[PATCH 0/2] scsi_dh_alua fixes for kernel v4.6

[PATCH 0/2] scsi_dh_alua fixes for kernel v4.6

[Bart Van Assche]

Hello James and Martin,

Please consider the two patches in this series for inclusion in kernel 
v4.6. These patches are what I came up with while retesting the v4.6-rc1 
scsi_dh_alua handler. The actual patches are:

0001-scsi-Declare-local-symbols-static.patch
0002-scsi_dh_alua-Fix-a-recently-introduced-deadlock.patch

Thanks,

Bart.

[PATCH 1/2] Declare local symbols static

[Bart Van Assche]

Avoid that building with W=1 causes gcc to report warnings about
symbols that have not been declared.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/scsi_sysfs.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 92ffd24..2b642b1 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -81,6 +81,7 @@ const char *scsi_host_state_name(enum scsi_host_state state)
 	return name;
 }
 
+#ifdef CONFIG_SCSI_DH
 static const struct {
 	unsigned char	value;
 	char		*name;
@@ -94,7 +95,7 @@ static const struct {
 	{ SCSI_ACCESS_STATE_TRANSITIONING, "transitioning" },
 };
 
-const char *scsi_access_state_name(unsigned char state)
+static const char *scsi_access_state_name(unsigned char state)
 {
 	int i;
 	char *name = NULL;
@@ -107,6 +108,7 @@ const char *scsi_access_state_name(unsigned char state)
 	}
 	return name;
 }
+#endif
 
 static int check_set(unsigned long long *val, char *src)
 {
@@ -226,7 +228,7 @@ show_shost_state(struct device *dev, struct device_attribute *attr, char *buf)
 }
 
 /* DEVICE_ATTR(state) clashes with dev_attr_state for sdev */
-struct device_attribute dev_attr_hstate =
+static struct device_attribute dev_attr_hstate =
 	__ATTR(state, S_IRUGO | S_IWUSR, show_shost_state, store_shost_state);
 
 static ssize_t
@@ -401,7 +403,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
 	NULL
 };
 
-struct attribute_group scsi_shost_attr_group = {
+static struct attribute_group scsi_shost_attr_group = {
 	.attrs =	scsi_sysfs_shost_attrs,
 };
 
-- 
2.7.3

[PATCH 2/2] scsi_dh_alua: Fix a recently introduced deadlock

[Bart Van Assche]

While retesting the SRP initiator I ran the command "rmmod mlx4_ib"
while I/O was in progress. That command triggers SCSI device removal
indirectly. Avoid that this action triggers the following deadlock:

=================================
[ INFO: inconsistent lock state ]
4.6.0-rc0-dbg+ #2 Tainted: G           O
---------------------------------
inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
multipathd/484 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (&(&pg->lock)->rlock){+.?...}, at: [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
{IN-SOFTIRQ-W} state was registered at:
  [<ffffffff810a64a9>] __lock_acquire+0x7e9/0x1ad0
  [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
  [<ffffffff8159910e>] _raw_spin_lock_irqsave+0x3e/0x60
  [<ffffffffa04f5131>] alua_rtpg_queue+0x41/0x1d0 [scsi_dh_alua]
  [<ffffffffa04f5531>] alua_check+0xe1/0x220 [scsi_dh_alua]
  [<ffffffffa04f5709>] alua_check_sense+0x99/0xb0 [scsi_dh_alua]
  [<ffffffff813f0d01>] scsi_check_sense+0x71/0x3f0
  [<ffffffff813f2f8b>] scsi_decide_disposition+0x18b/0x1d0
  [<ffffffff813f6e52>] scsi_softirq_done+0x52/0x140
  [<ffffffff812a26f2>] blk_done_softirq+0x52/0x90
  [<ffffffff8105bc1f>] __do_softirq+0x10f/0x230
  [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
  [<ffffffff8101a675>] do_IRQ+0x65/0x110
  [<ffffffff8159a2c9>] ret_from_intr+0x0/0x19
  [<ffffffff811732f1>] kmem_cache_alloc+0x151/0x190
  [<ffffffff8118e534>] create_object+0x34/0x2d0
  [<ffffffff8158eaa6>] kmemleak_alloc_percpu+0x56/0xd0
  [<ffffffff8113ab0d>] pcpu_alloc+0x38d/0x660
  [<ffffffff8113aded>] __alloc_percpu_gfp+0xd/0x10
  [<ffffffff812e56a5>] __percpu_counter_init+0x55/0xb0
  [<ffffffff812b4989>] blkg_alloc+0x79/0x230
  [<ffffffff812b6756>] blkcg_init_queue+0x26/0x1d0
  [<ffffffff81297eed>] blk_alloc_queue_node+0x27d/0x2e0
  [<ffffffffa017766c>] dm_create+0x20c/0x570 [dm_mod]
  [<ffffffffa017e356>] dev_create+0x56/0x2c0 [dm_mod]
  [<ffffffffa017dcae>] ctl_ioctl+0x26e/0x520 [dm_mod]
  [<ffffffffa017df6e>] dm_ctl_ioctl+0xe/0x20 [dm_mod]
  [<ffffffff811aa8ee>] do_vfs_ioctl+0x8e/0x660
  [<ffffffff811aaefc>] SyS_ioctl+0x3c/0x70
  [<ffffffff81599929>] entry_SYSCALL_64_fastpath+0x1c/0xac
irq event stamp: 4290931
hardirqs last  enabled at (4290931): [ 1662.892772]
[<ffffffff81599341>] _raw_spin_unlock_irqrestore+0x31/0x50
hardirqs last disabled at (4290930): [<ffffffff815990e7>] _raw_spin_lock_irqsave+0x17/0x60
softirqs last  enabled at (4290774): [<ffffffff8105bcdb>] __do_softirq+0x1cb/0x230
softirqs last disabled at (4289831): [<ffffffff8105bec8>] irq_exit+0xa8/0xb0

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&(&pg->lock)->rlock);
  <Interrupt>
    lock(&(&pg->lock)->rlock);

 *** DEADLOCK ***

2 locks held by multipathd/484:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811d1cc3>] __blkdev_put+0x33/0x360
 #1:  (sd_ref_mutex){+.+...}, at: [<ffffffff81400afc>] scsi_disk_put+0x1c/0x40

stack backtrace:
CPU: 6 PID: 484 Comm: multipathd Tainted: G           O    4.6.0-rc0-dbg+ #2
Call Trace:
 [<ffffffff812bd115>] dump_stack+0x67/0x92
 [<ffffffff810a5175>] print_usage_bug+0x215/0x240
 [<ffffffff810a56ea>] mark_lock+0x54a/0x610
 [<ffffffff810a6505>] __lock_acquire+0x845/0x1ad0
 [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
 [<ffffffff81598f23>] _raw_spin_lock+0x33/0x50
 [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
 [<ffffffff813ff6f7>] scsi_dh_release_device+0x17/0x50
 [<ffffffff813fb8da>] scsi_device_dev_release_usercontext+0x2a/0x120
 [<ffffffff810701f0>] execute_in_process_context+0x80/0x90
 [<ffffffff813fb8a7>] scsi_device_dev_release+0x17/0x20
 [<ffffffff813c8cfd>] device_release+0x2d/0x90
 [<ffffffff812bfa8a>] kobject_release+0x7a/0x190
 [<ffffffff812bf946>] kobject_put+0x26/0x50
 [<ffffffff813c8ee2>] put_device+0x12/0x20
 [<ffffffff813edc86>] scsi_device_put+0x26/0x30
 [<ffffffff81400b0d>] scsi_disk_put+0x2d/0x40
 [<ffffffff81400b68>] sd_release+0x48/0xb0
 [<ffffffff811d1f2e>] __blkdev_put+0x29e/0x360
 [<ffffffff811d24b9>] blkdev_put+0x49/0x170
 [<ffffffff811d2600>] blkdev_close+0x20/0x30
 [<ffffffff81198f48>] __fput+0xe8/0x1f0
 [<ffffffff81199089>] ____fput+0x9/0x10
 [<ffffffff81075d9e>] task_work_run+0x6e/0xa0
 [<ffffffff81001119>] exit_to_usermode_loop+0xa9/0xb0
 [<ffffffff81001590>] syscall_return_slowpath+0xb0/0xc0
 [<ffffffff815999b7>] entry_SYSCALL_64_fastpath+0xaa/0xac

Fixes: cb0a168cb6b8 (scsi_dh_alua: update 'access_state' field)
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index a404a41..8eaed05 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -1112,9 +1112,9 @@ static void alua_bus_detach(struct scsi_device *sdev)
 	h->sdev = NULL;
 	spin_unlock(&h->pg_lock);
 	if (pg) {
-		spin_lock(&pg->lock);
+		spin_lock_irq(&pg->lock);
 		list_del_rcu(&h->node);
-		spin_unlock(&pg->lock);
+		spin_unlock_irq(&pg->lock);
 		kref_put(&pg->kref, release_port_group);
 	}
 	sdev->handler_data = NULL;
-- 
2.7.3

Re: [PATCH 2/2] scsi_dh_alua: Fix a recently introduced deadlock

[Laurence Oberman]

In similar testing last month with mlx4_ib I was able to generate the same lockup so this patch will help.
If I get a chance will add a Tested-by this week.

Reviewed-by: Laurence Oberman <loberman@redhat.com>

Laurence Oberman
Principal Software Maintenance Engineer
Red Hat Global Support Services

----- Original Message -----
From: "Bart Van Assche" <bart.vanassche@sandisk.com>
To: "James Bottomley" <james.bottomley@hansenpartnership.com>, "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "Hannes Reinecke" <hare@suse.de>, "Christoph Hellwig" <hch@infradead.org>, linux-scsi@vger.kernel.org
Sent: Monday, March 28, 2016 2:14:04 PM
Subject: [PATCH 2/2] scsi_dh_alua: Fix a recently introduced deadlock

While retesting the SRP initiator I ran the command "rmmod mlx4_ib"
while I/O was in progress. That command triggers SCSI device removal
indirectly. Avoid that this action triggers the following deadlock:

=================================
[ INFO: inconsistent lock state ]
4.6.0-rc0-dbg+ #2 Tainted: G           O
---------------------------------
inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
multipathd/484 [HC0[0]:SC0[0]:HE1:SE1] takes:
 (&(&pg->lock)->rlock){+.?...}, at: [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
{IN-SOFTIRQ-W} state was registered at:
  [<ffffffff810a64a9>] __lock_acquire+0x7e9/0x1ad0
  [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
  [<ffffffff8159910e>] _raw_spin_lock_irqsave+0x3e/0x60
  [<ffffffffa04f5131>] alua_rtpg_queue+0x41/0x1d0 [scsi_dh_alua]
  [<ffffffffa04f5531>] alua_check+0xe1/0x220 [scsi_dh_alua]
  [<ffffffffa04f5709>] alua_check_sense+0x99/0xb0 [scsi_dh_alua]
  [<ffffffff813f0d01>] scsi_check_sense+0x71/0x3f0
  [<ffffffff813f2f8b>] scsi_decide_disposition+0x18b/0x1d0
  [<ffffffff813f6e52>] scsi_softirq_done+0x52/0x140
  [<ffffffff812a26f2>] blk_done_softirq+0x52/0x90
  [<ffffffff8105bc1f>] __do_softirq+0x10f/0x230
  [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
  [<ffffffff8101a675>] do_IRQ+0x65/0x110
  [<ffffffff8159a2c9>] ret_from_intr+0x0/0x19
  [<ffffffff811732f1>] kmem_cache_alloc+0x151/0x190
  [<ffffffff8118e534>] create_object+0x34/0x2d0
  [<ffffffff8158eaa6>] kmemleak_alloc_percpu+0x56/0xd0
  [<ffffffff8113ab0d>] pcpu_alloc+0x38d/0x660
  [<ffffffff8113aded>] __alloc_percpu_gfp+0xd/0x10
  [<ffffffff812e56a5>] __percpu_counter_init+0x55/0xb0
  [<ffffffff812b4989>] blkg_alloc+0x79/0x230
  [<ffffffff812b6756>] blkcg_init_queue+0x26/0x1d0
  [<ffffffff81297eed>] blk_alloc_queue_node+0x27d/0x2e0
  [<ffffffffa017766c>] dm_create+0x20c/0x570 [dm_mod]
  [<ffffffffa017e356>] dev_create+0x56/0x2c0 [dm_mod]
  [<ffffffffa017dcae>] ctl_ioctl+0x26e/0x520 [dm_mod]
  [<ffffffffa017df6e>] dm_ctl_ioctl+0xe/0x20 [dm_mod]
  [<ffffffff811aa8ee>] do_vfs_ioctl+0x8e/0x660
  [<ffffffff811aaefc>] SyS_ioctl+0x3c/0x70
  [<ffffffff81599929>] entry_SYSCALL_64_fastpath+0x1c/0xac
irq event stamp: 4290931
hardirqs last  enabled at (4290931): [ 1662.892772]
[<ffffffff81599341>] _raw_spin_unlock_irqrestore+0x31/0x50
hardirqs last disabled at (4290930): [<ffffffff815990e7>] _raw_spin_lock_irqsave+0x17/0x60
softirqs last  enabled at (4290774): [<ffffffff8105bcdb>] __do_softirq+0x1cb/0x230
softirqs last disabled at (4289831): [<ffffffff8105bec8>] irq_exit+0xa8/0xb0

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&(&pg->lock)->rlock);
  <Interrupt>
    lock(&(&pg->lock)->rlock);

 *** DEADLOCK ***

2 locks held by multipathd/484:
 #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811d1cc3>] __blkdev_put+0x33/0x360
 #1:  (sd_ref_mutex){+.+...}, at: [<ffffffff81400afc>] scsi_disk_put+0x1c/0x40

stack backtrace:
CPU: 6 PID: 484 Comm: multipathd Tainted: G           O    4.6.0-rc0-dbg+ #2
Call Trace:
 [<ffffffff812bd115>] dump_stack+0x67/0x92
 [<ffffffff810a5175>] print_usage_bug+0x215/0x240
 [<ffffffff810a56ea>] mark_lock+0x54a/0x610
 [<ffffffff810a6505>] __lock_acquire+0x845/0x1ad0
 [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
 [<ffffffff81598f23>] _raw_spin_lock+0x33/0x50
 [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
 [<ffffffff813ff6f7>] scsi_dh_release_device+0x17/0x50
 [<ffffffff813fb8da>] scsi_device_dev_release_usercontext+0x2a/0x120
 [<ffffffff810701f0>] execute_in_process_context+0x80/0x90
 [<ffffffff813fb8a7>] scsi_device_dev_release+0x17/0x20
 [<ffffffff813c8cfd>] device_release+0x2d/0x90
 [<ffffffff812bfa8a>] kobject_release+0x7a/0x190
 [<ffffffff812bf946>] kobject_put+0x26/0x50
 [<ffffffff813c8ee2>] put_device+0x12/0x20
 [<ffffffff813edc86>] scsi_device_put+0x26/0x30
 [<ffffffff81400b0d>] scsi_disk_put+0x2d/0x40
 [<ffffffff81400b68>] sd_release+0x48/0xb0
 [<ffffffff811d1f2e>] __blkdev_put+0x29e/0x360
 [<ffffffff811d24b9>] blkdev_put+0x49/0x170
 [<ffffffff811d2600>] blkdev_close+0x20/0x30
 [<ffffffff81198f48>] __fput+0xe8/0x1f0
 [<ffffffff81199089>] ____fput+0x9/0x10
 [<ffffffff81075d9e>] task_work_run+0x6e/0xa0
 [<ffffffff81001119>] exit_to_usermode_loop+0xa9/0xb0
 [<ffffffff81001590>] syscall_return_slowpath+0xb0/0xc0
 [<ffffffff815999b7>] entry_SYSCALL_64_fastpath+0xaa/0xac

Fixes: cb0a168cb6b8 (scsi_dh_alua: update 'access_state' field)
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
index a404a41..8eaed05 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -1112,9 +1112,9 @@ static void alua_bus_detach(struct scsi_device *sdev)
 	h->sdev = NULL;
 	spin_unlock(&h->pg_lock);
 	if (pg) {
-		spin_lock(&pg->lock);
+		spin_lock_irq(&pg->lock);
 		list_del_rcu(&h->node);
-		spin_unlock(&pg->lock);
+		spin_unlock_irq(&pg->lock);
 		kref_put(&pg->kref, release_port_group);
 	}
 	sdev->handler_data = NULL;
-- 
2.7.3

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Re: [PATCH 1/2] Declare local symbols static

[Hannes Reinecke]

On 03/28/2016 08:13 PM, Bart Van Assche wrote:
> Avoid that building with W=1 causes gcc to report warnings about
> symbols that have not been declared.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Hannes Reinecke <hare@suse.de>
> ---
>  drivers/scsi/scsi_sysfs.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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Re: [PATCH 2/2] scsi_dh_alua: Fix a recently introduced deadlock

[Hannes Reinecke]

On 03/28/2016 08:14 PM, Bart Van Assche wrote:
> While retesting the SRP initiator I ran the command "rmmod mlx4_ib"
> while I/O was in progress. That command triggers SCSI device removal
> indirectly. Avoid that this action triggers the following deadlock:
> 
> =================================
> [ INFO: inconsistent lock state ]
> 4.6.0-rc0-dbg+ #2 Tainted: G           O
> ---------------------------------
> inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
> multipathd/484 [HC0[0]:SC0[0]:HE1:SE1] takes:
>  (&(&pg->lock)->rlock){+.?...}, at: [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
> {IN-SOFTIRQ-W} state was registered at:
>   [<ffffffff810a64a9>] __lock_acquire+0x7e9/0x1ad0
>   [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
>   [<ffffffff8159910e>] _raw_spin_lock_irqsave+0x3e/0x60
>   [<ffffffffa04f5131>] alua_rtpg_queue+0x41/0x1d0 [scsi_dh_alua]
>   [<ffffffffa04f5531>] alua_check+0xe1/0x220 [scsi_dh_alua]
>   [<ffffffffa04f5709>] alua_check_sense+0x99/0xb0 [scsi_dh_alua]
>   [<ffffffff813f0d01>] scsi_check_sense+0x71/0x3f0
>   [<ffffffff813f2f8b>] scsi_decide_disposition+0x18b/0x1d0
>   [<ffffffff813f6e52>] scsi_softirq_done+0x52/0x140
>   [<ffffffff812a26f2>] blk_done_softirq+0x52/0x90
>   [<ffffffff8105bc1f>] __do_softirq+0x10f/0x230
>   [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
>   [<ffffffff8101a675>] do_IRQ+0x65/0x110
>   [<ffffffff8159a2c9>] ret_from_intr+0x0/0x19
>   [<ffffffff811732f1>] kmem_cache_alloc+0x151/0x190
>   [<ffffffff8118e534>] create_object+0x34/0x2d0
>   [<ffffffff8158eaa6>] kmemleak_alloc_percpu+0x56/0xd0
>   [<ffffffff8113ab0d>] pcpu_alloc+0x38d/0x660
>   [<ffffffff8113aded>] __alloc_percpu_gfp+0xd/0x10
>   [<ffffffff812e56a5>] __percpu_counter_init+0x55/0xb0
>   [<ffffffff812b4989>] blkg_alloc+0x79/0x230
>   [<ffffffff812b6756>] blkcg_init_queue+0x26/0x1d0
>   [<ffffffff81297eed>] blk_alloc_queue_node+0x27d/0x2e0
>   [<ffffffffa017766c>] dm_create+0x20c/0x570 [dm_mod]
>   [<ffffffffa017e356>] dev_create+0x56/0x2c0 [dm_mod]
>   [<ffffffffa017dcae>] ctl_ioctl+0x26e/0x520 [dm_mod]
>   [<ffffffffa017df6e>] dm_ctl_ioctl+0xe/0x20 [dm_mod]
>   [<ffffffff811aa8ee>] do_vfs_ioctl+0x8e/0x660
>   [<ffffffff811aaefc>] SyS_ioctl+0x3c/0x70
>   [<ffffffff81599929>] entry_SYSCALL_64_fastpath+0x1c/0xac
> irq event stamp: 4290931
> hardirqs last  enabled at (4290931): [ 1662.892772]
> [<ffffffff81599341>] _raw_spin_unlock_irqrestore+0x31/0x50
> hardirqs last disabled at (4290930): [<ffffffff815990e7>] _raw_spin_lock_irqsave+0x17/0x60
> softirqs last  enabled at (4290774): [<ffffffff8105bcdb>] __do_softirq+0x1cb/0x230
> softirqs last disabled at (4289831): [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
> 
> other info that might help us debug this:
>  Possible unsafe locking scenario:
> 
>        CPU0
>        ----
>   lock(&(&pg->lock)->rlock);
>   <Interrupt>
>     lock(&(&pg->lock)->rlock);
> 
>  *** DEADLOCK ***
> 
> 2 locks held by multipathd/484:
>  #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811d1cc3>] __blkdev_put+0x33/0x360
>  #1:  (sd_ref_mutex){+.+...}, at: [<ffffffff81400afc>] scsi_disk_put+0x1c/0x40
> 
> stack backtrace:
> CPU: 6 PID: 484 Comm: multipathd Tainted: G           O    4.6.0-rc0-dbg+ #2
> Call Trace:
>  [<ffffffff812bd115>] dump_stack+0x67/0x92
>  [<ffffffff810a5175>] print_usage_bug+0x215/0x240
>  [<ffffffff810a56ea>] mark_lock+0x54a/0x610
>  [<ffffffff810a6505>] __lock_acquire+0x845/0x1ad0
>  [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
>  [<ffffffff81598f23>] _raw_spin_lock+0x33/0x50
>  [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
>  [<ffffffff813ff6f7>] scsi_dh_release_device+0x17/0x50
>  [<ffffffff813fb8da>] scsi_device_dev_release_usercontext+0x2a/0x120
>  [<ffffffff810701f0>] execute_in_process_context+0x80/0x90
>  [<ffffffff813fb8a7>] scsi_device_dev_release+0x17/0x20
>  [<ffffffff813c8cfd>] device_release+0x2d/0x90
>  [<ffffffff812bfa8a>] kobject_release+0x7a/0x190
>  [<ffffffff812bf946>] kobject_put+0x26/0x50
>  [<ffffffff813c8ee2>] put_device+0x12/0x20
>  [<ffffffff813edc86>] scsi_device_put+0x26/0x30
>  [<ffffffff81400b0d>] scsi_disk_put+0x2d/0x40
>  [<ffffffff81400b68>] sd_release+0x48/0xb0
>  [<ffffffff811d1f2e>] __blkdev_put+0x29e/0x360
>  [<ffffffff811d24b9>] blkdev_put+0x49/0x170
>  [<ffffffff811d2600>] blkdev_close+0x20/0x30
>  [<ffffffff81198f48>] __fput+0xe8/0x1f0
>  [<ffffffff81199089>] ____fput+0x9/0x10
>  [<ffffffff81075d9e>] task_work_run+0x6e/0xa0
>  [<ffffffff81001119>] exit_to_usermode_loop+0xa9/0xb0
>  [<ffffffff81001590>] syscall_return_slowpath+0xb0/0xc0
>  [<ffffffff815999b7>] entry_SYSCALL_64_fastpath+0xaa/0xac
> 
> Fixes: cb0a168cb6b8 (scsi_dh_alua: update 'access_state' field)
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> ---
>  drivers/scsi/device_handler/scsi_dh_alua.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
> index a404a41..8eaed05 100644
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -1112,9 +1112,9 @@ static void alua_bus_detach(struct scsi_device *sdev)
>  	h->sdev = NULL;
>  	spin_unlock(&h->pg_lock);
>  	if (pg) {
> -		spin_lock(&pg->lock);
> +		spin_lock_irq(&pg->lock);
>  		list_del_rcu(&h->node);
> -		spin_unlock(&pg->lock);
> +		spin_unlock_irq(&pg->lock);
>  		kref_put(&pg->kref, release_port_group);
>  	}
>  	sdev->handler_data = NULL;
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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Re: [PATCH 1/2] Declare local symbols static

[Christoph Hellwig]

On Mon, Mar 28, 2016 at 11:13:16AM -0700, Bart Van Assche wrote:
> Avoid that building with W=1 causes gcc to report warnings about
> symbols that have not been declared.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Hannes Reinecke <hare@suse.de>

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 2/2] scsi_dh_alua: Fix a recently introduced deadlock

[Christoph Hellwig]

This indeed looks like the only place where we took pg->lock without
disabling irqs.

Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 1/2] Declare local symbols static

[Ewan D. Milne]

On Mon, 2016-03-28 at 11:13 -0700, Bart Van Assche wrote:
> Avoid that building with W=1 causes gcc to report warnings about
> symbols that have not been declared.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Hannes Reinecke <hare@suse.de>
> ---
>  drivers/scsi/scsi_sysfs.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 92ffd24..2b642b1 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -81,6 +81,7 @@ const char *scsi_host_state_name(enum scsi_host_state state)
>  	return name;
>  }
>  
> +#ifdef CONFIG_SCSI_DH
>  static const struct {
>  	unsigned char	value;
>  	char		*name;
> @@ -94,7 +95,7 @@ static const struct {
>  	{ SCSI_ACCESS_STATE_TRANSITIONING, "transitioning" },
>  };
>  
> -const char *scsi_access_state_name(unsigned char state)
> +static const char *scsi_access_state_name(unsigned char state)
>  {
>  	int i;
>  	char *name = NULL;
> @@ -107,6 +108,7 @@ const char *scsi_access_state_name(unsigned char state)
>  	}
>  	return name;
>  }
> +#endif
>  
>  static int check_set(unsigned long long *val, char *src)
>  {
> @@ -226,7 +228,7 @@ show_shost_state(struct device *dev, struct device_attribute *attr, char *buf)
>  }
>  
>  /* DEVICE_ATTR(state) clashes with dev_attr_state for sdev */
> -struct device_attribute dev_attr_hstate =
> +static struct device_attribute dev_attr_hstate =
>  	__ATTR(state, S_IRUGO | S_IWUSR, show_shost_state, store_shost_state);
>  
>  static ssize_t
> @@ -401,7 +403,7 @@ static struct attribute *scsi_sysfs_shost_attrs[] = {
>  	NULL
>  };
>  
> -struct attribute_group scsi_shost_attr_group = {
> +static struct attribute_group scsi_shost_attr_group = {
>  	.attrs =	scsi_sysfs_shost_attrs,
>  };
>  

Could have been 2 patches, since the patch subject and the more
verbose description, along with the code, are really 2 separate
issues, but OK.

Reviewed-by: Ewan D. Milne <emilne@redhat.com>

Re: [PATCH 2/2] scsi_dh_alua: Fix a recently introduced deadlock

[Ewan D. Milne]

On Mon, 2016-03-28 at 11:14 -0700, Bart Van Assche wrote:
> While retesting the SRP initiator I ran the command "rmmod mlx4_ib"
> while I/O was in progress. That command triggers SCSI device removal
> indirectly. Avoid that this action triggers the following deadlock:
> 
> =================================
> [ INFO: inconsistent lock state ]
> 4.6.0-rc0-dbg+ #2 Tainted: G           O
> ---------------------------------
> inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
> multipathd/484 [HC0[0]:SC0[0]:HE1:SE1] takes:
>  (&(&pg->lock)->rlock){+.?...}, at: [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
> {IN-SOFTIRQ-W} state was registered at:
>   [<ffffffff810a64a9>] __lock_acquire+0x7e9/0x1ad0
>   [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
>   [<ffffffff8159910e>] _raw_spin_lock_irqsave+0x3e/0x60
>   [<ffffffffa04f5131>] alua_rtpg_queue+0x41/0x1d0 [scsi_dh_alua]
>   [<ffffffffa04f5531>] alua_check+0xe1/0x220 [scsi_dh_alua]
>   [<ffffffffa04f5709>] alua_check_sense+0x99/0xb0 [scsi_dh_alua]
>   [<ffffffff813f0d01>] scsi_check_sense+0x71/0x3f0
>   [<ffffffff813f2f8b>] scsi_decide_disposition+0x18b/0x1d0
>   [<ffffffff813f6e52>] scsi_softirq_done+0x52/0x140
>   [<ffffffff812a26f2>] blk_done_softirq+0x52/0x90
>   [<ffffffff8105bc1f>] __do_softirq+0x10f/0x230
>   [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
>   [<ffffffff8101a675>] do_IRQ+0x65/0x110
>   [<ffffffff8159a2c9>] ret_from_intr+0x0/0x19
>   [<ffffffff811732f1>] kmem_cache_alloc+0x151/0x190
>   [<ffffffff8118e534>] create_object+0x34/0x2d0
>   [<ffffffff8158eaa6>] kmemleak_alloc_percpu+0x56/0xd0
>   [<ffffffff8113ab0d>] pcpu_alloc+0x38d/0x660
>   [<ffffffff8113aded>] __alloc_percpu_gfp+0xd/0x10
>   [<ffffffff812e56a5>] __percpu_counter_init+0x55/0xb0
>   [<ffffffff812b4989>] blkg_alloc+0x79/0x230
>   [<ffffffff812b6756>] blkcg_init_queue+0x26/0x1d0
>   [<ffffffff81297eed>] blk_alloc_queue_node+0x27d/0x2e0
>   [<ffffffffa017766c>] dm_create+0x20c/0x570 [dm_mod]
>   [<ffffffffa017e356>] dev_create+0x56/0x2c0 [dm_mod]
>   [<ffffffffa017dcae>] ctl_ioctl+0x26e/0x520 [dm_mod]
>   [<ffffffffa017df6e>] dm_ctl_ioctl+0xe/0x20 [dm_mod]
>   [<ffffffff811aa8ee>] do_vfs_ioctl+0x8e/0x660
>   [<ffffffff811aaefc>] SyS_ioctl+0x3c/0x70
>   [<ffffffff81599929>] entry_SYSCALL_64_fastpath+0x1c/0xac
> irq event stamp: 4290931
> hardirqs last  enabled at (4290931): [ 1662.892772]
> [<ffffffff81599341>] _raw_spin_unlock_irqrestore+0x31/0x50
> hardirqs last disabled at (4290930): [<ffffffff815990e7>] _raw_spin_lock_irqsave+0x17/0x60
> softirqs last  enabled at (4290774): [<ffffffff8105bcdb>] __do_softirq+0x1cb/0x230
> softirqs last disabled at (4289831): [<ffffffff8105bec8>] irq_exit+0xa8/0xb0
> 
> other info that might help us debug this:
>  Possible unsafe locking scenario:
> 
>        CPU0
>        ----
>   lock(&(&pg->lock)->rlock);
>   <Interrupt>
>     lock(&(&pg->lock)->rlock);
> 
>  *** DEADLOCK ***
> 
> 2 locks held by multipathd/484:
>  #0:  (&bdev->bd_mutex){+.+.+.}, at: [<ffffffff811d1cc3>] __blkdev_put+0x33/0x360
>  #1:  (sd_ref_mutex){+.+...}, at: [<ffffffff81400afc>] scsi_disk_put+0x1c/0x40
> 
> stack backtrace:
> CPU: 6 PID: 484 Comm: multipathd Tainted: G           O    4.6.0-rc0-dbg+ #2
> Call Trace:
>  [<ffffffff812bd115>] dump_stack+0x67/0x92
>  [<ffffffff810a5175>] print_usage_bug+0x215/0x240
>  [<ffffffff810a56ea>] mark_lock+0x54a/0x610
>  [<ffffffff810a6505>] __lock_acquire+0x845/0x1ad0
>  [<ffffffff810a7fd0>] lock_acquire+0x60/0x80
>  [<ffffffff81598f23>] _raw_spin_lock+0x33/0x50
>  [<ffffffffa04f50a2>] alua_bus_detach+0x52/0xa0 [scsi_dh_alua]
>  [<ffffffff813ff6f7>] scsi_dh_release_device+0x17/0x50
>  [<ffffffff813fb8da>] scsi_device_dev_release_usercontext+0x2a/0x120
>  [<ffffffff810701f0>] execute_in_process_context+0x80/0x90
>  [<ffffffff813fb8a7>] scsi_device_dev_release+0x17/0x20
>  [<ffffffff813c8cfd>] device_release+0x2d/0x90
>  [<ffffffff812bfa8a>] kobject_release+0x7a/0x190
>  [<ffffffff812bf946>] kobject_put+0x26/0x50
>  [<ffffffff813c8ee2>] put_device+0x12/0x20
>  [<ffffffff813edc86>] scsi_device_put+0x26/0x30
>  [<ffffffff81400b0d>] scsi_disk_put+0x2d/0x40
>  [<ffffffff81400b68>] sd_release+0x48/0xb0
>  [<ffffffff811d1f2e>] __blkdev_put+0x29e/0x360
>  [<ffffffff811d24b9>] blkdev_put+0x49/0x170
>  [<ffffffff811d2600>] blkdev_close+0x20/0x30
>  [<ffffffff81198f48>] __fput+0xe8/0x1f0
>  [<ffffffff81199089>] ____fput+0x9/0x10
>  [<ffffffff81075d9e>] task_work_run+0x6e/0xa0
>  [<ffffffff81001119>] exit_to_usermode_loop+0xa9/0xb0
>  [<ffffffff81001590>] syscall_return_slowpath+0xb0/0xc0
>  [<ffffffff815999b7>] entry_SYSCALL_64_fastpath+0xaa/0xac
> 
> Fixes: cb0a168cb6b8 (scsi_dh_alua: update 'access_state' field)
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> ---
>  drivers/scsi/device_handler/scsi_dh_alua.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/scsi/device_handler/scsi_dh_alua.c
> index a404a41..8eaed05 100644
> --- a/drivers/scsi/device_handler/scsi_dh_alua.c
> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c
> @@ -1112,9 +1112,9 @@ static void alua_bus_detach(struct scsi_device *sdev)
>  	h->sdev = NULL;
>  	spin_unlock(&h->pg_lock);
>  	if (pg) {
> -		spin_lock(&pg->lock);
> +		spin_lock_irq(&pg->lock);
>  		list_del_rcu(&h->node);
> -		spin_unlock(&pg->lock);
> +		spin_unlock_irq(&pg->lock);
>  		kref_put(&pg->kref, release_port_group);
>  	}
>  	sdev->handler_data = NULL;

Reviewed-by: Ewan D. Milne <emilne@redhat.com>

Re: [PATCH 0/2] scsi_dh_alua fixes for kernel v4.6

[Martin K. Petersen]

>>>>> "Bart" == Bart Van Assche <bart.vanassche@sandisk.com> writes:

Bart> Please consider the two patches in this series for inclusion in
Bart> kernel v4.6. These patches are what I came up with while retesting
Bart> the v4.6-rc1 scsi_dh_alua handler. The actual patches are:

Applied to 4.6/scsi-fixes.

-- 
Martin K. Petersen	Oracle Linux Engineering