This patch makes unbound worker_pools reference counted and
dynamically created and destroyed as workqueues needing them come and
go. All unbound worker_pools are hashed on unbound_pool_hash which is
keyed by the content of worker_pool->attrs.
When an unbound workqueue is allocated, get_unbound_pool() is called
with the attributes of the workqueue. If there already is a matching
worker_pool, the reference count is bumped and the pool is returned.
If not, a new worker_pool with matching attributes is created and
returned.
When an unbound workqueue is destroyed, put_unbound_pool() is called
which decrements the reference count of the associated worker_pool.
If the refcnt reaches zero, the worker_pool is destroyed in sched-RCU
safe way.
Note that the standard unbound worker_pools - normal and highpri ones
with no specific cpumask affinity - are no longer created explicitly
during init_workqueues(). init_workqueues() only initializes
workqueue_attrs to be used for standard unbound pools -
unbound_std_wq_attrs[]. The pools are spawned on demand as workqueues
are created.
v2: - Comment added to init_worker_pool() explaining that @pool should
be in a condition which can be passed to put_unbound_pool() even
on failure.
- pool->refcnt reaching zero and the pool being removed from
unbound_pool_hash should be dynamic. pool->refcnt is converted
to int from atomic_t and now manipulated inside workqueue_lock.
- Removed an incorrect sanity check on nr_idle in
put_unbound_pool() which may trigger spuriously.
All changes were suggested by Lai Jiangshan.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Introduce struct workqueue_attrs which carries worker attributes -
currently the nice level and allowed cpumask along with helper
routines alloc_workqueue_attrs() and free_workqueue_attrs().
Each worker_pool now carries ->attrs describing the attributes of its
workers. All functions dealing with cpumask and nice level of workers
are updated to follow worker_pool->attrs instead of determining them
from other characteristics of the worker_pool, and init_workqueues()
is updated to set worker_pool->attrs appropriately for all standard
pools.
Note that create_worker() is updated to always perform set_user_nice()
and use set_cpus_allowed_ptr() combined with manual assertion of
PF_THREAD_BOUND instead of kthread_bind(). This simplifies handling
random attributes without affecting the outcome.
This patch doesn't introduce any behavior changes.
v2: Missing cpumask_var_t definition caused build failure on some
archs. linux/cpumask.h included.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This will be used to implement unbound pools with custom attributes.
This patch doesn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
POOL_MANAGING_WORKERS is used to synchronize the manager role.
Synchronizing among workers doesn't need blocking and that's why it's
implemented as a flag.
It got converted to a mutex a while back to add blocking wait from CPU
hotplug path - 6037315269 ("workqueue: use mutex for global_cwq
manager exclusion"). Later it turned out that synchronization among
workers and cpu hotplug need to be done separately. Eventually,
POOL_MANAGING_WORKERS is restored and workqueue->manager_mutex got
morphed into workqueue->assoc_mutex - 552a37e936 ("workqueue: restore
POOL_MANAGING_WORKERS") and b2eb83d123 ("workqueue: rename
manager_mutex to assoc_mutex").
Now, we're gonna need to be able to lock out managers from
destroy_workqueue() to support multiple unbound pools with custom
attributes making it again necessary to be able to block on the
manager role. This patch replaces POOL_MANAGING_WORKERS with
worker_pool->manager_arb.
This patch doesn't introduce any behavior changes.
v2: s/manager_mutex/manager_arb/
Signed-off-by: Tejun Heo <tj@kernel.org>
Make worker_pool_idr protected by workqueue_lock for writes and
sched-RCU protected for reads. Lockdep assertions are added to
for_each_pool() and get_work_pool() and all their users are converted
to either hold workqueue_lock or disable preemption/irq.
worker_pool_assign_id() is updated to hold workqueue_lock when
allocating a pool ID. As idr_get_new() always performs RCU-safe
assignment, this is enough on the writer side.
As standard pools are never destroyed, there's nothing to do on that
side.
The locking is superflous at this point. This is to help
implementation of unbound pools/pwqs with custom attributes.
This patch doesn't introduce any behavior changes.
v2: Updated for_each_pwq() use if/else for the hidden assertion
statement instead of just if as suggested by Lai. This avoids
confusing the following else clause.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Make workqueue->pwqs protected by workqueue_lock for writes and
sched-RCU protected for reads. Lockdep assertions are added to
for_each_pwq() and first_pwq() and all their users are converted to
either hold workqueue_lock or disable preemption/irq.
alloc_and_link_pwqs() is updated to use list_add_tail_rcu() for
consistency which isn't strictly necessary as the workqueue isn't
visible. destroy_workqueue() isn't updated to sched-RCU release pwqs.
This is okay as the workqueue should have on users left by that point.
The locking is superflous at this point. This is to help
implementation of unbound pools/pwqs with custom attributes.
This patch doesn't introduce any behavior changes.
v2: Updated for_each_pwq() use if/else for the hidden assertion
statement instead of just if as suggested by Lai. This avoids
confusing the following else clause.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
get_pwq() takes @cpu, which can also be WORK_CPU_UNBOUND, and @wq and
returns the matching pwq (pool_workqueue). We want to move away from
using @cpu for identifying pools and pwqs for unbound pools with
custom attributes and there is only one user - workqueue_congested() -
which makes use of the WQ_UNBOUND conditional in get_pwq(). All other
users already know whether they're dealing with a per-cpu or unbound
workqueue.
Replace get_pwq() with explicit per_cpu_ptr(wq->cpu_pwqs, cpu) for
per-cpu workqueues and first_pwq() for unbound ones, and open-code
WQ_UNBOUND conditional in workqueue_congested().
Note that this makes workqueue_congested() behave sligntly differently
when @cpu other than WORK_CPU_UNBOUND is specified. It ignores @cpu
for unbound workqueues and always uses the first pwq instead of
oopsing.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
workqueue->pool_wq union is used to point either to percpu pwqs
(pool_workqueues) or single unbound pwq. As the first pwq can be
accessed via workqueue->pwqs list, there's no reason for the single
pointer anymore.
Use list_first_entry(workqueue->pwqs) to access the unbound pwq and
drop workqueue->pool_wq.single pointer and the pool_wq union. It
simplifies the code and eases implementing multiple unbound pools w/
custom attributes.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Workqueue is mixing unsigned int and int for @cpu variables. There's
no point in using unsigned int for cpus - many of cpu related APIs
take int anyway. Consistently use int for @cpu variables so that we
can use negative values to mark special ones.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Similar to how pool_workqueue iteration used to be, raising and
servicing mayday requests is based on CPU numbers. It's hairy because
cpumask_t may not be able to handle WORK_CPU_UNBOUND and cpumasks are
assumed to be always set on UP. This is ugly and can't handle
multiple unbound pools to be added for unbound workqueues w/ custom
attributes.
Add workqueue_struct->maydays. When a pool_workqueue needs rescuing,
it gets chained on the list through pool_workqueue->mayday_node and
rescuer_thread() consumes the list until it's empty.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
The three freeze/thaw related functions - freeze_workqueues_begin(),
freeze_workqueues_busy() and thaw_workqueues() - need to iterate
through all pool_workqueues of all freezable workqueues. They did it
by first iterating pools and then visiting all pwqs (pool_workqueues)
of all workqueues and process it if its pwq->pool matches the current
pool. This is rather backwards and done this way partly because
workqueue didn't have fitting iteration helpers and partly to avoid
the number of lock operations on pool->lock.
Workqueue now has fitting iterators and the locking operation overhead
isn't anything to worry about - those locks are unlikely to be
contended and the same CPU visiting the same set of locks multiple
times isn't expensive.
Restructure the three functions such that the flow better matches the
logical steps and pwq iteration is done using for_each_pwq() inside
workqueue iteration.
* freeze_workqueues_begin(): Setting of FREEZING is moved into a
separate for_each_pool() iteration. pwq iteration for clearing
max_active is updated as described above.
* freeze_workqueues_busy(): pwq iteration updated as described above.
* thaw_workqueues(): The single for_each_wq_cpu() iteration is broken
into three discrete steps - clearing FREEZING, restoring max_active,
and kicking workers. The first and last steps use for_each_pool()
and the second step uses pwq iteration described above.
This makes the code easier to understand and removes the use of
for_each_wq_cpu() for walking pwqs, which can't support multiple
unbound pwqs which will be needed to implement unbound workqueues with
custom attributes.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
With the scheduled unbound pools with custom attributes, there will be
multiple unbound pools, so it wouldn't be able to use
for_each_wq_cpu() + for_each_std_worker_pool() to iterate through all
pools.
Introduce for_each_pool() which iterates through all pools using
worker_pool_idr and use it instead of for_each_wq_cpu() +
for_each_std_worker_pool() combination in freeze_workqueues_begin().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Introduce for_each_pwq() which iterates all pool_workqueues of a
workqueue using the recently added workqueue->pwqs list and replace
for_each_pwq_cpu() usages with it.
This is primarily to remove the single unbound CPU assumption from pwq
iteration for the scheduled unbound pools with custom attributes
support which would introduce multiple unbound pwqs per workqueue;
however, it also simplifies iterator users.
Note that pwq->pool initialization is moved to alloc_and_link_pwqs()
as that now is the only place which is explicitly handling the two pwq
types.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Add workqueue_struct->pwqs list and chain all pool_workqueues
belonging to a workqueue there. This will be used to implement
generic pool_workqueue iteration and handle multiple pool_workqueues
for the scheduled unbound pools with custom attributes.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
pool_workqueues need to be aligned to 1 << WORK_STRUCT_FLAG_BITS as
the lower bits of work->data are used for flags when they're pointing
to pool_workqueues.
Due to historical reasons, unbound pool_workqueues are allocated using
kzalloc() with sufficient buffer area for alignment and aligned
manually. The original pointer is stored at the end which free_pwqs()
retrieves when freeing it.
There's no reason for this hackery anymore. Set alignment of struct
pool_workqueue to 1 << WORK_STRUCT_FLAG_BITS, add kmem_cache for
pool_workqueues with proper alignment and replace the hacky alloc and
free implementation with plain kmem_cache_zalloc/free().
In case WORK_STRUCT_FLAG_BITS gets shrunk too much and makes fields of
pool_workqueues misaligned, trigger WARN if the alignment of struct
pool_workqueue becomes smaller than that of long long.
Note that assertion on IS_ALIGNED() is removed from alloc_pwqs(). We
already have another one in pwq init loop in __alloc_workqueue_key().
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
workqueue_lock will be used to synchronize areas which require
irq-safety and there isn't much benefit in keeping it not irq-safe.
Make it irq-safe.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Workqueue has been using mostly BUG_ON()s for sanity checks, which
fail unnecessarily harshly when the assertion doesn't hold. Most
assertions can converted to be less drastic such that things can limp
along instead of dying completely. Convert BUG_ON()s to
WARN_ON[_ONCE]()s with softer failure behaviors - e.g. if assertion
check fails in destroy_worker(), trigger WARN and silently ignore
destruction request.
Most conversions are trivial. Note that sanity checks in
destroy_workqueue() are moved above removal from workqueues list so
that it can bail out without side-effects if assertion checks fail.
This patch doesn't introduce any visible behavior changes during
normal operation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Rescuers visit different worker_pools to process work items from pools
under pressure. Currently, rescuer->pool is updated outside any
locking and when an outsider looks at a rescuer, there's no way to
tell when and whether rescuer->pool is gonna change. While this
doesn't currently cause any problem, it is nasty.
With recent worker_maybe_bind_and_lock() changes, we can move
rescuer->pool updates inside pool locks such that if rescuer->pool
equals a locked pool, it's guaranteed to stay that way until the pool
is unlocked.
Move rescuer->pool inside pool->lock.
This patch doesn't introduce any visible behavior difference.
tj: Updated the description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
worker_maybe_bind_and_lock() currently takes @worker but only cares
about @worker->pool. This patch updates worker_maybe_bind_and_lock()
to take @pool instead of @worker. This will be used to better define
synchronization rules regarding rescuer->pool updates.
This doesn't introduce any functional change.
tj: Updated the comments and description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
worker_maybe_bind_and_lock() uses both @worker->task and @current at
the same time. As worker_maybe_bind_and_lock() can only be called by
the current worker task, they are always the same.
Update worker_maybe_bind_and_lock() to use %current consistently.
This doesn't introduce any functional change.
tj: Massaged the description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When a work item is off-queue, its work->data contains WORK_STRUCT_*
and WORK_OFFQ_* flags. As WORK_OFFQ_* flags are used only while a
work item is off-queue, it can occupy bits of work->data which aren't
used while off-queue. WORK_OFFQ_* currently only use bits used by
on-queue CWQ pointer. As color bits aren't used while off-queue,
there's no reason to not use them.
Lower WORK_OFFQ_FLAG_BASE from WORK_STRUCT_FLAG_BITS to
WORK_STRUCT_COLOR_SHIFT thus giving 4 more bits to off-queue flag
space which is also used to record worker_pool ID while off-queue.
This doesn't introduce any visible behavior difference.
tj: Rewrote the description.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull fbdev UAPI disintegration from David Howells:
"You'll be glad to here that the end is nigh for the UAPI patches.
Only the fbdev/framebuffer piece remains now that the SCSI stuff has
gone in.
Here are the UAPI disintegration bits for the fbdev drivers. It
appears that Florian hasn't had time to deal with my patch, but back
in December he did say he didn't mind if I pushed it forward."
Yay. No more uapi movement. And hopefully no more big header file
cleanups coming up either, it just tends to be very painful.
* tag 'disintegrate-fbdev-20121220' of git://git.infradead.org/users/dhowells/linux-headers:
UAPI: (Scripted) Disintegrate include/video
Pull Xen bug-fixes from Konrad Rzeszutek Wilk:
- Update the Xen ACPI memory and CPU hotplug locking mechanism.
- Fix PAT issues wherein various applications would not start
- Fix handling of multiple MSI as AHCI now does it.
- Fix ARM compile failures.
* tag 'stable/for-linus-3.9-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen:
xenbus: fix compile failure on ARM with Xen enabled
xen/pci: We don't do multiple MSI's.
xen/pat: Disable PAT using pat_enabled value.
xen/acpi: xen cpu hotplug minor updates
xen/acpi: xen memory hotplug minor updates
Pull more VFS bits from Al Viro:
"Unfortunately, it looks like xattr series will have to wait until the
next cycle ;-/
This pile contains 9p cleanups and fixes (races in v9fs_fid_add()
etc), fixup for nommu breakage in shmem.c, several cleanups and a bit
more file_inode() work"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
constify path_get/path_put and fs_struct.c stuff
fix nommu breakage in shmem.c
cache the value of file_inode() in struct file
9p: if v9fs_fid_lookup() gets to asking server, it'd better have hashed dentry
9p: make sure ->lookup() adds fid to the right dentry
9p: untangle ->lookup() a bit
9p: double iput() in ->lookup() if d_materialise_unique() fails
9p: v9fs_fid_add() can't fail now
v9fs: get rid of v9fs_dentry
9p: turn fid->dlist into hlist
9p: don't bother with private lock in ->d_fsdata; dentry->d_lock will do just fine
more file_inode() open-coded instances
selinux: opened file can't have NULL or negative ->f_path.dentry
(In the meantime, the hlist traversal macros have changed, so this
required a semantic conflict fixup for the newly hlistified fid->dlist)
Tejun Heo
Lai Jiangshan
Linus Torvalds