PM / QoS: Create device constraints objects on notifier registration

The current behavior of dev_pm_qos_add_notifier() makes device PM QoS
notifiers less than useful.  Namely, it silently returns success when
called before any PM QoS constraints are added for the device, so the
caller will assume that the notifier has been registered, but when
someone actually adds some nontrivial constraints for the device
eventually, the previous callers of dev_pm_qos_add_notifier()
will not know about that and their notifier routines will not be
executed (contrary to their expectations).

To address this problem make dev_pm_qos_add_notifier() create the
constraints object for the device if it is not present when the
routine is called.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by : markgross <markgross@thegnar.org>
PM / QoS: Prepare device structure for adding more constraint types

Currently struct dev_pm_info contains only one PM QoS constraints
pointer reserved for latency requirements.  Since one more device
constraints type (i.e. flags) will be necessary, introduce a new
structure, struct dev_pm_qos, that eventually will contain all of
the available device PM QoS constraints and replace the "constraints"
pointer in struct dev_pm_info with a pointer to the new structure
called "qos".

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
PM / QoS: Prepare struct dev_pm_qos_request for more request types

The subsequent patches will use struct dev_pm_qos_request for
representing both latency requests and flags requests.  To make that
easier, put the node member of struct dev_pm_qos_request (under the
name "pnode") into a union called "data" that will represent the
request's  value and list node depending on its type.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
Reviewed-by: mark gross <markgross@thegnar.org>
PM / QoS: Introduce PM QoS device flags support

Modify the device PM QoS core code to support PM QoS flags requests.

First, add a new field of type struct pm_qos_flags called "flags"
to struct dev_pm_qos for representing the list of PM QoS flags
requests for the given device.  Accordingly, add a new "type" field
to struct dev_pm_qos_request (along with an enum for representing
request types) and a new member called "flr" to its data union for
representig flags requests.

Second, modify dev_pm_qos_add_request(), dev_pm_qos_update_request(),
the internal routine apply_constraint() used by them and their
existing callers to cover flags requests as well as latency
requests.  In particular, dev_pm_qos_add_request() gets a new
argument called "type" for specifying the type of a request to be
added.

Finally, introduce two routines, __dev_pm_qos_flags() and
dev_pm_qos_flags(), allowing their callers to check which PM QoS
flags have been requested for the given device (the caller is
supposed to pass the mask of flags to check as the routine's
second argument and examine its return value for the result).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
Reviewed-by: mark gross <markgross@thegnar.org>
PM / QoS: Make it possible to expose PM QoS device flags to user space

Define two device PM QoS flags, PM_QOS_FLAG_NO_POWER_OFF
and PM_QOS_FLAG_REMOTE_WAKEUP, and introduce routines
dev_pm_qos_expose_flags() and dev_pm_qos_hide_flags() allowing the
caller to expose those two flags to user space or to hide them
from it, respectively.

After the flags have been exposed, user space will see two
additional sysfs attributes, pm_qos_no_power_off and
pm_qos_remote_wakeup, under the device's /sys/devices/.../power/
directory.  Then, writing 1 to one of them will update the
PM QoS flags request owned by user space so that the corresponding
flag is requested to be set.  In turn, writing 0 to one of them
will cause the corresponding flag in the user space's request to
be cleared (however, the owners of the other PM QoS flags requests
for the same device may still request the flag to be set and it
may be effectively set even if user space doesn't request that).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
Acked-by: mark gross <markgross@thegnar.org>
PM / QoS: Fix the return value of dev_pm_qos_update_request()

Commit e39473d (PM / QoS: Make it possible to expose PM QoS device
flags to user space) introduced __dev_pm_qos_update_request() to be
called internally by dev_pm_qos_update_request(), but forgot to make
the latter actually use the return value of the former.  Fix this
mistake.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / QoS: Fix a free error in the dev_pm_qos_constraints_destroy()

Free a wrong point to struct dev_pm_qos->latency which suppose to
be the point to struct dev_pm_qos. The patch is to fix the issue.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / QoS: Document request manipulation requirement for flags

In fact, the callers of dev_pm_qos_add_request(),
dev_pm_qos_update_request() and dev_pm_qos_remove_request() for
requests of type DEV_PM_QOS_FLAGS need to ensure that the target
device is not RPM_SUSPENDED before using any of these functions (or
be prepared for the new PM QoS flags to take effect after the device
has been resumed).  Document this in their kerneldoc comments.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / QoS: Resume device before exposing/hiding PM QoS flags

Since dev_pm_qos_add_request(), dev_pm_qos_update_request() and
dev_pm_qos_remove_request() for PM QoS flags should not be invoked
when device in RPM_SUSPENDED, add pm_runtime_get_sync() and pm_runtime_put()
around these functions in dev_pm_qos_expose_flags() and
dev_pm_qos_hide_flags().

[rjw: Modified the subject and changelog to better reflect the code
 changes made.]

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / QoS: Handle device PM QoS flags while removing constraints

PM QoS flags have to be handled by dev_pm_qos_constraints_destroy()
in the same way as PM QoS resume latency constraints.  That is, if
they have been exposed to user space, they have to be hidden from it
and the list of flags requests has to be flushed before destroying
the device's PM QoS object.  Make that happen.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / QoS: Rename local variable in dev_pm_qos_add_ancestor_request()

Local variable 'error' in dev_pm_qos_add_ancestor_request() need
not contain error codes only, so rename it to 'ret'.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM/Qos: Expose dev_pm_qos_flags symbol

The dev_pm_qos_flags() will be used in the usb core which could be
compiled as a module. This patch is to export it.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
PM / QoS: Fix concurrency issues and memory leaks in device PM QoS

The current device PM QoS code assumes that certain functions will
never be called in parallel with each other (for example, it is
assumed that dev_pm_qos_expose_flags() won't be called in parallel
with dev_pm_qos_hide_flags() for the same device and analogously
for the latency limit), which may be overly optimistic.  Moreover,
dev_pm_qos_expose_flags() and dev_pm_qos_expose_latency_limit()
leak memory in error code paths (req needs to be freed on errors)
and __dev_pm_qos_drop_user_request() forgets to free the request.

To fix the above issues put more things under the device PM QoS
mutex to make them mutually exclusive and add the missing freeing
of memory.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: Reorganize device PM initialization

Make the device power management initialization more straightforward
by moving the initialization of common (i.e. used by both runtime PM
and system suspend) fields to a separate routine.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
PM / Runtime: Allow helpers to be called by early platform drivers

Runtime PM helper functions, like pm_runtime_get_sync(), cannot be
called by early platform device drivers, because the devices' power
management locks are not initialized at that time.  This is quite
inconvenient, so modify early_platform_add_devices() to initialize
the devices power management locks as appropriate and make sure that
they won't be initialized more than once if an early platform
device is going to be used as a regular one later.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
PM / QoS: Remove device PM QoS sysfs attributes at the right place

Device PM QoS sysfs attributes, if present during device removal,
are removed from within device_pm_remove(), which is too late,
since dpm_sysfs_remove() has already removed the whole attribute
group they belonged to.  However, moving the removal of those
attributes to dpm_sysfs_remove() alone is not sufficient, because
in theory they still can be re-added right after being removed by it
(the device's driver is still bound to it at that point).

For this reason, move the entire desctruction of device PM QoS
constraints to dpm_sysfs_remove() and make it prevent any new
constraints from being added after it has run.  Also, move the
initialization of the power.qos field in struct device to
device_pm_init_common() and drop the no longer needed
dev_pm_qos_constraints_init().

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM / QoS: Avoid possible deadlock related to sysfs access

Commit b81ea1b (PM / QoS: Fix concurrency issues and memory leaks in
device PM QoS) put calls to pm_qos_sysfs_add_latency(),
pm_qos_sysfs_add_flags(), pm_qos_sysfs_remove_latency(), and
pm_qos_sysfs_remove_flags() under dev_pm_qos_mtx, which was a
mistake, because it may lead to deadlocks in some situations.
For example, if pm_qos_remote_wakeup_store() is run in parallel
with dev_pm_qos_constraints_destroy(), they may deadlock in the
following way:

 ======================================================
 [ INFO: possible circular locking dependency detected ]
 3.9.0-rc4-next-20130328-sasha-00014-g91a3267 #319 Tainted: G        W
 -------------------------------------------------------
 trinity-child6/12371 is trying to acquire lock:
  (s_active#54){++++.+}, at: [<ffffffff81301631>] sysfs_addrm_finish+0x31/0x60

 but task is already holding lock:
  (dev_pm_qos_mtx){+.+.+.}, at: [<ffffffff81f07cc3>] dev_pm_qos_constraints_destroy+0x23/0x250

 which lock already depends on the new lock.

 the existing dependency chain (in reverse order) is:

 -> #1 (dev_pm_qos_mtx){+.+.+.}:
        [<ffffffff811811da>] lock_acquire+0x1aa/0x240
        [<ffffffff83dab809>] __mutex_lock_common+0x59/0x5e0
        [<ffffffff83dabebf>] mutex_lock_nested+0x3f/0x50
        [<ffffffff81f07f2f>] dev_pm_qos_update_flags+0x3f/0xc0
        [<ffffffff81f05f4f>] pm_qos_remote_wakeup_store+0x3f/0x70
        [<ffffffff81efbb43>] dev_attr_store+0x13/0x20
        [<ffffffff812ffdaa>] sysfs_write_file+0xfa/0x150
        [<ffffffff8127f2c1>] __kernel_write+0x81/0x150
        [<ffffffff812afc2d>] write_pipe_buf+0x4d/0x80
        [<ffffffff812af57c>] splice_from_pipe_feed+0x7c/0x120
        [<ffffffff812afa25>] __splice_from_pipe+0x45/0x80
        [<ffffffff812b14fc>] splice_from_pipe+0x4c/0x70
        [<ffffffff812b1538>] default_file_splice_write+0x18/0x30
        [<ffffffff812afae3>] do_splice_from+0x83/0xb0
        [<ffffffff812afb2e>] direct_splice_actor+0x1e/0x20
        [<ffffffff812b0277>] splice_direct_to_actor+0xe7/0x200
        [<ffffffff812b15bc>] do_splice_direct+0x4c/0x70
        [<ffffffff8127eda9>] do_sendfile+0x169/0x300
        [<ffffffff8127ff94>] SyS_sendfile64+0x64/0xb0
        [<ffffffff83db7d18>] tracesys+0xe1/0xe6

 -> #0 (s_active#54){++++.+}:
        [<ffffffff811800cf>] __lock_acquire+0x15bf/0x1e50
        [<ffffffff811811da>] lock_acquire+0x1aa/0x240
        [<ffffffff81300aa2>] sysfs_deactivate+0x122/0x1a0
        [<ffffffff81301631>] sysfs_addrm_finish+0x31/0x60
        [<ffffffff812ff77f>] sysfs_hash_and_remove+0x7f/0xb0
        [<ffffffff813035a1>] sysfs_unmerge_group+0x51/0x70
        [<ffffffff81f068f4>] pm_qos_sysfs_remove_flags+0x14/0x20
        [<ffffffff81f07490>] __dev_pm_qos_hide_flags+0x30/0x70
        [<ffffffff81f07cd5>] dev_pm_qos_constraints_destroy+0x35/0x250
        [<ffffffff81f06931>] dpm_sysfs_remove+0x11/0x50
        [<ffffffff81efcf6f>] device_del+0x3f/0x1b0
        [<ffffffff81efd128>] device_unregister+0x48/0x60
        [<ffffffff82d4083c>] usb_hub_remove_port_device+0x1c/0x20
        [<ffffffff82d2a9cd>] hub_disconnect+0xdd/0x160
        [<ffffffff82d36ab7>] usb_unbind_interface+0x67/0x170
        [<ffffffff81f001a7>] __device_release_driver+0x87/0xe0
        [<ffffffff81f00559>] device_release_driver+0x29/0x40
        [<ffffffff81effc58>] bus_remove_device+0x148/0x160
        [<ffffffff81efd07f>] device_del+0x14f/0x1b0
        [<ffffffff82d344f9>] usb_disable_device+0xf9/0x280
        [<ffffffff82d34ff8>] usb_set_configuration+0x268/0x840
        [<ffffffff82d3a7fc>] usb_remove_store+0x4c/0x80
        [<ffffffff81efbb43>] dev_attr_store+0x13/0x20
        [<ffffffff812ffdaa>] sysfs_write_file+0xfa/0x150
        [<ffffffff8127f71d>] do_loop_readv_writev+0x4d/0x90
        [<ffffffff8127f999>] do_readv_writev+0xf9/0x1e0
        [<ffffffff8127faba>] vfs_writev+0x3a/0x60
        [<ffffffff8127fc60>] SyS_writev+0x50/0xd0
        [<ffffffff83db7d18>] tracesys+0xe1/0xe6

 other info that might help us debug this:

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(dev_pm_qos_mtx);
                                lock(s_active#54);
                                lock(dev_pm_qos_mtx);
   lock(s_active#54);

  *** DEADLOCK ***

To avoid that, remove the calls to functions mentioned above from
under dev_pm_qos_mtx and introduce a separate lock to prevent races
between functions that add or remove device PM QoS sysfs attributes
from happening.

Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>