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Date:	Sat, 8 Mar 2014 10:26:10 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Lai Jiangshan <laijs@...fujitsu.com>,
	Stefan Richter <stefanr@...6.in-berlin.de>
Subject: [GIT PULL] workqueue fixes for v3.14-rc5

Hello, Linus.

This pull request contains a workqueue usage fix for firewire.  For
quite a long time now, workqueue only treats two work items identical
iff both their addresses and callbacks match.  This is to avoid
introducing false dependency through the work item being recycled
while being executed.  This changes non-reentrancy guarantee for the
users of PREPARE[_DELAYED]_WORK() - if the function changes,
reentrancy isn't guaranteed against the previous instance.  Firewire
depended on such nonreentrancy guarantee.  This is fixed by doing the
work item multiplexing from firewire proper while keeping the work
function unchanged.

The following changes since commit 5bdfff96c69a4d5ab9c49e60abf9e070ecd2acbb:

  workqueue: ensure @task is valid across kthread_stop() (2014-02-18 16:35:20 -0500)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-3.14-fixes

for you to fetch changes up to 70044d71d31d6973665ced5be04ef39ac1c09a48:

  firewire: don't use PREPARE_DELAYED_WORK (2014-03-07 10:19:57 -0500)

Thanks.

----------------------------------------------------------------
Tejun Heo (1):
      firewire: don't use PREPARE_DELAYED_WORK

 drivers/firewire/core-device.c | 22 +++++++++++++++-------
 drivers/firewire/sbp2.c        | 17 +++++++++++++----
 include/linux/firewire.h       |  1 +
 3 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/drivers/firewire/core-device.c b/drivers/firewire/core-device.c
index de4aa40..2c6d5e1 100644
--- a/drivers/firewire/core-device.c
+++ b/drivers/firewire/core-device.c
@@ -916,7 +916,7 @@ static int lookup_existing_device(struct device *dev, void *data)
 		old->config_rom_retries = 0;
 		fw_notice(card, "rediscovered device %s\n", dev_name(dev));
 
-		PREPARE_DELAYED_WORK(&old->work, fw_device_update);
+		old->workfn = fw_device_update;
 		fw_schedule_device_work(old, 0);
 
 		if (current_node == card->root_node)
@@ -1075,7 +1075,7 @@ static void fw_device_init(struct work_struct *work)
 	if (atomic_cmpxchg(&device->state,
 			   FW_DEVICE_INITIALIZING,
 			   FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
-		PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
+		device->workfn = fw_device_shutdown;
 		fw_schedule_device_work(device, SHUTDOWN_DELAY);
 	} else {
 		fw_notice(card, "created device %s: GUID %08x%08x, S%d00\n",
@@ -1196,13 +1196,20 @@ static void fw_device_refresh(struct work_struct *work)
 		  dev_name(&device->device), fw_rcode_string(ret));
  gone:
 	atomic_set(&device->state, FW_DEVICE_GONE);
-	PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
+	device->workfn = fw_device_shutdown;
 	fw_schedule_device_work(device, SHUTDOWN_DELAY);
  out:
 	if (node_id == card->root_node->node_id)
 		fw_schedule_bm_work(card, 0);
 }
 
+static void fw_device_workfn(struct work_struct *work)
+{
+	struct fw_device *device = container_of(to_delayed_work(work),
+						struct fw_device, work);
+	device->workfn(work);
+}
+
 void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 {
 	struct fw_device *device;
@@ -1252,7 +1259,8 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 		 * power-up after getting plugged in.  We schedule the
 		 * first config rom scan half a second after bus reset.
 		 */
-		INIT_DELAYED_WORK(&device->work, fw_device_init);
+		device->workfn = fw_device_init;
+		INIT_DELAYED_WORK(&device->work, fw_device_workfn);
 		fw_schedule_device_work(device, INITIAL_DELAY);
 		break;
 
@@ -1268,7 +1276,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 		if (atomic_cmpxchg(&device->state,
 			    FW_DEVICE_RUNNING,
 			    FW_DEVICE_INITIALIZING) == FW_DEVICE_RUNNING) {
-			PREPARE_DELAYED_WORK(&device->work, fw_device_refresh);
+			device->workfn = fw_device_refresh;
 			fw_schedule_device_work(device,
 				device->is_local ? 0 : INITIAL_DELAY);
 		}
@@ -1283,7 +1291,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 		smp_wmb();  /* update node_id before generation */
 		device->generation = card->generation;
 		if (atomic_read(&device->state) == FW_DEVICE_RUNNING) {
-			PREPARE_DELAYED_WORK(&device->work, fw_device_update);
+			device->workfn = fw_device_update;
 			fw_schedule_device_work(device, 0);
 		}
 		break;
@@ -1308,7 +1316,7 @@ void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
 		device = node->data;
 		if (atomic_xchg(&device->state,
 				FW_DEVICE_GONE) == FW_DEVICE_RUNNING) {
-			PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
+			device->workfn = fw_device_shutdown;
 			fw_schedule_device_work(device,
 				list_empty(&card->link) ? 0 : SHUTDOWN_DELAY);
 		}
diff --git a/drivers/firewire/sbp2.c b/drivers/firewire/sbp2.c
index 281029d..7aef911 100644
--- a/drivers/firewire/sbp2.c
+++ b/drivers/firewire/sbp2.c
@@ -146,6 +146,7 @@ struct sbp2_logical_unit {
 	 */
 	int generation;
 	int retries;
+	work_func_t workfn;
 	struct delayed_work work;
 	bool has_sdev;
 	bool blocked;
@@ -864,7 +865,7 @@ static void sbp2_login(struct work_struct *work)
 	/* set appropriate retry limit(s) in BUSY_TIMEOUT register */
 	sbp2_set_busy_timeout(lu);
 
-	PREPARE_DELAYED_WORK(&lu->work, sbp2_reconnect);
+	lu->workfn = sbp2_reconnect;
 	sbp2_agent_reset(lu);
 
 	/* This was a re-login. */
@@ -918,7 +919,7 @@ static void sbp2_login(struct work_struct *work)
 	 * If a bus reset happened, sbp2_update will have requeued
 	 * lu->work already.  Reset the work from reconnect to login.
 	 */
-	PREPARE_DELAYED_WORK(&lu->work, sbp2_login);
+	lu->workfn = sbp2_login;
 }
 
 static void sbp2_reconnect(struct work_struct *work)
@@ -952,7 +953,7 @@ static void sbp2_reconnect(struct work_struct *work)
 		    lu->retries++ >= 5) {
 			dev_err(tgt_dev(tgt), "failed to reconnect\n");
 			lu->retries = 0;
-			PREPARE_DELAYED_WORK(&lu->work, sbp2_login);
+			lu->workfn = sbp2_login;
 		}
 		sbp2_queue_work(lu, DIV_ROUND_UP(HZ, 5));
 
@@ -972,6 +973,13 @@ static void sbp2_reconnect(struct work_struct *work)
 	sbp2_conditionally_unblock(lu);
 }
 
+static void sbp2_lu_workfn(struct work_struct *work)
+{
+	struct sbp2_logical_unit *lu = container_of(to_delayed_work(work),
+						struct sbp2_logical_unit, work);
+	lu->workfn(work);
+}
+
 static int sbp2_add_logical_unit(struct sbp2_target *tgt, int lun_entry)
 {
 	struct sbp2_logical_unit *lu;
@@ -998,7 +1006,8 @@ static int sbp2_add_logical_unit(struct sbp2_target *tgt, int lun_entry)
 	lu->blocked  = false;
 	++tgt->dont_block;
 	INIT_LIST_HEAD(&lu->orb_list);
-	INIT_DELAYED_WORK(&lu->work, sbp2_login);
+	lu->workfn = sbp2_login;
+	INIT_DELAYED_WORK(&lu->work, sbp2_lu_workfn);
 
 	list_add_tail(&lu->link, &tgt->lu_list);
 	return 0;
diff --git a/include/linux/firewire.h b/include/linux/firewire.h
index 5d7782e..c3683bd 100644
--- a/include/linux/firewire.h
+++ b/include/linux/firewire.h
@@ -200,6 +200,7 @@ struct fw_device {
 	unsigned irmc:1;
 	unsigned bc_implemented:2;
 
+	work_func_t workfn;
 	struct delayed_work work;
 	struct fw_attribute_group attribute_group;
 };
--
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