Pull percpu updates from Tejun Heo:
- Major reorganization of percpu header files which I think makes
things a lot more readable and logical than before.
- percpu-refcount is updated so that it requires explicit destruction
and can be reinitialized if necessary. This was pulled into the
block tree to replace the custom percpu refcnting implemented in
blk-mq.
- In the process, percpu and percpu-refcount got cleaned up a bit
* 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (21 commits)
percpu-refcount: implement percpu_ref_reinit() and percpu_ref_is_zero()
percpu-refcount: require percpu_ref to be exited explicitly
percpu-refcount: use unsigned long for pcpu_count pointer
percpu-refcount: add helpers for ->percpu_count accesses
percpu-refcount: one bit is enough for REF_STATUS
percpu-refcount, aio: use percpu_ref_cancel_init() in ioctx_alloc()
workqueue: stronger test in process_one_work()
workqueue: clear POOL_DISASSOCIATED in rebind_workers()
percpu: Use ALIGN macro instead of hand coding alignment calculation
percpu: invoke __verify_pcpu_ptr() from the generic part of accessors and operations
percpu: preffity percpu header files
percpu: use raw_cpu_*() to define __this_cpu_*()
percpu: reorder macros in percpu header files
percpu: move {raw|this}_cpu_*() definitions to include/linux/percpu-defs.h
percpu: move generic {raw|this}_cpu_*_N() definitions to include/asm-generic/percpu.h
percpu: only allow sized arch overrides for {raw|this}_cpu_*() ops
percpu: reorganize include/linux/percpu-defs.h
percpu: move accessors from include/linux/percpu.h to percpu-defs.h
percpu: include/asm-generic/percpu.h should contain only arch-overridable parts
percpu: introduce arch_raw_cpu_ptr()
...
Pull workqueue updates from Tejun Heo:
"Lai has been doing a lot of cleanups of workqueue and kthread_work.
No significant behavior change. Just a lot of cleanups all over the
place. Some are a bit invasive but overall nothing too dangerous"
* 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
kthread_work: remove the unused wait_queue_head
kthread_work: wake up worker only when the worker is idle
workqueue: use nr_node_ids instead of wq_numa_tbl_len
workqueue: remove the misnamed out_unlock label in get_unbound_pool()
workqueue: remove the stale comment in pwq_unbound_release_workfn()
workqueue: move rescuer pool detachment to the end
workqueue: unfold start_worker() into create_worker()
workqueue: remove @wakeup from worker_set_flags()
workqueue: remove an unneeded UNBOUND test before waking up the next worker
workqueue: wake regular worker if need_more_worker() when rescuer leave the pool
workqueue: alloc struct worker on its local node
workqueue: reuse the already calculated pwq in try_to_grab_pending()
workqueue: stronger test in process_one_work()
workqueue: clear POOL_DISASSOCIATED in rebind_workers()
workqueue: sanity check pool->cpu in wq_worker_sleeping()
workqueue: clear leftover flags when detached
workqueue: remove useless WARN_ON_ONCE()
workqueue: use schedule_timeout_interruptible() instead of open code
workqueue: remove the empty check in too_many_workers()
workqueue: use "pool->cpu < 0" to stand for an unbound pool
They are the same and nr_node_ids is provided by the memory subsystem.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
After the locking was moved up to the caller of the get_unbound_pool(),
out_unlock label doesn't need to do any unlock operation and the name
became bad, so we just remove this label, and the only usage-site
"goto out_unlock" is subsituted to "return pool".
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In 75ccf5950f ("workqueue: prepare flush_workqueue() for dynamic
creation and destrucion of unbound pool_workqueues"), a comment
about the synchronization for the pwq in pwq_unbound_release_workfn()
was added. The comment claimed the flush_mutex wasn't strictly
necessary, it was correct in that time, due to the pwq was protected
by workqueue_lock.
But it is incorrect now since the wq->flush_mutex was renamed to
wq->mutex and workqueue_lock was removed, the wq->mutex is strictly
needed. But the comment was miss-updated when the synchronization
was changed.
This patch removes the incorrect comments and doesn't add any new
comment to explain why wq->mutex is needed here, which is definitely
obvious and wq->pwqs_node has "WQ" notation in its definition which is
better comment.
The old commit mentioned above also introduced a comment in link_pwq()
about the synchronization. This comment is also removed in this patch
since the whole link_pwq() is proteced by wq->mutex.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In 51697d3939 ("workqueue: use generic attach/detach routine for
rescuers"), The rescuer detaches itself from the pool before put_pwq()
so that the put_unbound_pool() will not destroy the rescuer-attached
pool.
It is unnecessary. worker_detach_from_pool() can be used as the last
statement to access to the pool just like the regular workers,
put_unbound_pool() will wait for it to detach and then free the pool.
So we move the worker_detach_from_pool() down, make it coincide with
the regular workers.
tj: Minor description update.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Simply unfold the code of start_worker() into create_worker() and
remove the original start_worker() and create_and_start_worker().
The only trade-off is the introduced overhead that the pool->lock
is released and regrabbed after the newly worker is started.
The overhead is acceptible since the manager is slow path.
And because this new locking behavior, the newly created worker
may grab the lock earlier than the manager and go to process
work items. In this case, the recheck need_to_create_worker() may be
true as expected and the manager goes to restart which is the
correct behavior.
tj: Minor updates to description and comments.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
worker_set_flags() has only two callers, each specifying %true and
%false for @wakeup. Let's push the wake up to the caller and remove
@wakeup from worker_set_flags(). The caller can use the following
instead if wakeup is necessary:
worker_set_flags();
if (need_more_worker(pool))
wake_up_worker(pool);
This makes the code simpler. This patch doesn't introduce behavior
changes.
tj: Updated description and comments.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In process_one_work():
if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool))
wake_up_worker(pool);
the first test is unneeded. Even if the first test is removed, it
doesn't affect the wake-up logic for WORKER_UNBOUND, and it will not
introduce any useless wake-ups for normal per-cpu workers since
nr_running is always >= 1. It will introduce useless/redundant
wake-ups for CPU_INTENSIVE, but this case is rare and the next patch
will also remove this redundant wake-up.
tj: Minor updates to the description and comment.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
We don't need to wake up regular worker when nr_running==1,
so need_more_worker() is sufficient here.
And need_more_worker() gives us better readability due to the name of
"keep_working()" implies the rescuer should keep working now but
the rescuer is actually leaving.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When the create_worker() is called from non-manager, the struct worker
is allocated from the node of the caller which may be different from the
node of pool->node.
So we add a node ID argument for the alloc_worker() to ensure the
struct worker is allocated from the preferable node.
tj: @nid renamed to @node for consistency.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
try_to_grab_pending() was re-calculating the associated pwq using
get_work_pwq() when it already has it cached in a local varible and
the association can't change. Reuse the local variable instead.
This doesn't introduce any functional changes.
tj: Updated description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When hot-adding and onlining CPU, kernel panic occurs, showing following
call trace.
BUG: unable to handle kernel paging request at 0000000000001d08
IP: [<ffffffff8114acfd>] __alloc_pages_nodemask+0x9d/0xb10
PGD 0
Oops: 0000 [#1] SMP
...
Call Trace:
[<ffffffff812b8745>] ? cpumask_next_and+0x35/0x50
[<ffffffff810a3283>] ? find_busiest_group+0x113/0x8f0
[<ffffffff81193bc9>] ? deactivate_slab+0x349/0x3c0
[<ffffffff811926f1>] new_slab+0x91/0x300
[<ffffffff815de95a>] __slab_alloc+0x2bb/0x482
[<ffffffff8105bc1c>] ? copy_process.part.25+0xfc/0x14c0
[<ffffffff810a3c78>] ? load_balance+0x218/0x890
[<ffffffff8101a679>] ? sched_clock+0x9/0x10
[<ffffffff81105ba9>] ? trace_clock_local+0x9/0x10
[<ffffffff81193d1c>] kmem_cache_alloc_node+0x8c/0x200
[<ffffffff8105bc1c>] copy_process.part.25+0xfc/0x14c0
[<ffffffff81114d0d>] ? trace_buffer_unlock_commit+0x4d/0x60
[<ffffffff81085a80>] ? kthread_create_on_node+0x140/0x140
[<ffffffff8105d0ec>] do_fork+0xbc/0x360
[<ffffffff8105d3b6>] kernel_thread+0x26/0x30
[<ffffffff81086652>] kthreadd+0x2c2/0x300
[<ffffffff81086390>] ? kthread_create_on_cpu+0x60/0x60
[<ffffffff815f20ec>] ret_from_fork+0x7c/0xb0
[<ffffffff81086390>] ? kthread_create_on_cpu+0x60/0x60
In my investigation, I found the root cause is wq_numa_possible_cpumask.
All entries of wq_numa_possible_cpumask is allocated by
alloc_cpumask_var_node(). And these entries are used without initializing.
So these entries have wrong value.
When hot-adding and onlining CPU, wq_update_unbound_numa() is called.
wq_update_unbound_numa() calls alloc_unbound_pwq(). And alloc_unbound_pwq()
calls get_unbound_pool(). In get_unbound_pool(), worker_pool->node is set
as follow:
3592 /* if cpumask is contained inside a NUMA node, we belong to that node */
3593 if (wq_numa_enabled) {
3594 for_each_node(node) {
3595 if (cpumask_subset(pool->attrs->cpumask,
3596 wq_numa_possible_cpumask[node])) {
3597 pool->node = node;
3598 break;
3599 }
3600 }
3601 }
But wq_numa_possible_cpumask[node] does not have correct cpumask. So, wrong
node is selected. As a result, kernel panic occurs.
By this patch, all entries of wq_numa_possible_cpumask are allocated by
zalloc_cpumask_var_node to initialize them. And the panic disappeared.
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Fixes: bce903809a ("workqueue: add wq_numa_tbl_len and wq_numa_possible_cpumask[]")
When POOL_DISASSOCIATED is cleared, the running worker's local CPU should
be the same as pool->cpu without any exception even during cpu-hotplug.
This patch changes "(proposition_A && proposition_B && proposition_C)"
to "(proposition_B && proposition_C)", so if the old compound
proposition is true, the new one must be true too. so this won't hide
any possible bug which can be hit by old test.
tj: Minor description update and dropped the obvious comment.
CC: Jason J. Herne <jjherne@linux.vnet.ibm.com>
CC: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
a9ab775bca ("workqueue: directly restore CPU affinity of workers
from CPU_ONLINE") moved pool locking into rebind_workers() but left
"pool->flags &= ~POOL_DISASSOCIATED" in workqueue_cpu_up_callback().
There is nothing necessarily wrong with it, but there is no benefit
either. Let's move it into rebind_workers() and achieve the following
benefits:
1) better readability, POOL_DISASSOCIATED is cleared in rebind_workers()
as expected.
2) we can guarantee that, when POOL_DISASSOCIATED is clear, the
running workers of the pool are on the local CPU (pool->cpu).
tj: Minor description update.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
After the recent changes, when POOL_DISASSOCIATED is cleared, the
running worker's local CPU should be the same as pool->cpu without any
exception even during cpu-hotplug. Update the sanity check in
process_one_work() accordingly.
This patch changes "(proposition_A && proposition_B && proposition_C)"
to "(proposition_B && proposition_C)", so if the old compound
proposition is true, the new one must be true too. so this will not
hide any possible bug which can be caught by the old test.
tj: Minor updates to the description.
CC: Jason J. Herne <jjherne@linux.vnet.ibm.com>
CC: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The commit a9ab775bca ("workqueue: directly restore CPU affinity of
workers from CPU_ONLINE") moved the pool->lock into rebind_workers()
without also moving "pool->flags &= ~POOL_DISASSOCIATED".
There is nothing wrong with "pool->flags &= ~POOL_DISASSOCIATED" not
being moved together, but there isn't any benefit either. We move it
into rebind_workers() and achieve these benefits:
1) Better readability. POOL_DISASSOCIATED is cleared in
rebind_workers() as expected.
2) When POOL_DISASSOCIATED is cleared, we can ensure that all the
running workers of the pool are on the local CPU (pool->cpu).
tj: Cosmetic updates to the code and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In theory, pool->cpu is equals to @cpu in wq_worker_sleeping() after
worker->flags is checked.
And "pool->cpu != cpu" sanity check will help us if something wrong.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When a worker is detached, the worker->flags may still have WORKER_UNBOUND
or WORKER_REBOUND, it is OK for all cases:
1) if it is a normal worker, the worker will be dead, it is OK.
2) if it is a rescuer, it may re-attach to a pool with this leftover flag[s],
it is still correct except it may cause unneeded wakeup.
It is correct but not good, so we just remove the leftover flags.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The @cpu is fetched via smp_processor_id() in this function,
so the check is useless.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
schedule_timeout_interruptible(CREATE_COOLDOWN) is exactly the same as
the original code.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The commit ea1abd6197 ("workqueue: reimplement idle worker rebinding")
used a trick which simply removes all to-be-bound idle workers from the
idle list and lets them add themselves back after completing rebinding.
And this trick caused the @worker_pool->nr_idle may deviate than the actual
number of idle workers on @worker_pool->idle_list. More specifically,
nr_idle may be non-zero while ->idle_list is empty. All users of
->nr_idle and ->idle_list are audited. The only affected one is
too_many_workers() which is updated to check %false if ->idle_list is
empty regardless of ->nr_idle.
The commit/trick was complicated due to it just tried to simplify an even
more complicated problem (workers had to rebind itself). But the commit
a9ab775bca ("workqueue: directly restore CPU affinity of workers
from CPU_ONLINE") fixed all these problems and the mentioned trick was
useless and is gone.
So, now the @worker_pool->nr_idle is exactly the actual number of workers
on @worker_pool->idle_list. too_many_workers() should recover as it was
before the trick. So we remove the empty check.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
There is a piece of sanity checks code in the put_unbound_pool().
The meaning of this code is "if it is not an unbound pool, it will complain
and return" IIUC. But the code uses "pool->flags & POOL_DISASSOCIATED"
imprecisely due to a non-unbound pool may also have this flags.
We should use "pool->cpu < 0" to stand for an unbound pool, so we covert the
code to it.
There is no strictly wrong if we still keep "pool->flags & POOL_DISASSOCIATED"
here, but it is just a noise if we keep it:
1) we focus on "unbound" here, not "[dis]association".
2) "pool->cpu < 0" already implies "pool->flags & POOL_DISASSOCIATED".
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull workqueue updates from Tejun Heo:
"Lai simplified worker destruction path and internal workqueue locking
and there are some other minor changes.
Except for the removal of some long-deprecated interfaces which
haven't had any in-kernel user for quite a while, there shouldn't be
any difference to workqueue users"
* 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
kernel/workqueue.c: pr_warning/pr_warn & printk/pr_info
workqueue: remove the confusing POOL_FREEZING
workqueue: rename first_worker() to first_idle_worker()
workqueue: remove unused work_clear_pending()
workqueue: remove unused WORK_CPU_END
workqueue: declare system_highpri_wq
workqueue: use generic attach/detach routine for rescuers
workqueue: separate pool-attaching code out from create_worker()
workqueue: rename manager_mutex to attach_mutex
workqueue: narrow the protection range of manager_mutex
workqueue: convert worker_idr to worker_ida
workqueue: separate iteration role from worker_idr
workqueue: destroy worker directly in the idle timeout handler
workqueue: async worker destruction
workqueue: destroy_worker() should destroy idle workers only
workqueue: use manager lock only to protect worker_idr
workqueue: Remove deprecated system_nrt[_freezable]_wq
workqueue: Remove deprecated flush[_delayed]_work_sync()
kernel/workqueue.c: pr_warning/pr_warn & printk/pr_info
workqueue: simplify wq_update_unbound_numa() by jumping to use_dfl_pwq if the target cpumask equals wq's
