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Patch "IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held" has been added to the 4.7-stable tree

PATCH [email protected] 1 participant 1 message Sep 22, 2016

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Stable branch InfiniBand HFI1 driver
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This is a note to let you know that I've just added the patch titled

IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-hfi1-ib-qib-fix-qp_stats-sleep-with-rcu-read-lock-held.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From c62fb260a86dde3df5b2905432caa0e9f6898434 Mon Sep 17 00:00:00 2001

From: Mike Marciniszyn <[email protected]>
Date: Fri, 12 Aug 2016 11:17:37 -0400
Subject: IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held

From: Mike Marciniszyn <[email protected]>

commit c62fb260a86dde3df5b2905432caa0e9f6898434 upstream.

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 Ira Weiny <[email protected]>
Signed-off-by Mike Marciniszyn <[email protected]>
Reviewed-by Leon Romanovsky <[email protected]>
Signed-off-by Doug Ledford <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/infiniband/hw/hfi1/debugfs.c    |   14 +++++++++-----
 drivers/infiniband/hw/hfi1/qp.c         |    4 ----
 drivers/infiniband/hw/qib/qib_debugfs.c |   12 +++++++++---
 drivers/infiniband/hw/qib/qib_qp.c      |    4 ----
 4 files changed, 18 insertions(+), 16 deletions(-)
drivers/infiniband/hw/hfi1/debugfs.c +9 -5
@@ -223,28 +223,32 @@ 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--) {
+	do {
 		if (qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
+	} while (n--);
 
 	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 +263,7 @@ static void *_qp_stats_seq_next(struct s
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
-__releases(RCU)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
drivers/infiniband/hw/hfi1/qp.c +0 -4
@@ -595,10 +595,6 @@ struct qp_iter *qp_iter_init(struct hfi1
 
 	iter->dev = dev;
 	iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
-	if (qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }
drivers/infiniband/hw/qib/qib_debugfs.c +9 -3
@@ -189,27 +189,32 @@ static int _ctx_stats_seq_show(struct se
 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--) {
+	do {
 		if (qib_qp_iter_next(iter)) {
 			kfree(iter);
 			return NULL;
 		}
-	}
+	} while (n--);
 
 	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 +229,7 @@ static void *_qp_stats_seq_next(struct s
 }
 
 static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
+	__releases(RCU)
 {
 	rcu_read_unlock();
 }
drivers/infiniband/hw/qib/qib_qp.c +0 -4
@@ -530,10 +530,6 @@ struct qib_qp_iter *qib_qp_iter_init(str
 		return NULL;
 
 	iter->dev = dev;
-	if (qib_qp_iter_next(iter)) {
-		kfree(iter);
-		return NULL;
-	}
 
 	return iter;
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/ib-hfi1-ib-qib-fix-qp_stats-sleep-with-rcu-read-lock-held.patch