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

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 <ira.weiny@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
CC: <stable@vger.kernel.org> # 4.6.x-
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/drivers/infiniband/hw/hfi1/debugfs.c b/drivers/infiniband/hw/hfi1/debugfs.c
index dbab9d9cc288c7edb296ab25d890d3d79c93ef22..a49cc88f08a2aa6b063903fa88291c070849143e 100644 (file)
--- a/drivers/infiniband/hw/hfi1/debugfs.c
+++ b/drivers/infiniband/hw/hfi1/debugfs.c
@@ -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 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 a5aa3517e7d5c537d36786fd0d512cef6d60544c..4e4d8317c281cde45278c34104e29aca00b284f2 100644 (file)
--- 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 5e75b43c596b608adfacfeb48ea955ffa914082d..5bad8e3b40bb34517948e7a18b0497f79d4b7e16 100644 (file)
--- a/drivers/infiniband/hw/qib/qib_debugfs.c
+++ b/drivers/infiniband/hw/qib/qib_debugfs.c
@@ -189,27 +189,32 @@ 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--) {
+       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 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 9cc0aae1d78191735b31eaed33bca1ee21de7d01..f9b8cd2354d1ba6f6b077aea249f00b2f3a8e8bb 100644 (file)
--- 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;
 }