[PATCH] Workqueue Abstraction

This is the next iteration of the workqueue abstraction.

The framework includes:

 - per-CPU queueing support.

on SMP there is a per-CPU worker thread (bound to its CPU) and per-CPU
work queues - this feature is completely transparent to workqueue-users.
keventd automatically uses this feature. XFS can now update to work-queues
and have the same per-CPU performance as it had with its per-CPU worker
threads.

 - delayed work submission

there's a new queue_delayed_work(wq, work, delay) function and a new
schedule_delayed_work(work, delay) function. The later one is used to
correctly fix former tq_timer users. I've reverted those changes in 2.5.40
that changed tq_timer uses to schedule_work() - eg. in the case of
random.c or the tty flip queue it was definitely the wrong thing to do.

delayed work means a timer embedded in struct work_struct.  I considered
using split struct work_struct and delayed_work_struct types, but lots
of code actively uses task-queues in both delayed and non-delayed mode,
so i went for the more generic approach that allows both methods of work
submission.  Delayed timers do not cause any other overhead in the
normal submission path otherwise.

 - multithreaded run_workqueue() implementation

the run_workqueue() function can now be called from multiple contexts, and
a worker thread will only use up a single entryy - this property is used
by the flushing code, and can potentially be used in the future to extend
the number of per-CPU worker threads.

 - more reliable flushing

there's now a 'pending work' counter, which is used to accurately detect
when the last work-function has finished execution. It's also used to
correctly flush against timed requests. I'm not convinced whether the old
keventd implementation got this detail right.

 - i switched the arguments of the queueing function(s) per Jeff's
   suggestion, it's more straightforward this way.


Driver fixes:

i have converted almost every affected driver to the new framework. This
cleaned up tons of code. I also fixed a number of drivers that were still
using BHs (these drivers did not compile in 2.5.40).

while this means lots of changes, it might ease the QA decision whether to
put this patch into 2.5.

The pach converts roughly 80% of all tqueue-using code to workqueues - and
all the places that are not converted to workqueues yet are places that do
not compile in vanilla 2.5.40 anyway, due to unrelated changes. I've
converted a fair number of drivers that do not compile in 2.5.40, and i
think i've managed to convert every driver that compiles under 2.5.40.

6 files changed, 6 insertions, 7 deletions

diff --git a/drivers/hotplug/cpqphp.h b/drivers/hotplug/cpqphp.h
index 0be973674055..29b6b47da539 100644
--- a/drivers/hotplug/cpqphp.h
+++ b/drivers/hotplug/cpqphp.h
@@ -317,7 +317,7 @@ struct controller {
 	u16 vendor_id;
 	char proc_name[20];
 	char proc_name2[20];
-	struct tq_struct int_task_event;
+	struct work_struct int_task_event;
 	wait_queue_head_t queue;	/* sleep & wake process */
 };
 
diff --git a/drivers/hotplug/cpqphp_core.c b/drivers/hotplug/cpqphp_core.c
index 4241575713e8..3cb48d075157 100644
--- a/drivers/hotplug/cpqphp_core.c
+++ b/drivers/hotplug/cpqphp_core.c
@@ -33,7 +33,7 @@
 #include <linux/proc_fs.h>
 #include <linux/miscdevice.h>
 #include <linux/slab.h>
-#include <linux/tqueue.h>
+#include <linux/workqueue.h>
 #include <linux/pci.h>
 #include <linux/init.h>
 #include <asm/uaccess.h>
diff --git a/drivers/hotplug/cpqphp_ctrl.c b/drivers/hotplug/cpqphp_ctrl.c
index d90f7eaee445..4086fe656f3f 100644
--- a/drivers/hotplug/cpqphp_ctrl.c
+++ b/drivers/hotplug/cpqphp_ctrl.c
@@ -31,7 +31,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/slab.h>
-#include <linux/tqueue.h>
+#include <linux/workqueue.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/wait.h>
@@ -971,7 +971,6 @@ void cpqhp_ctrl_intr(int IRQ, struct controller * ctrl, struct pt_regs *regs)
 	if (schedule_flag) {
 		up(&event_semaphore);
 		dbg("Signal event_semaphore\n");
-		mark_bh(IMMEDIATE_BH);
 	}
 
 }
diff --git a/drivers/hotplug/cpqphp_nvram.c b/drivers/hotplug/cpqphp_nvram.c
index 08dca3fba90c..d8208ca574de 100644
--- a/drivers/hotplug/cpqphp_nvram.c
+++ b/drivers/hotplug/cpqphp_nvram.c
@@ -33,7 +33,7 @@
 #include <linux/proc_fs.h>
 #include <linux/miscdevice.h>
 #include <linux/slab.h>
-#include <linux/tqueue.h>
+#include <linux/workqueue.h>
 #include <linux/pci.h>
 #include <linux/init.h>
 #include <asm/uaccess.h>
diff --git a/drivers/hotplug/cpqphp_pci.c b/drivers/hotplug/cpqphp_pci.c
index 8b9b16589f3b..22baa9198815 100644
--- a/drivers/hotplug/cpqphp_pci.c
+++ b/drivers/hotplug/cpqphp_pci.c
@@ -31,7 +31,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/slab.h>
-#include <linux/tqueue.h>
+#include <linux/workqueue.h>
 #include <linux/proc_fs.h>
 #include <linux/pci.h>
 #include "cpqphp.h"
diff --git a/drivers/hotplug/cpqphp_proc.c b/drivers/hotplug/cpqphp_proc.c
index 8912f881664a..e06e929e95f1 100644
--- a/drivers/hotplug/cpqphp_proc.c
+++ b/drivers/hotplug/cpqphp_proc.c
@@ -31,7 +31,7 @@
 #include <linux/kernel.h>
 #include <linux/types.h>
 #include <linux/proc_fs.h>
-#include <linux/tqueue.h>
+#include <linux/workqueue.h>
 #include <linux/pci.h>
 #include "cpqphp.h"