workqueue: WQ_NON_REENTRANT is meaningless and going away

Hello,

dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op but the following patches didn't remove the flag or update the documentation. Let's mark the flag deprecated and update the documentation accordingly and remove the existing usages. We can remove the flag after the next merge window.

This patchset contains the following nine patches.

0001-workqueue-mark-WQ_NON_REENTRANT-deprecated.patch 0002-dm-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch 0003-mmc-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch 0004-firewire-WQ_NON_REENTRANT-is-meaningless-and-going-a.patch 0005-dlm-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch 0006-gfs2-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch 0007-xfs-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch 0008-ceph-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch 0009-l2tp-WQ_NON_REENTRANT-is-meaningless-and-going-away.patch

0001 marks the flag deprecated. The rest remove the exising usages. This patchset as a whole doesn't introduce any behavior changes.

0001 is already applied to wq/for-3.12. The rest will be routed through the respective trees. The patches are also available in the following git branch.

git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git review-WQ_NON_REENTRANT-removal

 Documentation/workqueue.txt         |   18 ++++++------------
 drivers/firewire/core-transaction.c |    3 +--
 drivers/md/dm-crypt.c               |   10 ++--------
 drivers/md/dm-kcopyd.c              |    3 +--
 drivers/md/dm-raid1.c               |    3 +--
 drivers/md/dm.c                     |    3 +--
 drivers/mmc/host/dw_mmc.c           |    2 +-
 fs/dlm/ast.c                        |    5 +----
 fs/gfs2/main.c                      |    2 +-
 fs/xfs/xfs_super.c                  |    6 +++---
 include/linux/workqueue.h           |    7 ++++++-
 net/ceph/messenger.c                |    2 +-
 net/l2tp/l2tp_core.c                |    2 +-
 13 files changed, 26 insertions(+), 40 deletions(-)

Thanks.

--
tejun

dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op but the following patches didn't remove the flag or update the documentation. Let's mark the flag deprecated and update the documentation accordingly.

---
 Documentation/workqueue.txt | 18 ++++++------------
 include/linux/workqueue.h   |  7 ++++++-
 2 files changed, 12 insertions(+), 13 deletions(-)

index a6ab4b6..67113f6 100644
@@ -100,8 +100,8 @@ Subsystems and drivers can create and queue work items through special
 workqueue API functions as they see fit. They can influence some
 aspects of the way the work items are executed by setting flags on the
 workqueue they are putting the work item on. These flags include
-things like CPU locality, reentrancy, concurrency limits, priority and
-more.  To get a detailed overview refer to the API description of
+things like CPU locality, concurrency limits, priority and more.  To
+get a detailed overview refer to the API description of
 alloc_workqueue() below.
 
 When a work item is queued to a workqueue, the target gcwq and

@@ -166,16 +166,6 @@ resources, scheduled and executed.
 
 @flags:
 
-  WQ_NON_REENTRANT
-
-	By default, a wq guarantees non-reentrance only on the same
-	CPU.  A work item may not be executed concurrently on the same
-	CPU by multiple workers but is allowed to be executed
-	concurrently on multiple CPUs.  This flag makes sure
-	non-reentrance is enforced across all CPUs.  Work items queued
-	to a non-reentrant wq are guaranteed to be executed by at most
-	one worker system-wide at any given time.
-
   WQ_UNBOUND
 
 	Work items queued to an unbound wq are served by a special

@@ -233,6 +223,10 @@ resources, scheduled and executed.
 
 	This flag is meaningless for unbound wq.
 
+Note that the flag WQ_NON_REENTRANT no longer exists as all workqueues
+are now non-reentrant - any work item is guaranteed to be executed by
+at most one worker system-wide at any given time.
+
 @max_active:
 
 @max_active determines the maximum number of execution contexts per

index a0ed78a..594521b 100644
@@ -295,7 +295,12 @@ static inline unsigned int work_static(struct work_struct *work) { return 0; }
  * Documentation/workqueue.txt.
  */
 enum {
-	WQ_NON_REENTRANT	= 1 << 0, /* guarantee non-reentrance */
+	/*
+	 * All wqs are now non-reentrant making the following flag
+	 * meaningless.  Will be removed.
+	 */
+	WQ_NON_REENTRANT	= 1 << 0, /* DEPRECATED */
+
 	WQ_UNBOUND		= 1 << 1, /* not bound to any cpu */
 	WQ_FREEZABLE		= 1 << 2, /* freeze during suspend */
 	WQ_MEM_RECLAIM		= 1 << 3, /* may be used for memory reclaim */

1.8.3.1

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 drivers/md/dm-crypt.c  | 10 ++--------
 drivers/md/dm-kcopyd.c |  3 +--
 drivers/md/dm-raid1.c  |  3 +--
 drivers/md/dm.c        |  3 +--
 4 files changed, 5 insertions(+), 14 deletions(-)

index 6d2d41a..0fce0bc 100644
@@ -1645,20 +1645,14 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	}
 
 	ret = -ENOMEM;
-	cc->io_queue = alloc_workqueue("kcryptd_io",
-				       WQ_NON_REENTRANT|
-				       WQ_MEM_RECLAIM,
-				       1);
+	cc->io_queue = alloc_workqueue("kcryptd_io", WQ_MEM_RECLAIM, 1);
 	if (!cc->io_queue) {
 		ti->error = "Couldn't create kcryptd io queue";
 		goto bad;
 	}
 
 	cc->crypt_queue = alloc_workqueue("kcryptd",
-					  WQ_NON_REENTRANT|
-					  WQ_CPU_INTENSIVE|
-					  WQ_MEM_RECLAIM,
-					  1);
+					  WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM, 1);
 	if (!cc->crypt_queue) {
 		ti->error = "Couldn't create kcryptd queue";
 		goto bad;

index d581fe5..3a7cade 100644
@@ -833,8 +833,7 @@ struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *thro
 		goto bad_slab;
 
 	INIT_WORK(&kc->kcopyd_work, do_work);
-	kc->kcopyd_wq = alloc_workqueue("kcopyd",
-					WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
+	kc->kcopyd_wq = alloc_workqueue("kcopyd", WQ_MEM_RECLAIM, 0);
 	if (!kc->kcopyd_wq)
 		goto bad_workqueue;
 

index 699b5be..9584443 100644
@@ -1080,8 +1080,7 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->per_bio_data_size = sizeof(struct dm_raid1_bio_record);
 	ti->discard_zeroes_data_unsupported = true;
 
-	ms->kmirrord_wq = alloc_workqueue("kmirrord",
-					  WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
+	ms->kmirrord_wq = alloc_workqueue("kmirrord", WQ_MEM_RECLAIM, 0);
 	if (!ms->kmirrord_wq) {
 		DMERR("couldn't start kmirrord");
 		r = -ENOMEM;

index 9e39d2b..ef095a9 100644
@@ -1946,8 +1946,7 @@ static struct mapped_device *alloc_dev(int minor)
 	add_disk(md->disk);
 	format_dev_t(md->name, MKDEV(_major, minor));
 
-	md->wq = alloc_workqueue("kdmflush",
-				 WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
+	md->wq = alloc_workqueue("kdmflush", WQ_MEM_RECLAIM, 0);
 	if (!md->wq)
 		goto bad_thread;
 

1.8.3.1

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 drivers/mmc/host/dw_mmc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index ee5f167..b37e3c2 100644
@@ -2340,7 +2340,7 @@ int dw_mci_probe(struct dw_mci *host)
 
 	tasklet_init(&host->tasklet, dw_mci_tasklet_func, (unsigned long)host);
 	host->card_workqueue = alloc_workqueue("dw-mci-card",
-			WQ_MEM_RECLAIM | WQ_NON_REENTRANT, 1);
+					       WQ_MEM_RECLAIM, 1);
 	if (!host->card_workqueue) {
 		ret = -ENOMEM;
 		goto err_dmaunmap;

1.8.3.1

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 drivers/firewire/core-transaction.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

index 28a94c7..e5af0e3 100644
@@ -1262,8 +1262,7 @@ static int __init fw_core_init(void)
 {
 	int ret;
 
-	fw_workqueue = alloc_workqueue("firewire",
-				       WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
+	fw_workqueue = alloc_workqueue("firewire", WQ_MEM_RECLAIM, 0);
 	if (!fw_workqueue)
 		return -ENOMEM;
 

1.8.3.1

Committed to linux1394.git and pushed out to the for-next branch.

Stefan Richter
-=====-===-= -=== ====-
http://arcgraph.de/sr/

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 fs/dlm/ast.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

index 27a6ba9..0e90f0c 100644
@@ -267,10 +267,7 @@ void dlm_callback_work(struct work_struct *work)
 int dlm_callback_start(struct dlm_ls *ls)
 {
 	ls->ls_callback_wq = alloc_workqueue("dlm_callback",
-					     WQ_UNBOUND |
-					     WQ_MEM_RECLAIM |
-					     WQ_NON_REENTRANT,
-					     0);
+					     WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
 	if (!ls->ls_callback_wq) {
 		log_print("can't start dlm_callback workqueue");
 		return -ENOMEM;

1.8.3.1

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 fs/gfs2/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index e04d0e0..7b0f504 100644
@@ -155,7 +155,7 @@ static int __init init_gfs2_fs(void)
 		goto fail_wq;
 
 	gfs2_control_wq = alloc_workqueue("gfs2_control",
-			       WQ_NON_REENTRANT | WQ_UNBOUND | WQ_FREEZABLE, 0);
+					  WQ_UNBOUND | WQ_FREEZABLE, 0);
 	if (!gfs2_control_wq)
 		goto fail_recovery;
 

1.8.3.1

Hi,

Now in the GFS2 -nmw tree. Thanks,

Steve.

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 fs/xfs/xfs_super.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 1d68ffc..aeef0fc 100644
@@ -870,17 +870,17 @@ xfs_init_mount_workqueues(
 		goto out_destroy_unwritten;
 
 	mp->m_reclaim_workqueue = alloc_workqueue("xfs-reclaim/%s",
-			WQ_NON_REENTRANT, 0, mp->m_fsname);
+			0, 0, mp->m_fsname);
 	if (!mp->m_reclaim_workqueue)
 		goto out_destroy_cil;
 
 	mp->m_log_workqueue = alloc_workqueue("xfs-log/%s",
-			WQ_NON_REENTRANT, 0, mp->m_fsname);
+			0, 0, mp->m_fsname);
 	if (!mp->m_log_workqueue)
 		goto out_destroy_reclaim;
 
 	mp->m_eofblocks_workqueue = alloc_workqueue("xfs-eofblocks/%s",
-			WQ_NON_REENTRANT, 0, mp->m_fsname);
+			0, 0, mp->m_fsname);
 	if (!mp->m_eofblocks_workqueue)
 		goto out_destroy_log;
 

1.8.3.1

_______________________________________________
xfs mailing list
[email protected]
http://oss.sgi.com/mailman/listinfo/xfs

Looks good.

Applied.

_______________________________________________
xfs mailing list
[email protected]
http://oss.sgi.com/mailman/listinfo/xfs

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 net/ceph/messenger.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index eb0a46a..dd9b585 100644
@@ -290,7 +290,7 @@ int ceph_msgr_init(void)
 	if (ceph_msgr_slab_init())
 		return -ENOMEM;
 
-	ceph_msgr_wq = alloc_workqueue("ceph-msgr", WQ_NON_REENTRANT, 0);
+	ceph_msgr_wq = alloc_workqueue("ceph-msgr", 0, 0);
 	if (ceph_msgr_wq)
 		return 0;
 

1.8.3.1

Hello,

Please route this through the subsystem tree. As written in the description, this shouldn't make any functional difference and just prepares for the removal of WQ_NON_REENTRANT which is already noop.

Thanks.

------ 8< -------
dbf2576e37 ("workqueue: make all workqueues non-reentrant") made WQ_NON_REENTRANT no-op and the flag is going away. Remove its usages.

This patch doesn't introduce any behavior changes.

---
 net/l2tp/l2tp_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index feae495..07f564b 100644
@@ -1996,7 +1996,7 @@ static int __init l2tp_init(void)
 	if (rc)
 		goto out;
 
-	l2tp_wq = alloc_workqueue("l2tp", WQ_NON_REENTRANT | WQ_UNBOUND, 0);
+	l2tp_wq = alloc_workqueue("l2tp", WQ_UNBOUND, 0);
 	if (!l2tp_wq) {
 		pr_err("alloc_workqueue failed\n");
 		rc = -ENOMEM;

1.8.3.1