[libsas PATCH v15] scsi, sd: limit the scope of the async probe domain

[libsas PATCH v15] scsi, sd: limit the scope of the async probe domain

[Dan Williams]

sd injects and synchronizes probe work on the global kernel-wide domain.
This runs into conflict with PM that wants to perform resume actions in
async context:

[  494.237079] INFO: task kworker/u:3:554 blocked for more than 120 seconds.
[  494.294396] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  494.360809] kworker/u:3     D 0000000000000000     0   554      2 0x00000000
[  494.420739]  ffff88012e4d3af0 0000000000000046 ffff88013200c160 ffff88012e4d3fd8
[  494.484392]  ffff88012e4d3fd8 0000000000012500 ffff8801394ea0b0 ffff88013200c160
[  494.548038]  ffff88012e4d3ae0 00000000000001e3 ffffffff81a249e0 ffff8801321c5398
[  494.611685] Call Trace:
[  494.632649]  [<ffffffff8149dd25>] schedule+0x5a/0x5c
[  494.674687]  [<ffffffff8104b968>] async_synchronize_cookie_domain+0xb6/0x112
[  494.734177]  [<ffffffff810461ff>] ? __init_waitqueue_head+0x50/0x50
[  494.787134]  [<ffffffff8131a224>] ? scsi_remove_target+0x48/0x48
[  494.837900]  [<ffffffff8104b9d9>] async_synchronize_cookie+0x15/0x17
[  494.891567]  [<ffffffff8104ba49>] async_synchronize_full+0x54/0x70  <-- here we wait for async contexts to complete
[  494.943783]  [<ffffffff8104b9f5>] ? async_synchronize_full_domain+0x1a/0x1a
[  495.002547]  [<ffffffffa00114b1>] sd_remove+0x2c/0xa2 [sd_mod]
[  495.051861]  [<ffffffff812fe94f>] __device_release_driver+0x86/0xcf
[  495.104807]  [<ffffffff812fe9bd>] device_release_driver+0x25/0x32  <-- here we take device_lock()

[  853.511341] INFO: task kworker/u:4:549 blocked for more than 120 seconds.
[  853.568693] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  853.635119] kworker/u:4     D ffff88013097b5d0     0   549      2 0x00000000
[  853.695129]  ffff880132773c40 0000000000000046 ffff880130790000 ffff880132773fd8
[  853.758990]  ffff880132773fd8 0000000000012500 ffff88013288a0b0 ffff880130790000
[  853.822796]  0000000000000246 0000000000000040 ffff88013097b5c8 ffff880130790000
[  853.886633] Call Trace:
[  853.907631]  [<ffffffff8149dd25>] schedule+0x5a/0x5c
[  853.949670]  [<ffffffff8149cc44>] __mutex_lock_common+0x220/0x351
[  854.001225]  [<ffffffff81304bd7>] ? device_resume+0x58/0x1c4
[  854.049082]  [<ffffffff81304bd7>] ? device_resume+0x58/0x1c4
[  854.097011]  [<ffffffff8149ce48>] mutex_lock_nested+0x2f/0x36   <-- here we wait for device_lock()
[  854.145591]  [<ffffffff81304bd7>] device_resume+0x58/0x1c4
[  854.192066]  [<ffffffff81304d61>] async_resume+0x1e/0x45
[  854.237019]  [<ffffffff8104bc93>] async_run_entry_fn+0xc6/0x173  <-- ...while running in async context

Provide a 'scsi_sd_probe_domain' so that async probe actions actions can
be flushed without regard for the state of PM, and allow for the resume
path to handle devices that have transitioned from SDEV_QUIESCE to
SDEV_DEL prior to resume.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
[alan: uplevel scsi_sd_probe_domain, clarify scsi_device_resume]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---

 Changes since v14: http://marc.info/?l=linux-scsi&m=133252249201847&w=2

 linux-next reports:
 In file included from drivers/scsi/hosts.c:41:0:
 drivers/scsi/scsi_priv.h:166:1: warning: "__enabled_CONFIG_PM" is not defined [-Wundef]
 drivers/scsi/scsi_priv.h:166:1: warning: "__enabled_CONFIG_PM_MODULE" is not defined [-Wundef]

 ...so just drop IS_ENABLED() and unconditionally provide
scsi_sd_probe_domain as a part of the scsi core.  This version of the
topic also drops the sysfs change since Greg asked the printk change to
be separated from the crash workaround.


 drivers/scsi/scsi.c      |    4 ++++
 drivers/scsi/scsi_lib.c  |   10 +++++++---
 drivers/scsi/scsi_pm.c   |    2 +-
 drivers/scsi/scsi_priv.h |    2 ++
 drivers/scsi/sd.c        |    5 +++--
 5 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 07322ec..2ecdb01 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -90,6 +90,10 @@ unsigned int scsi_logging_level;
 EXPORT_SYMBOL(scsi_logging_level);
 #endif
 
+/* sd and scsi_pm need to coordinate flushing async actions */
+LIST_HEAD(scsi_sd_probe_domain);
+EXPORT_SYMBOL(scsi_sd_probe_domain);
+
 /* NB: These are exposed through /proc/scsi/scsi and form part of the ABI.
  * You may not alter any existing entry (although adding new ones is
  * encouraged once assigned by ANSI/INCITS T10
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index b4833de..992ff63 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2348,10 +2348,14 @@ EXPORT_SYMBOL(scsi_device_quiesce);
  *
  *	Must be called with user context, may sleep.
  */
-void
-scsi_device_resume(struct scsi_device *sdev)
+void scsi_device_resume(struct scsi_device *sdev)
 {
-	if(scsi_device_set_state(sdev, SDEV_RUNNING))
+	/* check if the device state was mutated prior to resume, and if
+	 * so assume the state is being managed elsewhere (for example
+	 * device deleted during suspend)
+	 */
+	if (sdev->sdev_state != SDEV_QUIESCE ||
+	    scsi_device_set_state(sdev, SDEV_RUNNING))
 		return;
 	scsi_run_queue(sdev->request_queue);
 }
diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
index c467064..f661a41 100644
--- a/drivers/scsi/scsi_pm.c
+++ b/drivers/scsi/scsi_pm.c
@@ -97,7 +97,7 @@ static int scsi_bus_prepare(struct device *dev)
 {
 	if (scsi_is_sdev_device(dev)) {
 		/* sd probing uses async_schedule.  Wait until it finishes. */
-		async_synchronize_full();
+		async_synchronize_full_domain(&scsi_sd_probe_domain);
 
 	} else if (scsi_is_host_device(dev)) {
 		/* Wait until async scanning is finished */
diff --git a/drivers/scsi/scsi_priv.h b/drivers/scsi/scsi_priv.h
index be4fa6d..07ce3f5 100644
--- a/drivers/scsi/scsi_priv.h
+++ b/drivers/scsi/scsi_priv.h
@@ -163,6 +163,8 @@ static inline int scsi_autopm_get_host(struct Scsi_Host *h) { return 0; }
 static inline void scsi_autopm_put_host(struct Scsi_Host *h) {}
 #endif /* CONFIG_PM_RUNTIME */
 
+extern struct list_head scsi_sd_probe_domain;
+
 /* 
  * internal scsi timeout functions: for use by mid-layer and transport
  * classes.
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index bd17cf8..19e27d8 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -65,6 +65,7 @@
 #include <scsi/scsicam.h>
 
 #include "sd.h"
+#include "scsi_priv.h"
 #include "scsi_logging.h"
 
 MODULE_AUTHOR("Eric Youngdale");
@@ -2717,7 +2718,7 @@ static int sd_probe(struct device *dev)
 	dev_set_drvdata(dev, sdkp);
 
 	get_device(&sdkp->dev);	/* prevent release before async_schedule */
-	async_schedule(sd_probe_async, sdkp);
+	async_schedule_domain(sd_probe_async, sdkp, &scsi_sd_probe_domain);
 
 	return 0;
 
@@ -2751,7 +2752,7 @@ static int sd_remove(struct device *dev)
 	sdkp = dev_get_drvdata(dev);
 	scsi_autopm_get_device(sdkp->device);
 
-	async_synchronize_full();
+	async_synchronize_full_domain(&scsi_sd_probe_domain);
 	blk_queue_prep_rq(sdkp->device->request_queue, scsi_prep_fn);
 	blk_queue_unprep_rq(sdkp->device->request_queue, NULL);
 	device_del(&sdkp->dev);