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>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index b8f4ec45c40a..33e24e734d50 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -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);