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  1. 06 1月, 2014 4 次提交
    • V
      cpufreq: Make sure CPU is running on a freq from freq-table · d3916691
      由 Viresh Kumar 提交于 
      Sometimes boot loaders set CPU frequency to a value outside of frequency table
present with cpufreq core. In such cases CPU might be unstable if it has to run
on that frequency for long duration of time and so its better to set it to a
frequency which is specified in freq-table. This also makes cpufreq stats
inconsistent as cpufreq-stats would fail to register because current frequency
of CPU isn't found in freq-table.

Because we don't want this change to affect boot process badly, we go for the
next freq which is >= policy->cur ('cur' must be set by now, otherwise we will
end up setting freq to lowest of the table as 'cur' is initialized to zero).

In case current frequency doesn't match any frequency from freq-table, we throw
warnings to user, so that user can get this fixed in their bootloaders or
freq-tables.
Reported-by: NCarlos Hernandez <ceh@ti.com>
Reported-and-tested-by: NNishanth Menon <nm@ti.com>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      d3916691
    • V
      cpufreq: send new set of notification for transition failures · ab1b1c4e
      由 Viresh Kumar 提交于 
      In the current code, if we fail during a frequency transition, we
simply send the POSTCHANGE notification with the old frequency. This
isn't enough.

One of the core users of these notifications is the code responsible
for keeping loops_per_jiffy aligned with frequency changes. And mostly
it is written as:

	if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
	    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
		update-loops-per-jiffy...
	}

So, suppose we are changing to a higher frequency and failed during
transition, then following will happen:
- CPUFREQ_PRECHANGE notification with freq-new > freq-old
- CPUFREQ_POSTCHANGE notification with freq-new == freq-old

The first one will update loops_per_jiffy and second one will do
nothing. Even if we send the 2nd notification by exchanging values of
freq-new and old, some users of these notifications might get
unstable.

This can be fixed by simply calling cpufreq_notify_post_transition()
with error code and this routine will take care of sending
notifications in the correct order.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
[rjw: Folded 3 patches into one, rebased unicore2 changes]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      ab1b1c4e
    • V
      cpufreq: Introduce cpufreq_notify_post_transition() · f7ba3b41
      由 Viresh Kumar 提交于 
      This introduces a new routine cpufreq_notify_post_transition() which
can be used to send POSTCHANGE notification for new freq with or
without both {PRE|POST}CHANGE notifications for last freq. This is
useful at multiple places, especially for sending transition failure
notifications.
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      f7ba3b41
    • J
      cpufreq: Fix timer/workqueue corruption by protecting reading governor_enabled · 6f1e4efd
      由 Jane Li 提交于 
      When a CPU is hot removed we'll cancel all the delayed work items via
gov_cancel_work(). Sometimes the delayed work function determines that
it should adjust the delay for all other CPUs that the policy is
managing. If this scenario occurs, the canceling CPU will cancel its own
work but queue up the other CPUs works to run.

Commit 3617f2 (cpufreq: Fix timer/workqueue corruption due to double
queueing) has tried to fix this, but reading governor_enabled is not
protected by cpufreq_governor_lock. Even though od_dbs_timer() checks
governor_enabled before gov_queue_work(), this scenario may occur. For
example:

 CPU0                                        CPU1
 ----                                        ----
 cpu_down()
  ...                                        <work runs>
  __cpufreq_remove_dev()                     od_dbs_timer()
   __cpufreq_governor()                       policy->governor_enabled
    policy->governor_enabled = false;
    cpufreq_governor_dbs()
     case CPUFREQ_GOV_STOP:
      gov_cancel_work(dbs_data, policy);
       cpu0 work is canceled
        timer is canceled
        cpu1 work is canceled
        <waits for cpu1>
                                              gov_queue_work(*, *, true);
                                               cpu0 work queued
                                               cpu1 work queued
                                               cpu2 work queued
                                               ...
        cpu1 work is canceled
        cpu2 work is canceled
        ...

At the end of the GOV_STOP case cpu0 still has a work queued to
run although the code is expecting all of the works to be
canceled. __cpufreq_remove_dev() will then proceed to
re-initialize all the other CPUs works except for the CPU that is
going down. The CPUFREQ_GOV_START case in cpufreq_governor_dbs()
will trample over the queued work and debugobjects will spit out
a warning:

WARNING: at lib/debugobjects.c:260 debug_print_object+0x94/0xbc()
ODEBUG: init active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x14
Modules linked in:
CPU: 1 PID: 1205 Comm: sh Tainted: G        W    3.10.0 #200
[<c01144f0>] (unwind_backtrace+0x0/0xf8) from [<c0111d98>] (show_stack+0x10/0x14)
[<c0111d98>] (show_stack+0x10/0x14) from [<c01272cc>] (warn_slowpath_common+0x4c/0x68)
[<c01272cc>] (warn_slowpath_common+0x4c/0x68) from [<c012737c>] (warn_slowpath_fmt+0x30/0x40)
[<c012737c>] (warn_slowpath_fmt+0x30/0x40) from [<c034c640>] (debug_print_object+0x94/0xbc)
[<c034c640>] (debug_print_object+0x94/0xbc) from [<c034c7f8>] (__debug_object_init+0xc8/0x3c0)
[<c034c7f8>] (__debug_object_init+0xc8/0x3c0) from [<c01360e0>] (init_timer_key+0x20/0x104)
[<c01360e0>] (init_timer_key+0x20/0x104) from [<c04872ac>] (cpufreq_governor_dbs+0x1dc/0x68c)
[<c04872ac>] (cpufreq_governor_dbs+0x1dc/0x68c) from [<c04833a8>] (__cpufreq_governor+0x80/0x1b0)
[<c04833a8>] (__cpufreq_governor+0x80/0x1b0) from [<c0483704>] (__cpufreq_remove_dev.isra.12+0x22c/0x380)
[<c0483704>] (__cpufreq_remove_dev.isra.12+0x22c/0x380) from [<c0692f38>] (cpufreq_cpu_callback+0x48/0x5c)
[<c0692f38>] (cpufreq_cpu_callback+0x48/0x5c) from [<c014fb40>] (notifier_call_chain+0x44/0x84)
[<c014fb40>] (notifier_call_chain+0x44/0x84) from [<c012ae44>] (__cpu_notify+0x2c/0x48)
[<c012ae44>] (__cpu_notify+0x2c/0x48) from [<c068dd40>] (_cpu_down+0x80/0x258)
[<c068dd40>] (_cpu_down+0x80/0x258) from [<c068df40>] (cpu_down+0x28/0x3c)
[<c068df40>] (cpu_down+0x28/0x3c) from [<c068e4c0>] (store_online+0x30/0x74)
[<c068e4c0>] (store_online+0x30/0x74) from [<c03a7308>] (dev_attr_store+0x18/0x24)
[<c03a7308>] (dev_attr_store+0x18/0x24) from [<c0256fe0>] (sysfs_write_file+0x100/0x180)
[<c0256fe0>] (sysfs_write_file+0x100/0x180) from [<c01fec9c>] (vfs_write+0xbc/0x184)
[<c01fec9c>] (vfs_write+0xbc/0x184) from [<c01ff034>] (SyS_write+0x40/0x68)
[<c01ff034>] (SyS_write+0x40/0x68) from [<c010e200>] (ret_fast_syscall+0x0/0x48)

In gov_queue_work(), lock cpufreq_governor_lock before gov_queue_work,
and unlock it after __gov_queue_work(). In this way, governor_enabled
is guaranteed not changed in gov_queue_work().
Signed-off-by: NJane Li <jiel@marvell.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      6f1e4efd
  3. 29 12月, 2013 2 次提交
  5. 22 12月, 2013 2 次提交
    • J
      cpufreq: Use CONFIG_CPU_FREQ_DEFAULT_* to set initial policy for setpolicy drivers · a27a9ab7
      由 Jason Baron 提交于 
      When configuring a default governor (via CONFIG_CPU_FREQ_DEFAULT_*) with the
intel_pstate driver, the desired default policy is not properly set. For
example, setting 'CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE' ends up with the
'powersave' policy being set.

Fix by configuring the correct default policy, if either 'powersave' or
'performance' are requested. Otherwise, fallback to what the driver originally
set via its 'init' routine.
Signed-off-by: NJason Baron <jbaron@akamai.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      a27a9ab7
    • V
      cpufreq: remove sysfs files for CPUs which failed to come back after resume · 42f921a6
      由 Viresh Kumar 提交于 
      There are cases where cpufreq_add_dev() may fail for some CPUs
during system resume. With the current code we will still have
sysfs cpufreq files for those CPUs and struct cpufreq_policy
would be already freed for them. Hence any operation on those
sysfs files would result in kernel warnings.

Example of problems resulting from resume errors (from Bjørn Mork):

WARNING: CPU: 0 PID: 6055 at fs/sysfs/file.c:343 sysfs_open_file+0x77/0x212()
missing sysfs attribute operations for kobject: (null)
Modules linked in: [stripped as irrelevant]
CPU: 0 PID: 6055 Comm: grep Tainted: G      D      3.13.0-rc2 #153
Hardware name: LENOVO 2776LEG/2776LEG, BIOS 6EET55WW (3.15 ) 12/19/2011
 0000000000000009 ffff8802327ebb78 ffffffff81380b0e 0000000000000006
 ffff8802327ebbc8 ffff8802327ebbb8 ffffffff81038635 0000000000000000
 ffffffff811823c7 ffff88021a19e688 ffff88021a19e688 ffff8802302f9310
Call Trace:
 [<ffffffff81380b0e>] dump_stack+0x55/0x76
 [<ffffffff81038635>] warn_slowpath_common+0x7c/0x96
 [<ffffffff811823c7>] ? sysfs_open_file+0x77/0x212
 [<ffffffff810386e3>] warn_slowpath_fmt+0x41/0x43
 [<ffffffff81182dec>] ? sysfs_get_active+0x6b/0x82
 [<ffffffff81182382>] ? sysfs_open_file+0x32/0x212
 [<ffffffff811823c7>] sysfs_open_file+0x77/0x212
 [<ffffffff81182350>] ? sysfs_schedule_callback+0x1ac/0x1ac
 [<ffffffff81122562>] do_dentry_open+0x17c/0x257
 [<ffffffff8112267e>] finish_open+0x41/0x4f
 [<ffffffff81130225>] do_last+0x80c/0x9ba
 [<ffffffff8112dbbd>] ? inode_permission+0x40/0x42
 [<ffffffff81130606>] path_openat+0x233/0x4a1
 [<ffffffff81130b7e>] do_filp_open+0x35/0x85
 [<ffffffff8113b787>] ? __alloc_fd+0x172/0x184
 [<ffffffff811232ea>] do_sys_open+0x6b/0xfa
 [<ffffffff811233a7>] SyS_openat+0xf/0x11
 [<ffffffff8138c812>] system_call_fastpath+0x16/0x1b

To fix this, remove those sysfs files or put the associated kobject
in case of such errors. Also, to make it simple, remove the cpufreq
sysfs links from all the CPUs (except for the policy->cpu) during
suspend, as that operation won't result in a loss of sysfs file
permissions and we can create those links during resume just fine.

Fixes: 5302c3fb ("cpufreq: Perform light-weight init/teardown during suspend/resume")
Reported-and-tested-by: NBjørn Mork <bjorn@mork.no>
Signed-off-by: NViresh Kumar <viresh.kumar@linaro.org>
Cc: 3.12+ <stable@vger.kernel.org> # 3.12+
[rjw: Changelog]
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      42f921a6
  7. 08 12月, 2013 2 次提交
  9. 03 12月, 2013 1 次提交
    • B
      cpufreq: fix garbage kobjects on errors during suspend/resume · 2167e239
      由 Bjørn Mork 提交于 
      This is effectively a revert of commit 5302c3fb ("cpufreq: Perform
light-weight init/teardown during suspend/resume"), which enabled
suspend/resume optimizations leaving the sysfs files in place.

Errors during suspend/resume are not handled properly, leaving
dead sysfs attributes in case of failures.  There are are number of
functions with special code for the "frozen" case, and all these
need to also have special error handling.

The problem is easy to demonstrate by making cpufreq_driver->init()
or cpufreq_driver->get() fail during resume.

The code is too complex for a simple fix, with split code paths
in multiple blocks within a number of functions.  It is therefore
best to revert the patch enabling this code until the error handling
is in place.

Examples of problems resulting from resume errors:

WARNING: CPU: 0 PID: 6055 at fs/sysfs/file.c:343 sysfs_open_file+0x77/0x212()
missing sysfs attribute operations for kobject: (null)
Modules linked in: [stripped as irrelevant]
CPU: 0 PID: 6055 Comm: grep Tainted: G      D      3.13.0-rc2 #153
Hardware name: LENOVO 2776LEG/2776LEG, BIOS 6EET55WW (3.15 ) 12/19/2011
 0000000000000009 ffff8802327ebb78 ffffffff81380b0e 0000000000000006
 ffff8802327ebbc8 ffff8802327ebbb8 ffffffff81038635 0000000000000000
 ffffffff811823c7 ffff88021a19e688 ffff88021a19e688 ffff8802302f9310
Call Trace:
 [<ffffffff81380b0e>] dump_stack+0x55/0x76
 [<ffffffff81038635>] warn_slowpath_common+0x7c/0x96
 [<ffffffff811823c7>] ? sysfs_open_file+0x77/0x212
 [<ffffffff810386e3>] warn_slowpath_fmt+0x41/0x43
 [<ffffffff81182dec>] ? sysfs_get_active+0x6b/0x82
 [<ffffffff81182382>] ? sysfs_open_file+0x32/0x212
 [<ffffffff811823c7>] sysfs_open_file+0x77/0x212
 [<ffffffff81182350>] ? sysfs_schedule_callback+0x1ac/0x1ac
 [<ffffffff81122562>] do_dentry_open+0x17c/0x257
 [<ffffffff8112267e>] finish_open+0x41/0x4f
 [<ffffffff81130225>] do_last+0x80c/0x9ba
 [<ffffffff8112dbbd>] ? inode_permission+0x40/0x42
 [<ffffffff81130606>] path_openat+0x233/0x4a1
 [<ffffffff81130b7e>] do_filp_open+0x35/0x85
 [<ffffffff8113b787>] ? __alloc_fd+0x172/0x184
 [<ffffffff811232ea>] do_sys_open+0x6b/0xfa
 [<ffffffff811233a7>] SyS_openat+0xf/0x11
 [<ffffffff8138c812>] system_call_fastpath+0x16/0x1b

The failure to restore cpufreq devices on cancelled hibernation is
not a new bug. It is caused by the ACPI _PPC call failing unless the
hibernate is completed. This makes the acpi_cpufreq driver fail its
init.

Previously, the cpufreq device could be restored by offlining the
cpu temporarily.  And as a complete hibernation cycle would do this,
it would be automatically restored most of the time.  But after
commit 5302c3fb the leftover sysfs attributes will block any
device add action.  Therefore offlining and onlining CPU 1 will no
longer restore the cpufreq object, and a complete suspend/resume
cycle will replace it with garbage.

Fixes: 5302c3fb ("cpufreq: Perform light-weight init/teardown during suspend/resume")
Cc: 3.12+ <stable@vger.kernel.org> # 3.12+
Signed-off-by: NBjørn Mork <bjorn@mork.no>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      2167e239
  11. 28 11月, 2013 1 次提交
  13. 31 10月, 2013 1 次提交
  15. 26 10月, 2013 2 次提交
  17. 17 10月, 2013 1 次提交
  19. 16 10月, 2013 9 次提交
  21. 10 10月, 2013 1 次提交
  23. 25 9月, 2013 1 次提交
  25. 20 9月, 2013 1 次提交
  27. 18 9月, 2013 2 次提交
  29. 12 9月, 2013 4 次提交
    • L
      cpufreq: Acquire the lock in cpufreq_policy_restore() for reading · 44871c9c
      由 Lan Tianyu 提交于 
      In cpufreq_policy_restore() before system suspend policy is read from
percpu's cpufreq_cpu_data_fallback.  It's a read operation rather
than a write one, so take the lock for reading in there.
Signed-off-by: NLan Tianyu <tianyu.lan@intel.com>
Reviewed-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      44871c9c
    • S
      cpufreq: Prevent problems in update_policy_cpu() if last_cpu == new_cpu · cb38ed5c
      由 Srivatsa S. Bhat 提交于 
      If update_policy_cpu() is invoked with the existing policy->cpu itself
as the new-cpu parameter, then a lot of things can go terribly wrong.

In its present form, update_policy_cpu() always assumes that the new-cpu
is different from policy->cpu and invokes other functions to perform their
respective updates. And those functions implement the actual update like
this:

per_cpu(..., new_cpu) = per_cpu(..., last_cpu);
per_cpu(..., last_cpu) = NULL;

Thus, when new_cpu == last_cpu, the final NULL assignment makes the per-cpu
references vanish into thin air! (memory leak). From there, it leads to more
problems: cpufreq_stats_create_table() now doesn't find the per-cpu reference
and hence tries to create a new sysfs-group; but sysfs already had created
the group earlier, so it complains that it cannot create a duplicate filename.
In short, the repercussions of a rather innocuous invocation of
update_policy_cpu() can turn out to be pretty nasty.

Ideally update_policy_cpu() should handle this situation (new == last)
gracefully, and not lead to such severe problems. So fix it by adding an
appropriate check.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Tested-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      cb38ed5c
    • S
      cpufreq: Restructure if/else block to avoid unintended behavior · 61173f25
      由 Srivatsa S. Bhat 提交于 
      In __cpufreq_remove_dev_prepare(), the code which decides whether to remove
the sysfs link or nominate a new policy cpu, is governed by an if/else block
with a rather complex set of conditionals. Worse, they harbor a subtlety
which leads to certain unintended behavior.

The code looks like this:

        if (cpu != policy->cpu && !frozen) {
                sysfs_remove_link(&dev->kobj, "cpufreq");
        } else if (cpus > 1) {
		new_cpu = cpufreq_nominate_new_policy_cpu(...);
		...
		update_policy_cpu(..., new_cpu);
	}

The original intention was:
If the CPU going offline is not policy->cpu, just remove the link.
On the other hand, if the CPU going offline is the policy->cpu itself,
handover the policy->cpu job to some other surviving CPU in that policy.

But because the 'if' condition also includes the 'frozen' check, now there
are *two* possibilities by which we can enter the 'else' block:

1. cpu == policy->cpu (intended)
2. cpu != policy->cpu && frozen (unintended)

Due to the second (unintended) scenario, we end up spuriously nominating
a CPU as the policy->cpu, even when the existing policy->cpu is alive and
well. This can cause problems further down the line, especially when we end
up nominating the same policy->cpu as the new one (ie., old == new),
because it totally confuses update_policy_cpu().

To avoid this mess, restructure the if/else block to only do what was
originally intended, and thus prevent any unwelcome surprises.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Tested-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      61173f25
    • S
      cpufreq: Fix crash in cpufreq-stats during suspend/resume · 0d66b91e
      由 Srivatsa S. Bhat 提交于 
      Stephen Warren reported that the cpufreq-stats code hits a NULL pointer
dereference during the second attempt to suspend a system. He also
pin-pointed the problem to commit 5302c3fb "cpufreq: Perform light-weight
init/teardown during suspend/resume".

That commit actually ensured that the cpufreq-stats table and the
cpufreq-stats sysfs entries are *not* torn down (ie., not freed) during
suspend/resume, which makes it all the more surprising. However, it turns
out that the root-cause is not that we access an already freed memory, but
that the reference to the allocated memory gets moved around and we lose
track of that during resume, leading to the reported crash in a subsequent
suspend attempt.

In the suspend path, during CPU offline, the value of policy->cpu is updated
by choosing one of the surviving CPUs in that policy, as long as there is
atleast one CPU in that policy. And cpufreq_stats_update_policy_cpu() is
invoked to update the reference to the stats structure by assigning it to
the new CPU. However, in the resume path, during CPU online, we end up
assigning a fresh CPU as the policy->cpu, without letting cpufreq-stats
know about this. Thus the reference to the stats structure remains
(incorrectly) associated with the old CPU. So, in a subsequent suspend attempt,
during CPU offline, we end up accessing an incorrect location to get the
stats structure, which eventually leads to the NULL pointer dereference.

Fix this by letting cpufreq-stats know about the update of the policy->cpu
during CPU online in the resume path. (Also, move the update_policy_cpu()
function higher up in the file, so that __cpufreq_add_dev() can invoke
it).
Reported-and-tested-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      0d66b91e
  31. 10 9月, 2013 6 次提交
    • R
      Revert "cpufreq: make sure frequency transitions are serialized" · 798282a8
      由 Rafael J. Wysocki 提交于 
      Commit 7c30ed53 (cpufreq: make sure frequency transitions are
serialized) attempted to serialize frequency transitions by
adding checks to the CPUFREQ_PRECHANGE and CPUFREQ_POSTCHANGE
notifications.  However, it assumed that the notifications will
always originate from the driver's .target() callback, but they
also can be triggered by cpufreq_out_of_sync() and that leads to
warnings like this on some systems:

 WARNING: CPU: 0 PID: 14543 at drivers/cpufreq/cpufreq.c:317
 __cpufreq_notify_transition+0x238/0x260()
 In middle of another frequency transition

accompanied by a call trace similar to this one:

 [<ffffffff81720daa>] dump_stack+0x46/0x58
 [<ffffffff8106534c>] warn_slowpath_common+0x8c/0xc0
 [<ffffffff815b8560>] ? acpi_cpufreq_target+0x320/0x320
 [<ffffffff81065436>] warn_slowpath_fmt+0x46/0x50
 [<ffffffff815b1ec8>] __cpufreq_notify_transition+0x238/0x260
 [<ffffffff815b33be>] cpufreq_notify_transition+0x3e/0x70
 [<ffffffff815b345d>] cpufreq_out_of_sync+0x6d/0xb0
 [<ffffffff815b370c>] cpufreq_update_policy+0x10c/0x160
 [<ffffffff815b3760>] ? cpufreq_update_policy+0x160/0x160
 [<ffffffff81413813>] cpufreq_set_cur_state+0x8c/0xb5
 [<ffffffff814138df>] processor_set_cur_state+0xa3/0xcf
 [<ffffffff8158e13c>] thermal_cdev_update+0x9c/0xb0
 [<ffffffff8159046a>] step_wise_throttle+0x5a/0x90
 [<ffffffff8158e21f>] handle_thermal_trip+0x4f/0x140
 [<ffffffff8158e377>] thermal_zone_device_update+0x57/0xa0
 [<ffffffff81415b36>] acpi_thermal_check+0x2e/0x30
 [<ffffffff81415ca0>] acpi_thermal_notify+0x40/0xdc
 [<ffffffff813e7dbd>] acpi_device_notify+0x19/0x1b
 [<ffffffff813f8241>] acpi_ev_notify_dispatch+0x41/0x5c
 [<ffffffff813e3fbe>] acpi_os_execute_deferred+0x25/0x32
 [<ffffffff81081060>] process_one_work+0x170/0x4a0
 [<ffffffff81082121>] worker_thread+0x121/0x390
 [<ffffffff81082000>] ? manage_workers.isra.20+0x170/0x170
 [<ffffffff81088fe0>] kthread+0xc0/0xd0
 [<ffffffff81088f20>] ? flush_kthread_worker+0xb0/0xb0
 [<ffffffff8173582c>] ret_from_fork+0x7c/0xb0
 [<ffffffff81088f20>] ? flush_kthread_worker+0xb0/0xb0

For this reason, revert commit 7c30ed53 along with the fix 266c13d7
(cpufreq: Fix serialization of frequency transitions) on top of it
and we will revisit the serialization problem later.
Reported-by: NAlessandro Bono <alessandro.bono@gmail.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      798282a8
    • S
      cpufreq: Use signed type for 'ret' variable, to store negative error values · 5136fa56
      由 Srivatsa S. Bhat 提交于 
      There are places where the variable 'ret' is declared as unsigned int
and then used to store negative return values such as -EINVAL. Fix them
by declaring the variable as a signed quantity.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      5136fa56
    • S
      cpufreq: Remove temporary fix for race between CPU hotplug and sysfs-writes · 56d07db2
      由 Srivatsa S. Bhat 提交于 
      Commit "cpufreq: serialize calls to __cpufreq_governor()" had been a temporary
and partial solution to the race condition between writing to a cpufreq sysfs
file and taking a CPU offline. Now that we have a proper and complete solution
to that problem, remove the temporary fix.
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      56d07db2
    • S
      cpufreq: Synchronize the cpufreq store_*() routines with CPU hotplug · 4f750c93
      由 Srivatsa S. Bhat 提交于 
      The functions that are used to write to cpufreq sysfs files (such as
store_scaling_max_freq()) are not hotplug safe. They can race with CPU
hotplug tasks and lead to problems such as trying to acquire an already
destroyed timer-mutex etc.

Eg:

    __cpufreq_remove_dev()
     __cpufreq_governor(policy, CPUFREQ_GOV_STOP);
       policy->governor->governor(policy, CPUFREQ_GOV_STOP);
        cpufreq_governor_dbs()
         case CPUFREQ_GOV_STOP:
          mutex_destroy(&cpu_cdbs->timer_mutex)
          cpu_cdbs->cur_policy = NULL;
      <PREEMPT>
    store()
     __cpufreq_set_policy()
      __cpufreq_governor(policy, CPUFREQ_GOV_LIMITS);
        policy->governor->governor(policy, CPUFREQ_GOV_LIMITS);
         case CPUFREQ_GOV_LIMITS:
          mutex_lock(&cpu_cdbs->timer_mutex); <-- Warning (destroyed mutex)
           if (policy->max < cpu_cdbs->cur_policy->cur) <- cur_policy == NULL

So use get_online_cpus()/put_online_cpus() in the store_*() functions, to
synchronize with CPU hotplug. However, there is an additional point to note
here: some parts of the CPU teardown in the cpufreq subsystem are done in
the CPU_POST_DEAD stage, with cpu_hotplug.lock *released*. So, using the
get/put_online_cpus() functions alone is insufficient; we should also ensure
that we don't race with those latter steps in the hotplug sequence. We can
easily achieve this by checking if the CPU is online before proceeding with
the store, since the CPU would have been marked offline by the time the
CPU_POST_DEAD notifiers are executed.
Reported-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      4f750c93
    • S
      cpufreq: Invoke __cpufreq_remove_dev_finish() after releasing cpu_hotplug.lock · 1aee40ac
      由 Srivatsa S. Bhat 提交于 
      __cpufreq_remove_dev_finish() handles the kobject cleanup for a CPU going
offline. But because we destroy the kobject towards the end of the CPU offline
phase, there are certain race windows where a task can try to write to a
cpufreq sysfs file (eg: using store_scaling_max_freq()) while we are taking
that CPU offline, and this can bump up the kobject refcount, which in turn might
hinder the CPU offline task from running to completion. (It can also cause
other more serious problems such as trying to acquire a destroyed timer-mutex
etc., depending on the exact stage of the cleanup at which the task managed to
take a new refcount).

To fix the race window, we will need to synchronize those store_*() call-sites
with CPU hotplug, using get_online_cpus()/put_online_cpus(). However, that
in turn can cause a total deadlock because it can end up waiting for the
CPU offline task to complete, with incremented refcount!

Write to sysfs                            CPU offline task
--------------                            ----------------
kobj_refcnt++

                                          Acquire cpu_hotplug.lock

get_online_cpus();

					  Wait for kobj_refcnt to drop to zero

                     **DEADLOCK**

A simple way to avoid this problem is to perform the kobject cleanup in the
CPU offline path, with the cpu_hotplug.lock *released*. That is, we can
perform the wait-for-kobj-refcnt-to-drop as well as the subsequent cleanup
in the CPU_POST_DEAD stage of CPU offline, which is run with cpu_hotplug.lock
released. Doing this helps us avoid deadlocks due to holding kobject refcounts
and waiting on each other on the cpu_hotplug.lock.

(Note: We can't move all of the cpufreq CPU offline steps to the
CPU_POST_DEAD stage, because certain things such as stopping the governors
have to be done before the outgoing CPU is marked offline. So retain those
parts in the CPU_DOWN_PREPARE stage itself).
Reported-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      1aee40ac
    • S
      cpufreq: Split __cpufreq_remove_dev() into two parts · cedb70af
      由 Srivatsa S. Bhat 提交于 
      During CPU offline, the cpufreq core invokes __cpufreq_remove_dev()
to perform work such as stopping the cpufreq governor, clearing the
CPU from the policy structure etc, and finally cleaning up the
kobject.

There are certain subtle issues related to the kobject cleanup, and
it would be much easier to deal with them if we separate that part
from the rest of the cleanup-work in the CPU offline phase. So split
the __cpufreq_remove_dev() function into 2 parts: one that handles
the kobject cleanup, and the other that handles the rest of the work.
Reported-by: NStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
      cedb70af