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* [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
@ 2016-08-09 15:16 ` ira.weiny
  0 siblings, 0 replies; 10+ messages in thread
From: ira.weiny @ 2016-08-09 15:16 UTC (permalink / raw)
  To: dledford; +Cc: linux-rdma, Mike Marciniszyn, Ira Weiny, stable

From: Mike Marciniszyn <mike.marciniszyn@intel.com>

The qp init function does a kzalloc() while holding the RCU
lock that encounters the following warning with a debug kernel
when a cat of the qp_stats is done:

[  231.723948] rcu_scheduler_active = 1, debug_locks = 0
[  231.731939] 3 locks held by cat/11355:
[  231.736492]  #0:  (debugfs_srcu){......}, at: [<ffffffff813001a5>] debugfs_use_file_start+0x5/0x90
[  231.746955]  #1:  (&p->lock){+.+.+.}, at: [<ffffffff81289a6c>] seq_read+0x4c/0x3c0
[  231.755873]  #2:  (rcu_read_lock){......}, at: [<ffffffffa0a0c535>] _qp_stats_seq_start+0x5/0xd0 [hfi1]
[  231.766862]

The init functions do an implicit next which requires the rcu read lock
before the kzalloc().

Fix for both drivers is to change the scope of the init function to only
do the allocation and the initialization of the just allocated iter.

The implict next is moved back into the respective start functions to fix
the issue.


Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
CC: <stable@vger.kernel.org> # 4.6.x-
---
 drivers/infiniband/hw/hfi1/debugfs.c    | 17 ++++++++++++-----
 drivers/infiniband/hw/hfi1/qp.c         |  4 ----
 drivers/infiniband/hw/qib/qib_debugfs.c | 16 ++++++++++++----
 drivers/infiniband/hw/qib/qib_qp.c      |  4 ----
 4 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
index dbab9d9cc288..c35bef8dd5aa 100644
--- a/drivers/infiniband/hw/hfi1/debugfs.c
+++ b/drivers/infiniband/hw/hfi1/debugfs.c
@@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
 DEBUGFS_FILE_OPS(ctx_stats);
 
 static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
-__acquires(RCU)
+	__acquires(RCU)
 {
 	struct qp_iter *iter;
 	loff_t n = *pos;
 
-	rcu_read_lock();
 	iter = qp_iter_init(s->private);
+
+	/* stop calls rcu_read_unlock */
+	rcu_read_lock();
+
 	if (!iter)
 		return NULL;
 
-	while (n--) {
+	if (qp_iter_next(iter)) {
+		kfree(iter);
+		return NULL;
+	}
+	while (n--)
 		if (qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
 
 	return iter;
 }
 
 static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 				loff_t *pos)
+	__must_hold(RCU)
 {
 	struct qp_iter *iter = iter_ptr;
 
@@ -259,7 +266,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
-__releases(RCU)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
diff --git a/drivers/infiniband/hw/hfi1/qp.c b/drivers/infiniband/hw/hfi1/qp.c
index a5aa3517e7d5..4e4d8317c281 100644
--- a/drivers/infiniband/hw/hfi1/qp.c
+++ b/drivers/infiniband/hw/hfi1/qp.c
@@ -656,10 +656,6 @@ struct qp_iter *qp_iter_init(struct hfi1_ibdev *dev)
 
 	iter->dev = dev;
 	iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
-	if (qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }
diff --git a/drivers/infiniband/hw/qib/qib_debugfs.c b/drivers/infiniband/hw/qib/qib_debugfs.c
index 5e75b43c596b..07059c08c170 100644
--- a/drivers/infiniband/hw/qib/qib_debugfs.c
+++ b/drivers/infiniband/hw/qib/qib_debugfs.c
@@ -189,27 +189,34 @@ static int _ctx_stats_seq_show(struct seq_file *s, void *v)
 DEBUGFS_FILE(ctx_stats)
 
 static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
+	__acquires(RCU)
 {
 	struct qib_qp_iter *iter;
 	loff_t n = *pos;
 
-	rcu_read_lock();
 	iter = qib_qp_iter_init(s->private);
+
+	/* stop calls rcu_read_unlock */
+	rcu_read_lock();
+
 	if (!iter)
 		return NULL;
 
-	while (n--) {
+	if (qib_qp_iter_next(iter)) {
+		kfree(iter);
+		return NULL;
+	}
+	while (n--)
 		if (qib_qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
-
 	return iter;
 }
 
 static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 				   loff_t *pos)
+	__must_hold(RCU)
 {
 	struct qib_qp_iter *iter = iter_ptr;
 
@@ -224,6 +231,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c
index 9cc0aae1d781..f9b8cd2354d1 100644
--- a/drivers/infiniband/hw/qib/qib_qp.c
+++ b/drivers/infiniband/hw/qib/qib_qp.c
@@ -573,10 +573,6 @@ struct qib_qp_iter *qib_qp_iter_init(struct qib_ibdev *dev)
 		return NULL;
 
 	iter->dev = dev;
-	if (qib_qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }
-- 
1.8.2

^ permalink raw reply related	[flat|nested] 10+ messages in thread
* [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
@ 2016-08-09 15:16 ` ira.weiny
  0 siblings, 0 replies; 10+ messages in thread
From: ira.weiny @ 2016-08-09 15:16 UTC (permalink / raw)
  To: dledford; +Cc: linux-rdma, Mike Marciniszyn, Ira Weiny, stable

From: Mike Marciniszyn <mike.marciniszyn@intel.com>

The qp init function does a kzalloc() while holding the RCU
lock that encounters the following warning with a debug kernel
when a cat of the qp_stats is done:

[  231.723948] rcu_scheduler_active = 1, debug_locks = 0
[  231.731939] 3 locks held by cat/11355:
[  231.736492]  #0:  (debugfs_srcu){......}, at: [<ffffffff813001a5>] debugfs_use_file_start+0x5/0x90
[  231.746955]  #1:  (&p->lock){+.+.+.}, at: [<ffffffff81289a6c>] seq_read+0x4c/0x3c0
[  231.755873]  #2:  (rcu_read_lock){......}, at: [<ffffffffa0a0c535>] _qp_stats_seq_start+0x5/0xd0 [hfi1]
[  231.766862]

The init functions do an implicit next which requires the rcu read lock
before the kzalloc().

Fix for both drivers is to change the scope of the init function to only
do the allocation and the initialization of the just allocated iter.

The implict next is moved back into the respective start functions to fix
the issue.


Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
CC: <stable@vger.kernel.org> # 4.6.x-
---
 drivers/infiniband/hw/hfi1/debugfs.c    | 17 ++++++++++++-----
 drivers/infiniband/hw/hfi1/qp.c         |  4 ----
 drivers/infiniband/hw/qib/qib_debugfs.c | 16 ++++++++++++----
 drivers/infiniband/hw/qib/qib_qp.c      |  4 ----
 4 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
index dbab9d9cc288..c35bef8dd5aa 100644
--- a/drivers/infiniband/hw/hfi1/debugfs.c
+++ b/drivers/infiniband/hw/hfi1/debugfs.c
@@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
 DEBUGFS_FILE_OPS(ctx_stats);
 
 static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
-__acquires(RCU)
+	__acquires(RCU)
 {
 	struct qp_iter *iter;
 	loff_t n = *pos;
 
-	rcu_read_lock();
 	iter = qp_iter_init(s->private);
+
+	/* stop calls rcu_read_unlock */
+	rcu_read_lock();
+
 	if (!iter)
 		return NULL;
 
-	while (n--) {
+	if (qp_iter_next(iter)) {
+		kfree(iter);
+		return NULL;
+	}
+	while (n--)
 		if (qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
 
 	return iter;
 }
 
 static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 				loff_t *pos)
+	__must_hold(RCU)
 {
 	struct qp_iter *iter = iter_ptr;
 
@@ -259,7 +266,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
-__releases(RCU)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
diff --git a/drivers/infiniband/hw/hfi1/qp.c b/drivers/infiniband/hw/hfi1/qp.c
index a5aa3517e7d5..4e4d8317c281 100644
--- a/drivers/infiniband/hw/hfi1/qp.c
+++ b/drivers/infiniband/hw/hfi1/qp.c
@@ -656,10 +656,6 @@ struct qp_iter *qp_iter_init(struct hfi1_ibdev *dev)
 
 	iter->dev = dev;
 	iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
-	if (qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }
diff --git a/drivers/infiniband/hw/qib/qib_debugfs.c b/drivers/infiniband/hw/qib/qib_debugfs.c
index 5e75b43c596b..07059c08c170 100644
--- a/drivers/infiniband/hw/qib/qib_debugfs.c
+++ b/drivers/infiniband/hw/qib/qib_debugfs.c
@@ -189,27 +189,34 @@ static int _ctx_stats_seq_show(struct seq_file *s, void *v)
 DEBUGFS_FILE(ctx_stats)
 
 static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
+	__acquires(RCU)
 {
 	struct qib_qp_iter *iter;
 	loff_t n = *pos;
 
-	rcu_read_lock();
 	iter = qib_qp_iter_init(s->private);
+
+	/* stop calls rcu_read_unlock */
+	rcu_read_lock();
+
 	if (!iter)
 		return NULL;
 
-	while (n--) {
+	if (qib_qp_iter_next(iter)) {
+		kfree(iter);
+		return NULL;
+	}
+	while (n--)
 		if (qib_qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
-
 	return iter;
 }
 
 static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 				   loff_t *pos)
+	__must_hold(RCU)
 {
 	struct qib_qp_iter *iter = iter_ptr;
 
@@ -224,6 +231,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c
index 9cc0aae1d781..f9b8cd2354d1 100644
--- a/drivers/infiniband/hw/qib/qib_qp.c
+++ b/drivers/infiniband/hw/qib/qib_qp.c
@@ -573,10 +573,6 @@ struct qib_qp_iter *qib_qp_iter_init(struct qib_ibdev *dev)
 		return NULL;
 
 	iter->dev = dev;
-	if (qib_qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }
-- 
1.8.2


^ permalink raw reply related	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
  2016-08-09 15:16 ` ira.weiny
  (?)
@ 2016-08-09 18:11 ` Leon Romanovsky
  2016-08-10  5:51   ` ira.weiny
  -1 siblings, 1 reply; 10+ messages in thread
From: Leon Romanovsky @ 2016-08-09 18:11 UTC (permalink / raw)
  To: ira.weiny; +Cc: dledford, linux-rdma, Mike Marciniszyn, stable

[-- Attachment #1: Type: text/plain, Size: 5494 bytes --]

On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny@intel.com wrote:
> From: Mike Marciniszyn <mike.marciniszyn@intel.com>
> 
> The qp init function does a kzalloc() while holding the RCU
> lock that encounters the following warning with a debug kernel
> when a cat of the qp_stats is done:
> 
> [  231.723948] rcu_scheduler_active = 1, debug_locks = 0
> [  231.731939] 3 locks held by cat/11355:
> [  231.736492]  #0:  (debugfs_srcu){......}, at: [<ffffffff813001a5>] debugfs_use_file_start+0x5/0x90
> [  231.746955]  #1:  (&p->lock){+.+.+.}, at: [<ffffffff81289a6c>] seq_read+0x4c/0x3c0
> [  231.755873]  #2:  (rcu_read_lock){......}, at: [<ffffffffa0a0c535>] _qp_stats_seq_start+0x5/0xd0 [hfi1]
> [  231.766862]
> 
> The init functions do an implicit next which requires the rcu read lock
> before the kzalloc().
> 
> Fix for both drivers is to change the scope of the init function to only
> do the allocation and the initialization of the just allocated iter.
> 
> The implict next is moved back into the respective start functions to fix
> the issue.
> 
> 
> Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
> CC: <stable@vger.kernel.org> # 4.6.x-
> ---
>  drivers/infiniband/hw/hfi1/debugfs.c    | 17 ++++++++++++-----
>  drivers/infiniband/hw/hfi1/qp.c         |  4 ----
>  drivers/infiniband/hw/qib/qib_debugfs.c | 16 ++++++++++++----
>  drivers/infiniband/hw/qib/qib_qp.c      |  4 ----
>  4 files changed, 24 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
> index dbab9d9cc288..c35bef8dd5aa 100644
> --- a/drivers/infiniband/hw/hfi1/debugfs.c
> +++ b/drivers/infiniband/hw/hfi1/debugfs.c
> @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
>  DEBUGFS_FILE_OPS(ctx_stats);
>  
>  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> -__acquires(RCU)
> +	__acquires(RCU)
>  {
>  	struct qp_iter *iter;
>  	loff_t n = *pos;
>  
> -	rcu_read_lock();
>  	iter = qp_iter_init(s->private);
> +
> +	/* stop calls rcu_read_unlock */
> +	rcu_read_lock();

IMHO, it should be placed after your if(!iter) check below.

> +
>  	if (!iter)
>  		return NULL;
>  
> -	while (n--) {
> +	if (qp_iter_next(iter)) {
> +		kfree(iter);
> +		return NULL;
> +	}
> +	while (n--)
>  		if (qp_iter_next(iter)) {
>  			kfree(iter);
>  			return NULL;
>  		}

It looks like you forgot to remove the lines above.

> -	}
>  
>  	return iter;
>  }
>  
>  static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
>  				loff_t *pos)
> +	__must_hold(RCU)
>  {
>  	struct qp_iter *iter = iter_ptr;
>  
> @@ -259,7 +266,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
>  }
>  
>  static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
> -__releases(RCU)
> +	__releases(RCU)
>  {
>  	rcu_read_unlock();
>  }
> diff --git a/drivers/infiniband/hw/hfi1/qp.c b/drivers/infiniband/hw/hfi1/qp.c
> index a5aa3517e7d5..4e4d8317c281 100644
> --- a/drivers/infiniband/hw/hfi1/qp.c
> +++ b/drivers/infiniband/hw/hfi1/qp.c
> @@ -656,10 +656,6 @@ struct qp_iter *qp_iter_init(struct hfi1_ibdev *dev)
>  
>  	iter->dev = dev;
>  	iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
> -	if (qp_iter_next(iter)) {
> -		kfree(iter);
> -		return NULL;
> -	}
>  
>  	return iter;
>  }
> diff --git a/drivers/infiniband/hw/qib/qib_debugfs.c b/drivers/infiniband/hw/qib/qib_debugfs.c
> index 5e75b43c596b..07059c08c170 100644
> --- a/drivers/infiniband/hw/qib/qib_debugfs.c
> +++ b/drivers/infiniband/hw/qib/qib_debugfs.c
> @@ -189,27 +189,34 @@ static int _ctx_stats_seq_show(struct seq_file *s, void *v)
>  DEBUGFS_FILE(ctx_stats)
>  
>  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> +	__acquires(RCU)
>  {
>  	struct qib_qp_iter *iter;
>  	loff_t n = *pos;
>  
> -	rcu_read_lock();
>  	iter = qib_qp_iter_init(s->private);
> +
> +	/* stop calls rcu_read_unlock */
> +	rcu_read_lock();
> +

The same

>  	if (!iter)
>  		return NULL;
>  
> -	while (n--) {
> +	if (qib_qp_iter_next(iter)) {
> +		kfree(iter);
> +		return NULL;
> +	}
> +	while (n--)
>  		if (qib_qp_iter_next(iter)) {
>  			kfree(iter);
>  			return NULL;
>  		}
> -	}
> -

The same

>  	return iter;
>  }
>  
>  static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
>  				   loff_t *pos)
> +	__must_hold(RCU)
>  {
>  	struct qib_qp_iter *iter = iter_ptr;
>  
> @@ -224,6 +231,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
>  }
>  
>  static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
> +	__releases(RCU)
>  {
>  	rcu_read_unlock();
>  }
> diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c
> index 9cc0aae1d781..f9b8cd2354d1 100644
> --- a/drivers/infiniband/hw/qib/qib_qp.c
> +++ b/drivers/infiniband/hw/qib/qib_qp.c
> @@ -573,10 +573,6 @@ struct qib_qp_iter *qib_qp_iter_init(struct qib_ibdev *dev)
>  		return NULL;
>  
>  	iter->dev = dev;
> -	if (qib_qp_iter_next(iter)) {
> -		kfree(iter);
> -		return NULL;
> -	}
>  
>  	return iter;
>  }
> -- 
> 1.8.2
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
  2016-08-09 18:11 ` Leon Romanovsky
@ 2016-08-10  5:51   ` ira.weiny
       [not found]     ` <20160810055151.GB32695-W4f6Xiosr+yv7QzWx2u06xL4W9x8LtSr@public.gmane.org>
  0 siblings, 1 reply; 10+ messages in thread
From: ira.weiny @ 2016-08-10  5:51 UTC (permalink / raw)
  To: Leon Romanovsky; +Cc: dledford, linux-rdma, Mike Marciniszyn, stable

On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
> On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny@intel.com wrote:
> > From: Mike Marciniszyn <mike.marciniszyn@intel.com>
> > 

[snip]

> > diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
> > index dbab9d9cc288..c35bef8dd5aa 100644
> > --- a/drivers/infiniband/hw/hfi1/debugfs.c
> > +++ b/drivers/infiniband/hw/hfi1/debugfs.c
> > @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
> >  DEBUGFS_FILE_OPS(ctx_stats);
> >  
> >  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> > -__acquires(RCU)
> > +	__acquires(RCU)
> >  {
> >  	struct qp_iter *iter;
> >  	loff_t n = *pos;
> >  
> > -	rcu_read_lock();
> >  	iter = qp_iter_init(s->private);
> > +
> > +	/* stop calls rcu_read_unlock */
> > +	rcu_read_lock();
> 
> IMHO, it should be placed after your if(!iter) check below.

I know this seems weird but this makes the rcu locking "balanced".  Returning
NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
move rcu_read_lock we need to maintain state to determine if we called lock or
not.  This is easier.  To me it does seem odd that the sequence operation does
not stop on its own when NULL is returned but that is the way it works.

> 
> > +
> >  	if (!iter)
> >  		return NULL;
> >  
> > -	while (n--) {
> > +	if (qp_iter_next(iter)) {
> > +		kfree(iter);
> > +		return NULL;
> > +	}
> > +	while (n--)
> >  		if (qp_iter_next(iter)) {
> >  			kfree(iter);
> >  			return NULL;
> >  		}
> 
> It looks like you forgot to remove the lines above.

Nope this replaces a call to qp_iter_next which was in qp_iter_init.

As the commit messages says we move the implict next's back into the respective
start functions.

Ira

> 
> > -	}
> >  
> >  	return iter;
> >  }
> >  
> >  static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
> >  				loff_t *pos)
> > +	__must_hold(RCU)
> >  {
> >  	struct qp_iter *iter = iter_ptr;
> >  
> > @@ -259,7 +266,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
> >  }
> >  
> >  static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
> > -__releases(RCU)
> > +	__releases(RCU)
> >  {
> >  	rcu_read_unlock();
> >  }
> > diff --git a/drivers/infiniband/hw/hfi1/qp.c b/drivers/infiniband/hw/hfi1/qp.c
> > index a5aa3517e7d5..4e4d8317c281 100644
> > --- a/drivers/infiniband/hw/hfi1/qp.c
> > +++ b/drivers/infiniband/hw/hfi1/qp.c
> > @@ -656,10 +656,6 @@ struct qp_iter *qp_iter_init(struct hfi1_ibdev *dev)
> >  
> >  	iter->dev = dev;
> >  	iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
> > -	if (qp_iter_next(iter)) {
> > -		kfree(iter);
> > -		return NULL;
> > -	}
> >  
> >  	return iter;
> >  }
> > diff --git a/drivers/infiniband/hw/qib/qib_debugfs.c b/drivers/infiniband/hw/qib/qib_debugfs.c
> > index 5e75b43c596b..07059c08c170 100644
> > --- a/drivers/infiniband/hw/qib/qib_debugfs.c
> > +++ b/drivers/infiniband/hw/qib/qib_debugfs.c
> > @@ -189,27 +189,34 @@ static int _ctx_stats_seq_show(struct seq_file *s, void *v)
> >  DEBUGFS_FILE(ctx_stats)
> >  
> >  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> > +	__acquires(RCU)
> >  {
> >  	struct qib_qp_iter *iter;
> >  	loff_t n = *pos;
> >  
> > -	rcu_read_lock();
> >  	iter = qib_qp_iter_init(s->private);
> > +
> > +	/* stop calls rcu_read_unlock */
> > +	rcu_read_lock();
> > +
> 
> The same
> 
> >  	if (!iter)
> >  		return NULL;
> >  
> > -	while (n--) {
> > +	if (qib_qp_iter_next(iter)) {
> > +		kfree(iter);
> > +		return NULL;
> > +	}
> > +	while (n--)
> >  		if (qib_qp_iter_next(iter)) {
> >  			kfree(iter);
> >  			return NULL;
> >  		}
> > -	}
> > -
> 
> The same
> 
> >  	return iter;
> >  }
> >  
> >  static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
> >  				   loff_t *pos)
> > +	__must_hold(RCU)
> >  {
> >  	struct qib_qp_iter *iter = iter_ptr;
> >  
> > @@ -224,6 +231,7 @@ static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
> >  }
> >  
> >  static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
> > +	__releases(RCU)
> >  {
> >  	rcu_read_unlock();
> >  }
> > diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c
> > index 9cc0aae1d781..f9b8cd2354d1 100644
> > --- a/drivers/infiniband/hw/qib/qib_qp.c
> > +++ b/drivers/infiniband/hw/qib/qib_qp.c
> > @@ -573,10 +573,6 @@ struct qib_qp_iter *qib_qp_iter_init(struct qib_ibdev *dev)
> >  		return NULL;
> >  
> >  	iter->dev = dev;
> > -	if (qib_qp_iter_next(iter)) {
> > -		kfree(iter);
> > -		return NULL;
> > -	}
> >  
> >  	return iter;
> >  }
> > -- 
> > 1.8.2
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
  2016-08-10  5:51   ` ira.weiny
@ 2016-08-10  8:24         ` Leon Romanovsky
  0 siblings, 0 replies; 10+ messages in thread
From: Leon Romanovsky @ 2016-08-10  8:24 UTC (permalink / raw)
  To: ira.weiny
  Cc: dledford-H+wXaHxf7aLQT0dZR+AlfA,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA, Mike Marciniszyn,
	stable-u79uwXL29TY76Z2rM5mHXA

[-- Attachment #1: Type: text/plain, Size: 2203 bytes --]

On Wed, Aug 10, 2016 at 01:51:52AM -0400, ira.weiny wrote:
> On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
> > On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org wrote:
> > > From: Mike Marciniszyn <mike.marciniszyn-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > > 
> 
> [snip]
> 
> > > diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
> > > index dbab9d9cc288..c35bef8dd5aa 100644
> > > --- a/drivers/infiniband/hw/hfi1/debugfs.c
> > > +++ b/drivers/infiniband/hw/hfi1/debugfs.c
> > > @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
> > >  DEBUGFS_FILE_OPS(ctx_stats);
> > >  
> > >  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> > > -__acquires(RCU)
> > > +	__acquires(RCU)
> > >  {
> > >  	struct qp_iter *iter;
> > >  	loff_t n = *pos;
> > >  
> > > -	rcu_read_lock();
> > >  	iter = qp_iter_init(s->private);
> > > +
> > > +	/* stop calls rcu_read_unlock */
> > > +	rcu_read_lock();
> > 
> > IMHO, it should be placed after your if(!iter) check below.
> 
> I know this seems weird but this makes the rcu locking "balanced".  Returning
> NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
> move rcu_read_lock we need to maintain state to determine if we called lock or
> not.  This is easier.  To me it does seem odd that the sequence operation does
> not stop on its own when NULL is returned but that is the way it works.

Thanks for the explanation.

> 
> > 
> > > +
> > >  	if (!iter)
> > >  		return NULL;
> > >  
> > > -	while (n--) {
> > > +	if (qp_iter_next(iter)) {
> > > +		kfree(iter);
> > > +		return NULL;
> > > +	}
> > > +	while (n--)
> > >  		if (qp_iter_next(iter)) {
> > >  			kfree(iter);
> > >  			return NULL;
> > >  		}
> > 
> > It looks like you forgot to remove the lines above.
> 
> Nope this replaces a call to qp_iter_next which was in qp_iter_init.
> 
> As the commit messages says we move the implict next's back into the respective
> start functions.

Did you consider as an option to use do{...}while(...) construction
instead of this duplicated code?

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^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
@ 2016-08-10  8:24         ` Leon Romanovsky
  0 siblings, 0 replies; 10+ messages in thread
From: Leon Romanovsky @ 2016-08-10  8:24 UTC (permalink / raw)
  To: ira.weiny; +Cc: dledford, linux-rdma, Mike Marciniszyn, stable

[-- Attachment #1: Type: text/plain, Size: 2143 bytes --]

On Wed, Aug 10, 2016 at 01:51:52AM -0400, ira.weiny wrote:
> On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
> > On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny@intel.com wrote:
> > > From: Mike Marciniszyn <mike.marciniszyn@intel.com>
> > > 
> 
> [snip]
> 
> > > diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
> > > index dbab9d9cc288..c35bef8dd5aa 100644
> > > --- a/drivers/infiniband/hw/hfi1/debugfs.c
> > > +++ b/drivers/infiniband/hw/hfi1/debugfs.c
> > > @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
> > >  DEBUGFS_FILE_OPS(ctx_stats);
> > >  
> > >  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> > > -__acquires(RCU)
> > > +	__acquires(RCU)
> > >  {
> > >  	struct qp_iter *iter;
> > >  	loff_t n = *pos;
> > >  
> > > -	rcu_read_lock();
> > >  	iter = qp_iter_init(s->private);
> > > +
> > > +	/* stop calls rcu_read_unlock */
> > > +	rcu_read_lock();
> > 
> > IMHO, it should be placed after your if(!iter) check below.
> 
> I know this seems weird but this makes the rcu locking "balanced".  Returning
> NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
> move rcu_read_lock we need to maintain state to determine if we called lock or
> not.  This is easier.  To me it does seem odd that the sequence operation does
> not stop on its own when NULL is returned but that is the way it works.

Thanks for the explanation.

> 
> > 
> > > +
> > >  	if (!iter)
> > >  		return NULL;
> > >  
> > > -	while (n--) {
> > > +	if (qp_iter_next(iter)) {
> > > +		kfree(iter);
> > > +		return NULL;
> > > +	}
> > > +	while (n--)
> > >  		if (qp_iter_next(iter)) {
> > >  			kfree(iter);
> > >  			return NULL;
> > >  		}
> > 
> > It looks like you forgot to remove the lines above.
> 
> Nope this replaces a call to qp_iter_next which was in qp_iter_init.
> 
> As the commit messages says we move the implict next's back into the respective
> start functions.

Did you consider as an option to use do{...}while(...) construction
instead of this duplicated code?

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^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
  2016-08-10  5:51   ` ira.weiny
@ 2016-08-10 10:17         ` Leon Romanovsky
  0 siblings, 0 replies; 10+ messages in thread
From: Leon Romanovsky @ 2016-08-10 10:17 UTC (permalink / raw)
  To: ira.weiny
  Cc: dledford-H+wXaHxf7aLQT0dZR+AlfA,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA, Mike Marciniszyn,
	stable-u79uwXL29TY76Z2rM5mHXA

[-- Attachment #1: Type: text/plain, Size: 2151 bytes --]

On Wed, Aug 10, 2016 at 01:51:52AM -0400, ira.weiny wrote:
> On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
> > On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org wrote:
> > > From: Mike Marciniszyn <mike.marciniszyn-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > > 
> 
> [snip]
> 
> > > diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
> > > index dbab9d9cc288..c35bef8dd5aa 100644
> > > --- a/drivers/infiniband/hw/hfi1/debugfs.c
> > > +++ b/drivers/infiniband/hw/hfi1/debugfs.c
> > > @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
> > >  DEBUGFS_FILE_OPS(ctx_stats);
> > >  
> > >  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> > > -__acquires(RCU)
> > > +	__acquires(RCU)
> > >  {
> > >  	struct qp_iter *iter;
> > >  	loff_t n = *pos;
> > >  
> > > -	rcu_read_lock();
> > >  	iter = qp_iter_init(s->private);
> > > +
> > > +	/* stop calls rcu_read_unlock */
> > > +	rcu_read_lock();
> > 
> > IMHO, it should be placed after your if(!iter) check below.
> 
> I know this seems weird but this makes the rcu locking "balanced".  Returning
> NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
> move rcu_read_lock we need to maintain state to determine if we called lock or
> not.  This is easier.  To me it does seem odd that the sequence operation does
> not stop on its own when NULL is returned but that is the way it works.
> 
> > 
> > > +
> > >  	if (!iter)
> > >  		return NULL;
> > >  
> > > -	while (n--) {
> > > +	if (qp_iter_next(iter)) {
> > > +		kfree(iter);
> > > +		return NULL;
> > > +	}
> > > +	while (n--)
> > >  		if (qp_iter_next(iter)) {
> > >  			kfree(iter);
> > >  			return NULL;
> > >  		}
> > 
> > It looks like you forgot to remove the lines above.
> 
> Nope this replaces a call to qp_iter_next which was in qp_iter_init.
> 
> As the commit messages says we move the implict next's back into the respective
> start functions.

Did you consider to use do{..}while(..) construction instead of
duplicating code?

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^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
@ 2016-08-10 10:17         ` Leon Romanovsky
  0 siblings, 0 replies; 10+ messages in thread
From: Leon Romanovsky @ 2016-08-10 10:17 UTC (permalink / raw)
  To: ira.weiny; +Cc: dledford, linux-rdma, Mike Marciniszyn, stable

[-- Attachment #1: Type: text/plain, Size: 2091 bytes --]

On Wed, Aug 10, 2016 at 01:51:52AM -0400, ira.weiny wrote:
> On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
> > On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny@intel.com wrote:
> > > From: Mike Marciniszyn <mike.marciniszyn@intel.com>
> > > 
> 
> [snip]
> 
> > > diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
> > > index dbab9d9cc288..c35bef8dd5aa 100644
> > > --- a/drivers/infiniband/hw/hfi1/debugfs.c
> > > +++ b/drivers/infiniband/hw/hfi1/debugfs.c
> > > @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
> > >  DEBUGFS_FILE_OPS(ctx_stats);
> > >  
> > >  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
> > > -__acquires(RCU)
> > > +	__acquires(RCU)
> > >  {
> > >  	struct qp_iter *iter;
> > >  	loff_t n = *pos;
> > >  
> > > -	rcu_read_lock();
> > >  	iter = qp_iter_init(s->private);
> > > +
> > > +	/* stop calls rcu_read_unlock */
> > > +	rcu_read_lock();
> > 
> > IMHO, it should be placed after your if(!iter) check below.
> 
> I know this seems weird but this makes the rcu locking "balanced".  Returning
> NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
> move rcu_read_lock we need to maintain state to determine if we called lock or
> not.  This is easier.  To me it does seem odd that the sequence operation does
> not stop on its own when NULL is returned but that is the way it works.
> 
> > 
> > > +
> > >  	if (!iter)
> > >  		return NULL;
> > >  
> > > -	while (n--) {
> > > +	if (qp_iter_next(iter)) {
> > > +		kfree(iter);
> > > +		return NULL;
> > > +	}
> > > +	while (n--)
> > >  		if (qp_iter_next(iter)) {
> > >  			kfree(iter);
> > >  			return NULL;
> > >  		}
> > 
> > It looks like you forgot to remove the lines above.
> 
> Nope this replaces a call to qp_iter_next which was in qp_iter_init.
> 
> As the commit messages says we move the implict next's back into the respective
> start functions.

Did you consider to use do{..}while(..) construction instead of
duplicating code?

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^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
  2016-08-10  5:51   ` ira.weiny
@ 2016-08-22 18:21         ` Doug Ledford
  0 siblings, 0 replies; 10+ messages in thread
From: Doug Ledford @ 2016-08-22 18:21 UTC (permalink / raw)
  To: ira.weiny, Leon Romanovsky
  Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA, Mike Marciniszyn,
	stable-u79uwXL29TY76Z2rM5mHXA


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On 8/10/2016 1:51 AM, ira.weiny wrote:
> On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
>> On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org wrote:
>>> From: Mike Marciniszyn <mike.marciniszyn-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>>>
> 
> [snip]
> 
>>> diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
>>> index dbab9d9cc288..c35bef8dd5aa 100644
>>> --- a/drivers/infiniband/hw/hfi1/debugfs.c
>>> +++ b/drivers/infiniband/hw/hfi1/debugfs.c
>>> @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
>>>  DEBUGFS_FILE_OPS(ctx_stats);
>>>  
>>>  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
>>> -__acquires(RCU)
>>> +	__acquires(RCU)
>>>  {
>>>  	struct qp_iter *iter;
>>>  	loff_t n = *pos;
>>>  
>>> -	rcu_read_lock();
>>>  	iter = qp_iter_init(s->private);
>>> +
>>> +	/* stop calls rcu_read_unlock */
>>> +	rcu_read_lock();
>>
>> IMHO, it should be placed after your if(!iter) check below.
> 
> I know this seems weird but this makes the rcu locking "balanced".  Returning
> NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
> move rcu_read_lock we need to maintain state to determine if we called lock or
> not.  This is easier.  To me it does seem odd that the sequence operation does
> not stop on its own when NULL is returned but that is the way it works.
> 
>>
>>> +
>>>  	if (!iter)
>>>  		return NULL;
>>>  
>>> -	while (n--) {
>>> +	if (qp_iter_next(iter)) {
>>> +		kfree(iter);
>>> +		return NULL;
>>> +	}
>>> +	while (n--)
>>>  		if (qp_iter_next(iter)) {
>>>  			kfree(iter);
>>>  			return NULL;
>>>  		}
>>
>> It looks like you forgot to remove the lines above.
> 
> Nope this replaces a call to qp_iter_next which was in qp_iter_init.
> 
> As the commit messages says we move the implict next's back into the respective
> start functions.
> 
> Ira

Thanks, applied.


-- 
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
    GPG Key ID: 0E572FDD


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^ permalink raw reply	[flat|nested] 10+ messages in thread
* Re: [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
@ 2016-08-22 18:21         ` Doug Ledford
  0 siblings, 0 replies; 10+ messages in thread
From: Doug Ledford @ 2016-08-22 18:21 UTC (permalink / raw)
  To: ira.weiny, Leon Romanovsky; +Cc: linux-rdma, Mike Marciniszyn, stable


[-- Attachment #1.1: Type: text/plain, Size: 2009 bytes --]

On 8/10/2016 1:51 AM, ira.weiny wrote:
> On Tue, Aug 09, 2016 at 09:11:46PM +0300, Leon Romanovsky wrote:
>> On Tue, Aug 09, 2016 at 11:16:26AM -0400, ira.weiny@intel.com wrote:
>>> From: Mike Marciniszyn <mike.marciniszyn@intel.com>
>>>
> 
> [snip]
> 
>>> diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
>>> index dbab9d9cc288..c35bef8dd5aa 100644
>>> --- a/drivers/infiniband/hw/hfi1/debugfs.c
>>> +++ b/drivers/infiniband/hw/hfi1/debugfs.c
>>> @@ -223,28 +223,35 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
>>>  DEBUGFS_FILE_OPS(ctx_stats);
>>>  
>>>  static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
>>> -__acquires(RCU)
>>> +	__acquires(RCU)
>>>  {
>>>  	struct qp_iter *iter;
>>>  	loff_t n = *pos;
>>>  
>>> -	rcu_read_lock();
>>>  	iter = qp_iter_init(s->private);
>>> +
>>> +	/* stop calls rcu_read_unlock */
>>> +	rcu_read_lock();
>>
>> IMHO, it should be placed after your if(!iter) check below.
> 
> I know this seems weird but this makes the rcu locking "balanced".  Returning
> NULL here still calls "stop" which is going to call rcu_read_unlock.  If we
> move rcu_read_lock we need to maintain state to determine if we called lock or
> not.  This is easier.  To me it does seem odd that the sequence operation does
> not stop on its own when NULL is returned but that is the way it works.
> 
>>
>>> +
>>>  	if (!iter)
>>>  		return NULL;
>>>  
>>> -	while (n--) {
>>> +	if (qp_iter_next(iter)) {
>>> +		kfree(iter);
>>> +		return NULL;
>>> +	}
>>> +	while (n--)
>>>  		if (qp_iter_next(iter)) {
>>>  			kfree(iter);
>>>  			return NULL;
>>>  		}
>>
>> It looks like you forgot to remove the lines above.
> 
> Nope this replaces a call to qp_iter_next which was in qp_iter_init.
> 
> As the commit messages says we move the implict next's back into the respective
> start functions.
> 
> Ira

Thanks, applied.


-- 
Doug Ledford <dledford@redhat.com>
    GPG Key ID: 0E572FDD


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^ permalink raw reply	[flat|nested] 10+ messages in thread
end of thread, other threads:[~2016-08-22 18:22 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-08-09 15:16 [PATCH] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held ira.weiny
2016-08-09 15:16 ` ira.weiny
2016-08-09 18:11 ` Leon Romanovsky
2016-08-10  5:51   ` ira.weiny
     [not found]     ` <20160810055151.GB32695-W4f6Xiosr+yv7QzWx2u06xL4W9x8LtSr@public.gmane.org>
2016-08-10  8:24       ` Leon Romanovsky
2016-08-10  8:24         ` Leon Romanovsky
2016-08-10 10:17       ` Leon Romanovsky
2016-08-10 10:17         ` Leon Romanovsky
2016-08-22 18:21       ` Doug Ledford
2016-08-22 18:21         ` Doug Ledford

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