[bug report] padata: simplify serialization mechanism

[bug report] padata: simplify serialization mechanism

[Dan Carpenter]

Hello Steffen Klassert,

The patch 5f1a8c1bc724: "padata: simplify serialization mechanism"
from Jul 7, 2010, leads to the following static checker warning:

	kernel/padata.c:243 padata_reorder()
	warn: 'padata' is an error pointer or valid

kernel/padata.c
   231          if (!spin_trylock_bh(&pd->lock))
   232                  return;
   233  
   234          while (1) {
   235                  padata = padata_get_next(pd);
   236  
   237                  /*
   238                   * All reorder queues are empty, or the next object that needs
   239                   * serialization is parallel processed by another cpu and is
   240                   * still on it's way to the cpu's reorder queue, nothing to
   241                   * do for now.
   242                   */
   243                  if (!padata || PTR_ERR(padata) == -EINPROGRESS)
                             ^^^^^^
The comments still say that we sometimes return NULL but we removed that
in 2010.

   244                          break;
   245  
   246                  /*
   247                   * This cpu has to do the parallel processing of the next
   248                   * object. It's waiting in the cpu's parallelization queue,
   249                   * so exit immediately.
   250                   */
   251                  if (PTR_ERR(padata) == -ENODATA) {
   252                          del_timer(&pd->timer);
   253                          spin_unlock_bh(&pd->lock);
   254                          return;
   255                  }

regards,
dan carpenter

[PATCH] padata: get_next is never NULL

[Jason A. Donenfeld]

Per Dan's static checker warning, the code that returns NULL was removed
in 2010, so this patch updates the comments and fixes the code
assumptions.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
---
 kernel/padata.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/kernel/padata.c b/kernel/padata.c
index f1aef1639204..ac8f1e524836 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -154,8 +154,6 @@ EXPORT_SYMBOL(padata_do_parallel);
  * A pointer to the control struct of the next object that needs
  * serialization, if present in one of the percpu reorder queues.
  *
- * NULL, if all percpu reorder queues are empty.
- *
  * -EINPROGRESS, if the next object that needs serialization will
  *  be parallel processed by another cpu and is not yet present in
  *  the cpu's reorder queue.
@@ -182,8 +180,6 @@ static struct padata_priv *padata_get_next(struct parallel_data *pd)
 	cpu = padata_index_to_cpu(pd, next_index);
 	next_queue = per_cpu_ptr(pd->pqueue, cpu);
 
-	padata = NULL;
-
 	reorder = &next_queue->reorder;
 
 	spin_lock(&reorder->lock);
@@ -235,12 +231,11 @@ static void padata_reorder(struct parallel_data *pd)
 		padata = padata_get_next(pd);
 
 		/*
-		 * All reorder queues are empty, or the next object that needs
-		 * serialization is parallel processed by another cpu and is
-		 * still on it's way to the cpu's reorder queue, nothing to
-		 * do for now.
+		 * If the next object that needs serialization is parallel
+		 * processed by another cpu and is still on it's way to the
+		 * cpu's reorder queue, nothing to do for now.
 		 */
-		if (!padata || PTR_ERR(padata) == -EINPROGRESS)
+		if (PTR_ERR(padata) == -EINPROGRESS)
 			break;
 
 		/*
-- 
2.12.2

Re: [PATCH] padata: get_next is never NULL

[Steffen Klassert]

On Wed, Apr 12, 2017 at 10:40:19AM +0200, Jason A. Donenfeld wrote:
> Per Dan's static checker warning, the code that returns NULL was removed
> in 2010, so this patch updates the comments and fixes the code
> assumptions.
> 
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

This looks ok,

Acked-by: Steffen Klassert <steffen.klassert@secunet.com>