As part of interface combination checking, verify any new
interface's beacon intervals. In fact, just always add the
beacon interval since that's harmless.

With this patch, mac80211 is prepared for drivers that set
the min_beacon_int_gcd parameter in interface combinations.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Remove the pointless checking against interface combinations in
the initial basic beacon interval validation, that currently isn't
taking into account radar detection or channels properly. Instead,
just validate the basic range there, and then delay real checking
to the interface combination validation that drivers must do.

This means that drivers wanting to use the beacon_int_min_gcd will
now have to pass the new_beacon_int when validating the AP/mesh
start.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

This can't really be supported right now, because the IBSS
interface may change its beacon interval at any time due to
joining another network; thus, there's already "support"
for different beacon intervals here, implicitly.

Until we figure out how we should handle this case (continue
to allow it to arbitrarily join? Join only if compatible?)
disallow advertising that different beacon intervals are
supported if IBSS is allowed.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

This is needed for beacon interval validation; if we don't
store it, then new interfaces added won't validate that the
beacon interval is the same as existing ones. Fix this.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

We shouldn't abort the iteration with an error when one of the
potential combinations can't accomodate the beacon interval
request, we should just skip that particular combination. Fix
the code to do so.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Add a helper using wdev to check if interface is running. This
deals with both non-netdev and netdev interfaces. In struct
wireless_dev replace 'p2p_started' and 'nan_started' by
'is_running' as those are mutually exclusive anyway, and unify
all the code to use wdev_running().
Signed-off-by: NArend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

The old WDS 4-addr frame support is very limited, e.g.
 * no encryption is possible on such links
 * it cannot support rate/HT/VHT negotiation
 * management APIs are very restricted

These make the WDS legacy mode useless in practice.

All of these are resolved by the 4-addr AP/client support,
so there's also no reason to improve WDS in the future.

Therefore, add a Kconfig option to disable legacy WDS.
This gives people an "emergency valve" while they migrate
to the better-supported 4-addr AP/client option; we plan
to remove it (and the associated cfg80211/mac80211 code,
which is the ultimate goal) in the future.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Allow vendor commands that require WIPHY_VENDOR_CMD_NEED_RUNNING flag
to be sent to NAN interface.
Signed-off-by: NAndrei Otcheretianski <andrei.otcheretianski@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

On a disconnect request from userspace, cfg80211 currently calls
called rdev_disconnect() only in case that 'current_bss' was set,
i.e. connection had been established.

Change this to allow the userspace call to succeed and call the
driver's disconnect() method also while the connection attempt is
in progress, to be able to abort attempts.
Signed-off-by: NIlan Peer <ilan.peer@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
[change commit subject/message]
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

The uapsd_queue field is in QoS IE order and not in
IEEE80211_AC_*'s order.
This means that mac80211 would get confused between
BK and BE which is certainly not such a big deal but
needs to be fixed.
Signed-off-by: NEmmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Currently mac80211 determines whether HW does fragmentation
by checking whether the set_frag_threshold callback is set
or not.
However, some drivers may want to set the HW fragmentation
capability depending on HW generation.
Allow this by checking a HW flag instead of checking the
callback.
Signed-off-by: NSara Sharon <sara.sharon@intel.com>
[added the flag to ath10k and wlcore]
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

iwlwifi will check internally that the tid maps to an AC
that is trigger enabled, but can't know what tid exactly.
Allow the driver to pass a generic tid and make mac80211
assume that a trigger frame was received.
Signed-off-by: NEmmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

When the driver sets the SUPPORTS_REORDERING_BUFFER hardware flag,
the debugfs data for RX aggregation sessions won't even indicate
that a session is open. Since the previous fix to store the dialog
token separately, we can indicate that it's open and add the token
so that there's at least some data (ssn is not available.)
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

On drivers setting the SUPPORTS_REORDERING_BUFFER hardware flag,
we crash when the peer sends an AddBA request while we already
have a session open on the seame TID; this is because on those
drivers, the tid_agg_rx is left NULL even though the session is
valid, and the agg_session_valid bit is set.

To fix this, store the dialog tokens outside the tid_agg_rx to
be able to compare them to the received AddBA request.

Fixes: f89e07d4 ("mac80211: agg-rx: refuse ADDBA Request with timeout update")
Reported-by: NEmmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

The values don't match the radiotap spec, corrected that.
Reported-by: NOz Shalev <oz.shalev@intel.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

'limits' is malloced in cfg80211_iter_combinations() and should be freed
before leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: 0c317a02 ("cfg80211: support virtual interfaces with different beacon intervals")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

According to IEEE 802.11-2012 section 8.3.2 table 8-19, the outer SA/DA
of A-MSDU frames need to be changed depending on FromDS/ToDS values.
Signed-off-by: NMichael Braun <michael-dev@fami-braun.de>
[use ether_addr_copy and add alignment annotations]
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Signed-off-by: NMichael Braun <michael-dev@fami-braun.de>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

For mac80211_hwsim interfaces, suggest to use wpa_supplicant with the more
modern, netlink based driver instead of wext.
Signed-off-by: NLinus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

To avoid unused variable warnings when CONFIG_PM isn't set,
add the appropriate ifdef to the policies that are only used
for WoWLAN, which can only be invoked when CONFIG_PM is set.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

This was clearly intended to be used in the attribute parsing,
so do that instead of leaving the attribute policy unused.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

This commit provides a mechanism for the host drivers to advertise the
support for different beacon intervals among the respective interface
combinations in a group, through NL80211_IFACE_COMB_BI_MIN_GCD (u32).

This value will be compared against GCD of all beaconing interfaces of
matching combinations.

If the driver doesn't advertise this value, the old behaviour where
all beacon intervals must be identical is retained.

If it is specified, then any beacon interval for an interface in the
interface combination as well as the GCD of all active beacon intervals
in the combination must be greater or equal to this value.
Signed-off-by: NPurushottam Kushwaha <pkushwah@qti.qualcomm.com>
[change commit message, some variable names, small other things]
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Move the growing parameter list to a structure for the interface
combination check and iteration functions in cfg80211 and mac80211
to make the code easier to understand.
Signed-off-by: NPurushottam Kushwaha <pkushwah@qti.qualcomm.com>
[edit commit message]
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Michael Braun reported that when trying to inject A-MSDUs over
monitor interfaces, the frame doesn't come out right since the
QoS header A-MSDU bit is overwritten.

Rather than adding that bit specifically simply preserve those
bits that we don't set here, since we typically get here with
a zeroed-out QoS header anyway.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

This patch adds filtering for multicast data packets on AP_VLAN
interfaces that have no authorized station connected and changes
filtering on AP interfaces to not count stations assigned to
AP_VLAN interfaces.

This saves airtime and avoids waking up other stations currently
authorized in this BSS. When using WPA, the packets dropped could
not be decrypted by any station.

The behaviour when there are no AP_VLAN interfaces is left unchanged.

When there are AP_VLAN interfaces, this patch
1. adds filtering multicast data packets sent on AP_VLAN interfaces
   that have no authorized station connected.
   No filtering happens on 4addr AP_VLAN interfaces.
2. makes filtering of multicast data packets sent on AP interfaces
   depend on the number of authorized stations in this bss not
   assigned to an AP_VLAN interface.

Therefore, a new num_mcast_sta counter is added for AP_VLAN interfaces.
The existing one for AP interfaces is altered to not track stations
assigned to an AP_VLAN interface.

The new counter is exposed in debugfs.
Signed-off-by: NMichael Braun <michael-dev@fami-braun.de>
[reformat commit message a bit, unline ieee80211_vif_{inc,dec}_num_mcast]
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Checking for num_mcast_sta in __ieee80211_request_smps_ap() is
unnecessary as sta list will be empty in this case anyway, so
the list iteration will just exit immediately. Since this isn't
a "hot" code path, it doesn't really matter, and the next patch
will redefine num_mcast_sta to make this check invalid.
Signed-off-by: NMichael Braun <michael-dev@fami-braun.de>
[change commit message]
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Instead of building the multi-channel ops at runtime, declare
the common ops with a macro and build both that way, so that
the multi-channel ops can also be const.

As a side effect, due to the removed code, this decreases the
size of the module (while shifting data from .bss to .text
due to the newly added const).
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

sta_info_get_bss() is equivalent to sta_info_get() in the
mesh case, since sta->sdata->bss will be NULL (it's only
set for AP/AP_VLAN interfaces.) Thus, the mesh check here
isn't actually needed - remove it.
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>

Pull drm updates from Dave Airlie:
 "Core:
   - Fence destaging work
   - DRIVER_LEGACY to split off legacy drm drivers
   - drm_mm refactoring
   - Splitting drm_crtc.c into chunks and documenting better
   - Display info fixes
   - rbtree support for prime buffer lookup
   - Simple VGA DAC driver

  Panel:
   - Add Nexus 7 panel
   - More simple panels

  i915:
   - Refactoring GEM naming
   - Refactored vma/active tracking
   - Lockless request lookups
   - Better stolen memory support
   - FBC fixes
   - SKL watermark fixes
   - VGPU improvements
   - dma-buf fencing support
   - Better DP dongle support

  amdgpu:
   - Powerplay for Iceland asics
   - Improved GPU reset support
   - UVD/VEC powergating support for CZ/ST
   - Preinitialised VRAM buffer support
   - Virtual display support
   - Initial SI support
   - GTT rework
   - PCI shutdown callback support
   - HPD IRQ storm fixes

  amdkfd:
   - bugfixes

  tilcdc:
   - Atomic modesetting support

  mediatek:
   - AAL + GAMMA engine support
   - Hook up gamma LUT
   - Temporal dithering support

  imx:
   - Pixel clock from devicetree
   - drm bridge support for LVDS bridges
   - active plane reconfiguration
   - VDIC deinterlacer support
   - Frame synchronisation unit support
   - Color space conversion support

  analogix:
   - PSR support
   - Better panel on/off support

  rockchip:
   - rk3399 vop/crtc support
   - PSR support

  vc4:
   - Interlaced vblank timing
   - 3D rendering CPU overhead reduction
   - HDMI output fixes

  tda998x:
   - HDMI audio ASoC support

  sunxi:
   - Allwinner A33 support
   - better TCON support

  msm:
   - DT binding cleanups
   - Explicit fence-fd support

  sti:
   - remove sti415/416 support

  etnaviv:
   - MMUv2 refactoring
   - GC3000 support

  exynos:
   - Refactoring HDMI DCC/PHY
   - G2D pm regression fix
   - Page fault issues with wait for vblank

  There is no nouveau work in this tree, as Ben didn't get a pull
  request in, and he was fighting moving to atomic and adding mst
  support, so maybe best it waits for a cycle"

* tag 'drm-for-v4.9' of git://people.freedesktop.org/~airlied/linux: (1412 commits)
  drm/crtc: constify drm_crtc_index parameter
  drm/i915: Fix conflict resolution from backmerge of v4.8-rc8 to drm-next
  drm/i915/guc: Unwind GuC workqueue reservation if request construction fails
  drm/i915: Reset the breadcrumbs IRQ more carefully
  drm/i915: Force relocations via cpu if we run out of idle aperture
  drm/i915: Distinguish last emitted request from last submitted request
  drm/i915: Allow DP to work w/o EDID
  drm/i915: Move long hpd handling into the hotplug work
  drm/i915/execlists: Reinitialise context image after GPU hang
  drm/i915: Use correct index for backtracking HUNG semaphores
  drm/i915: Unalias obj->phys_handle and obj->userptr
  drm/i915: Just clear the mmiodebug before a register access
  drm/i915/gen9: only add the planes actually affected by ddb changes
  drm/i915: Allow PCH DPLL sharing regardless of DPLL_SDVO_HIGH_SPEED
  drm/i915/bxt: Fix HDMI DPLL configuration
  drm/i915/gen9: fix the watermark res_blocks value
  drm/i915/gen9: fix plane_blocks_per_line on watermarks calculations
  drm/i915/gen9: minimum scanlines for Y tile is not always 4
  drm/i915/gen9: fix the WaWmMemoryReadLatency implementation
  drm/i915/kbl: KBL also needs to run the SAGV code
  ...

Merge more updates from Andrew Morton:

 - a few block updates that fell in my lap

 - lib/ updates

 - checkpatch

 - autofs

 - ipc

 - a ton of misc other things

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (100 commits)
  mm: split gfp_mask and mapping flags into separate fields
  fs: use mapping_set_error instead of opencoded set_bit
  treewide: remove redundant #include <linux/kconfig.h>
  hung_task: allow hung_task_panic when hung_task_warnings is 0
  kthread: add kerneldoc for kthread_create()
  kthread: better support freezable kthread workers
  kthread: allow to modify delayed kthread work
  kthread: allow to cancel kthread work
  kthread: initial support for delayed kthread work
  kthread: detect when a kthread work is used by more workers
  kthread: add kthread_destroy_worker()
  kthread: add kthread_create_worker*()
  kthread: allow to call __kthread_create_on_node() with va_list args
  kthread/smpboot: do not park in kthread_create_on_cpu()
  kthread: kthread worker API cleanup
  kthread: rename probe_kthread_data() to kthread_probe_data()
  scripts/tags.sh: enable code completion in VIM
  mm: kmemleak: avoid using __va() on addresses that don't have a lowmem mapping
  kdump, vmcoreinfo: report memory sections virtual addresses
  ipc/sem.c: add cond_resched in exit_sme
  ...

mapping->flags currently encodes two different things into a single flag.
It contains sticky gfp_mask for page cache allocations and AS_ codes used
to report errors/enospace and other states which are mapping specific.
Condensing the two semantically unrelated things saves few bytes but it
also complicates other things.  For one thing the gfp flags space is
reduced and in fact we are already running out of available bits.  It can
be assumed that more gfp flags will be necessary later on.

To not introduce the address_space grow (at least on x86_64) we can stick
it right after private_lock because we have a hole there.

struct address_space {
        struct inode *             host;                 /*     0     8 */
        struct radix_tree_root     page_tree;            /*     8    16 */
        spinlock_t                 tree_lock;            /*    24     4 */
        atomic_t                   i_mmap_writable;      /*    28     4 */
        struct rb_root             i_mmap;               /*    32     8 */
        struct rw_semaphore        i_mmap_rwsem;         /*    40    40 */
        /* --- cacheline 1 boundary (64 bytes) was 16 bytes ago --- */
        long unsigned int          nrpages;              /*    80     8 */
        long unsigned int          nrexceptional;        /*    88     8 */
        long unsigned int          writeback_index;      /*    96     8 */
        const struct address_space_operations  * a_ops;  /*   104     8 */
        long unsigned int          flags;                /*   112     8 */
        spinlock_t                 private_lock;         /*   120     4 */

        /* XXX 4 bytes hole, try to pack */

        /* --- cacheline 2 boundary (128 bytes) --- */
        struct list_head           private_list;         /*   128    16 */
        void *                     private_data;         /*   144     8 */

        /* size: 152, cachelines: 3, members: 14 */
        /* sum members: 148, holes: 1, sum holes: 4 */
        /* last cacheline: 24 bytes */
};

Link: http://lkml.kernel.org/r/20160912114852.GI14524@dhcp22.suse.czSigned-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The mapping_set_error() helper sets the correct AS_ flag for the mapping
so there is no reason to open code it.  Use the helper directly.

[akpm@linux-foundation.org: be honest about conversion from -ENXIO to -EIO]
Link: http://lkml.kernel.org/r/20160912111608.2588-2-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Kernel source files need not include <linux/kconfig.h> explicitly
because the top Makefile forces to include it with:

  -include $(srctree)/include/linux/kconfig.h

This commit removes explicit includes except the following:

  * arch/s390/include/asm/facilities_src.h
  * tools/testing/radix-tree/linux/kernel.h

These two are used for host programs.

Link: http://lkml.kernel.org/r/1473656164-11929-1-git-send-email-yamada.masahiro@socionext.comSigned-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Previously hung_task_panic would not be respected if enabled after
hung_task_warnings had already been decremented to 0.

Permit the kernel to panic if hung_task_panic is enabled after
hung_task_warnings has already been decremented to 0 and another task
hangs for hung_task_timeout_secs seconds.

Check if hung_task_panic is enabled so we don't return prematurely, and
check if hung_task_warnings is non-zero so we don't print the warning
unnecessarily.

[akpm@linux-foundation.org: fix off-by-one]
Link: http://lkml.kernel.org/r/1473450214-4049-1-git-send-email-jsiddle@redhat.comSigned-off-by: NJohn Siddle <jsiddle@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This macro is referenced in other kerneldoc comments, but lacks one of its
own; fix that.

Link: http://lkml.kernel.org/r/20160826072313.726a3485@lwn.netSigned-off-by: NJonathan Corbet <corbet@lwn.net>
Reported-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch allows to make kthread worker freezable via a new @flags
parameter. It will allow to avoid an init work in some kthreads.

It currently does not affect the function of kthread_worker_fn()
but it might help to do some optimization or fixes eventually.

I currently do not know about any other use for the @flags
parameter but I believe that we will want more flags
in the future.

Finally, I hope that it will not cause confusion with @flags member
in struct kthread. Well, I guess that we will want to rework the
basic kthreads implementation once all kthreads are converted into
kthread workers or workqueues. It is possible that we will merge
the two structures.

Link: http://lkml.kernel.org/r/1470754545-17632-12-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are situations when we need to modify the delay of a delayed kthread
work. For example, when the work depends on an event and the initial delay
means a timeout. Then we want to queue the work immediately when the event
happens.

This patch implements kthread_mod_delayed_work() as inspired workqueues.
It cancels the timer, removes the work from any worker list and queues it
again with the given timeout.

A very special case is when the work is being canceled at the same time.
It might happen because of the regular kthread_cancel_delayed_work_sync()
or by another kthread_mod_delayed_work(). In this case, we do nothing and
let the other operation win. This should not normally happen as the caller
is supposed to synchronize these operations a reasonable way.

Link: http://lkml.kernel.org/r/1470754545-17632-11-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are going to use kthread workers more widely and sometimes we will need
to make sure that the work is neither pending nor running.

This patch implements cancel_*_sync() operations as inspired by
workqueues.  Well, we are synchronized against the other operations via
the worker lock, we use del_timer_sync() and a counter to count parallel
cancel operations.  Therefore the implementation might be easier.

First, we check if a worker is assigned.  If not, the work has newer been
queued after it was initialized.

Second, we take the worker lock.  It must be the right one.  The work must
not be assigned to another worker unless it is initialized in between.

Third, we try to cancel the timer when it exists.  The timer is deleted
synchronously to make sure that the timer call back is not running.  We
need to temporary release the worker->lock to avoid a possible deadlock
with the callback.  In the meantime, we set work->canceling counter to
avoid any queuing.

Fourth, we try to remove the work from a worker list. It might be
the list of either normal or delayed works.

Fifth, if the work is running, we call kthread_flush_work().  It might
take an arbitrary time.  We need to release the worker-lock again.  In the
meantime, we again block any queuing by the canceling counter.

As already mentioned, the check for a pending kthread work is done under a
lock.  In compare with workqueues, we do not need to fight for a single
PENDING bit to block other operations.  Therefore we do not suffer from
the thundering storm problem and all parallel canceling jobs might use
kthread_flush_work().  Any queuing is blocked until the counter gets zero.

Link: http://lkml.kernel.org/r/1470754545-17632-10-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We are going to use kthread_worker more widely and delayed works
will be pretty useful.

The implementation is inspired by workqueues.  It uses a timer to queue
the work after the requested delay.  If the delay is zero, the work is
queued immediately.

In compare with workqueues, each work is associated with a single worker
(kthread).  Therefore the implementation could be much easier.  In
particular, we use the worker->lock to synchronize all the operations with
the work.  We do not need any atomic operation with a flags variable.

In fact, we do not need any state variable at all.  Instead, we add a list
of delayed works into the worker.  Then the pending work is listed either
in the list of queued or delayed works.  And the existing check of pending
works is the same even for the delayed ones.

A work must not be assigned to another worker unless reinitialized.
Therefore the timer handler might expect that dwork->work->worker is valid
and it could simply take the lock.  We just add some sanity checks to help
with debugging a potential misuse.

Link: http://lkml.kernel.org/r/1470754545-17632-9-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Nothing currently prevents a work from queuing for a kthread worker when
it is already running on another one.  This means that the work might run
in parallel on more than one worker.  Also some operations are not
reliable, e.g.  flush.

This problem will be even more visible after we add kthread_cancel_work()
function.  It will only have "work" as the parameter and will use
worker->lock to synchronize with others.

Well, normally this is not a problem because the API users are sane.
But bugs might happen and users also might be crazy.

This patch adds a warning when we try to insert the work for another
worker.  It does not fully prevent the misuse because it would make the
code much more complicated without a big benefit.

It adds the same warning also into kthread_flush_work() instead of the
repeated attempts to get the right lock.

A side effect is that one needs to explicitly reinitialize the work if it
must be queued into another worker.  This is needed, for example, when the
worker is stopped and started again.  It is a bit inconvenient.  But it
looks like a good compromise between the stability and complexity.

I have double checked all existing users of the kthread worker API and
they all seems to initialize the work after the worker gets started.

Just for completeness, the patch adds a check that the work is not already
in a queue.

The patch also puts all the checks into a separate function.  It will be
reused when implementing delayed works.

Link: http://lkml.kernel.org/r/1470754545-17632-8-git-send-email-pmladek@suse.comSigned-off-by: NPetr Mladek <pmladek@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>