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workqueue: increase max_active of keventd and kill current_is_keventd() 

Define WQ_MAX_ACTIVE and create keventd with max_active set to half of
it which means that keventd now can process upto WQ_MAX_ACTIVE / 2 - 1
works concurrently.  Unless some combination can result in dependency
loop longer than max_active, deadlock won't happen and thus it's
unnecessary to check whether current_is_keventd() before trying to
schedule a work.  Kill current_is_keventd().

(Lockdep annotations are broken.  We need lock_map_acquire_read_norecurse())

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
This commit is contained in:
Tejun Heo 2010-06-29 10:07:14 +02:00
parent e22bee782b
commit b71ab8c202
4 changed files with 18 additions and 53 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/ia64/kernel/smpboot.c
View File

@ -519,7 +519,7 @@ do_boot_cpu (int sapicid, int cpu)
/*
* We can't use kernel_thread since we must avoid to reschedule the child.
*/
if (!keventd_up() || current_is_keventd())
if (!keventd_up())
c_idle.work.func(&c_idle.work);
else {
schedule_work(&c_idle.work);

2
arch/x86/kernel/smpboot.c
View File

@ -735,7 +735,7 @@ static int __cpuinit do_boot_cpu(int apicid, int cpu)
goto do_rest;
}
if (!keventd_up() || current_is_keventd())
if (!keventd_up())
c_idle.work.func(&c_idle.work);
else {
schedule_work(&c_idle.work);

4
include/linux/workqueue.h
View File

@ -227,6 +227,9 @@ enum {
WQ_SINGLE_CPU = 1 << 1, /* only single cpu at a time */
WQ_NON_REENTRANT = 1 << 2, /* guarantee non-reentrance */
WQ_RESCUER = 1 << 3, /* has an rescue worker */
WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
WQ_DFL_ACTIVE = WQ_MAX_ACTIVE / 2,
};
extern struct workqueue_struct *
@ -280,7 +283,6 @@ extern int schedule_delayed_work(struct delayed_work *work, unsigned long delay)
extern int schedule_delayed_work_on(int cpu, struct delayed_work *work,
unsigned long delay);
extern int schedule_on_each_cpu(work_func_t func);
extern int current_is_keventd(void);
extern int keventd_up(void);
extern void init_workqueues(void);

63
kernel/workqueue.c
View File

@ -2398,7 +2398,6 @@ EXPORT_SYMBOL(schedule_delayed_work_on);
int schedule_on_each_cpu(work_func_t func)
{
int cpu;
int orig = -1;
struct work_struct *works;
works = alloc_percpu(struct work_struct);
@ -2407,23 +2406,12 @@ int schedule_on_each_cpu(work_func_t func)
get_online_cpus();
/*
* When running in keventd don't schedule a work item on
* itself. Can just call directly because the work queue is
* already bound. This also is faster.
*/
if (current_is_keventd())
orig = raw_smp_processor_id();
for_each_online_cpu(cpu) {
struct work_struct *work = per_cpu_ptr(works, cpu);
INIT_WORK(work, func);
if (cpu != orig)
schedule_work_on(cpu, work);
schedule_work_on(cpu, work);
}
if (orig >= 0)
func(per_cpu_ptr(works, orig));
for_each_online_cpu(cpu)
flush_work(per_cpu_ptr(works, cpu));
@ -2494,41 +2482,6 @@ int keventd_up(void)
return keventd_wq != NULL;
}
int current_is_keventd(void)
{
bool found = false;
unsigned int cpu;
/*
* There no longer is one-to-one relation between worker and
* work queue and a worker task might be unbound from its cpu
* if the cpu was offlined. Match all busy workers. This
* function will go away once dynamic pool is implemented.
*/
for_each_possible_cpu(cpu) {
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker *worker;
struct hlist_node *pos;
unsigned long flags;
int i;
spin_lock_irqsave(&gcwq->lock, flags);
for_each_busy_worker(worker, i, pos, gcwq) {
if (worker->task == current) {
found = true;
break;
}
}
spin_unlock_irqrestore(&gcwq->lock, flags);
if (found)
break;
}
return found;
}
static struct cpu_workqueue_struct *alloc_cwqs(void)
{
/*
@ -2576,6 +2529,16 @@ static void free_cwqs(struct cpu_workqueue_struct *cwqs)
#endif
}
static int wq_clamp_max_active(int max_active, const char *name)
{
if (max_active < 1 || max_active > WQ_MAX_ACTIVE)
printk(KERN_WARNING "workqueue: max_active %d requested for %s "
"is out of range, clamping between %d and %d\n",
max_active, name, 1, WQ_MAX_ACTIVE);
return clamp_val(max_active, 1, WQ_MAX_ACTIVE);
}
struct workqueue_struct *__create_workqueue_key(const char *name,
unsigned int flags,
int max_active,
@ -2585,7 +2548,7 @@ struct workqueue_struct *__create_workqueue_key(const char *name,
struct workqueue_struct *wq;
unsigned int cpu;
max_active = clamp_val(max_active, 1, INT_MAX);
max_active = wq_clamp_max_active(max_active, name);
wq = kzalloc(sizeof(*wq), GFP_KERNEL);
if (!wq)
@ -3324,6 +3287,6 @@ void __init init_workqueues(void)
spin_unlock_irq(&gcwq->lock);
}
keventd_wq = create_workqueue("events");
keventd_wq = __create_workqueue("events", 0, WQ_DFL_ACTIVE);
BUG_ON(!keventd_wq);
}