evie/android_kernel_oneplus_msm8998
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Merge branch 'for-linus' of git://git.kernel.dk/linux-block

Browse source 
Pull one last block fix from Jens Axboe:
 "We've had an issue with scsi-mq where probing takes forever.  This was
  bisected down to the percpu changes for blk_mq_queue_enter(), and the
  fact we now suffer an RCU grace period when killing a queue.  SCSI
  creates and destroys tons of queues, so this let to 10s of seconds of
  stalls at boot for some.

  Tejun has a real fix for this, but it's too involved for 3.17.  So
  this is a temporary workaround to expedite the queue killing until we
  can fold in the real fix for 3.18 when that merge window opens"

* 'for-linus' of git://git.kernel.dk/linux-block:
  blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe
This commit is contained in:
Linus Torvalds 2014-09-24 09:51:50 -07:00
commit 02f130a787
3 changed files with 27 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

11
block/blk-mq.c
View file

@ -119,7 +119,16 @@ void blk_mq_freeze_queue(struct request_queue *q)
spin_unlock_irq(q->queue_lock);
if (freeze) {
percpu_ref_kill(&q->mq_usage_counter);
/*
* XXX: Temporary kludge to work around SCSI blk-mq stall.
* SCSI synchronously creates and destroys many queues
* back-to-back during probe leading to lengthy stalls.
* This will be fixed by keeping ->mq_usage_counter in
* atomic mode until genhd registration, but, for now,
* let's work around using expedited synchronization.
*/
__percpu_ref_kill_expedited(&q->mq_usage_counter);
blk_mq_run_queues(q, false);
}
wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->mq_usage_counter));

1
include/linux/percpu-refcount.h
View file

@ -71,6 +71,7 @@ void percpu_ref_reinit(struct percpu_ref *ref);
void percpu_ref_exit(struct percpu_ref *ref);
void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
percpu_ref_func_t *confirm_kill);
void __percpu_ref_kill_expedited(struct percpu_ref *ref);
/**
* percpu_ref_kill - drop the initial ref

16
lib/percpu-refcount.c
View file

@ -184,3 +184,19 @@ void percpu_ref_kill_and_confirm(struct percpu_ref *ref,
call_rcu_sched(&ref->rcu, percpu_ref_kill_rcu);
}
EXPORT_SYMBOL_GPL(percpu_ref_kill_and_confirm);
/*
* XXX: Temporary kludge to work around SCSI blk-mq stall. Used only by
* block/blk-mq.c::blk_mq_freeze_queue(). Will be removed during v3.18
* devel cycle. Do not use anywhere else.
*/
void __percpu_ref_kill_expedited(struct percpu_ref *ref)
{
WARN_ONCE(ref->pcpu_count_ptr & PCPU_REF_DEAD,
"percpu_ref_kill() called more than once on %pf!",
ref->release);
ref->pcpu_count_ptr |= PCPU_REF_DEAD;
synchronize_sched_expedited();
percpu_ref_kill_rcu(&ref->rcu);
}