 1;

		cpu = padata->cpu;

	}



	pqueue = per_cpu_ptr(pd->pqueue, cpu);

	pqueue = per_cpu_ptr(pd->pqueue, cpu);





	spin_lock(&pqueue->reorder.lock);

	spin_lock(&pqueue->reorder.lock);
@@ -376,6 +388,12 @@ void padata_do_serial(struct padata_priv *padata) 




	put_cpu();

	put_cpu();





	/* If we're running on the wrong CPU, call padata_reorder() via a

	 * kernel worker.

	 */

	if (reorder_via_wq)

		queue_work_on(cpu, pd->pinst->wq, &pqueue->reorder_work);

	else

		padata_reorder(pd);

		padata_reorder(pd);

}

}

EXPORT_SYMBOL(padata_do_serial);

EXPORT_SYMBOL(padata_do_serial);