linux-toradex.git/drivers/cpufreq/cpufreq.c, branch v2.6.30-rc8

[CPUFREQ] remove rwsem lock from CPUFREQ_GOV_STOP call

2009-05-26T16:04:50+00:00

* Rafael J. Wysocki (rjw@sisk.pl) wrote:
> This message has been generated automatically as a part of a report
> of regressions introduced between 2.6.28 and 2.6.29.
>
> The following bug entry is on the current list of known regressions
> introduced between 2.6.28 and 2.6.29.  Please verify if it still should
> be listed and let me know (either way).
>
>
> Bug-Entry	: http://bugzilla.kernel.org/show_bug.cgi?id=13186
> Subject		: cpufreq timer teardown problem
> Submitter	: Mathieu Desnoyers 
> Date		: 2009-04-23 14:00 (24 days old)
> References	: http://marc.info/?l=linux-kernel&m=124049523515036&w=4
> Handled-By	: Mathieu Desnoyers 
> Patch		: http://patchwork.kernel.org/patch/19754/
> 		  http://patchwork.kernel.org/patch/19753/

The patches linked above depend on the following patch to remove
circular locking dependency :

cpufreq: remove rwsem lock from CPUFREQ_GOV_STOP call

(the following issue was faced when using cancel_delayed_work_sync() in the
timer teardown (which fixes a race).

* KOSAKI Motohiro (kosaki.motohiro@jp.fujitsu.com) wrote:
> Hi
>
> my box output following warnings.
> it seems regression by commit 7ccc7608b836e58fbacf65ee4f8eefa288e86fac.
>
> A: work -> do_dbs_timer()  -> cpu_policy_rwsem
> B: store() -> cpu_policy_rwsem -> cpufreq_governor_dbs() -> work
>
>

Hrm, I think it must be due to my attempt to fix the timer teardown race
in ondemand governor mixed with new locking behavior in 2.6.30-rc.

The rwlock seems to be taken around the whole call to
cpufreq_governor_dbs(), when it should be only taken around accesses to
the locked data, and especially *not* around the call to
dbs_timer_exit().

Reverting my fix attempt would put the teardown race back in place
(replacing the cancel_delayed_work_sync by cancel_delayed_work).
Instead, a proper fix would imply modifying this critical section :

cpufreq.c: __cpufreq_remove_dev()
...
        if (cpufreq_driver->target)
                __cpufreq_governor(data, CPUFREQ_GOV_STOP);

        unlock_policy_rwsem_write(cpu);

To make sure the __cpufreq_governor() callback is not called with rwsem
held. This would allow execution of cancel_delayed_work_sync() without
being nested within the rwsem.

Applies on top of the 2.6.30-rc5 tree.

Required to remove circular dep in teardown of both conservative and
ondemande governors so they can use cancel_delayed_work_sync().
CPUFREQ_GOV_STOP does not modify the policy, therefore this locking seemed
unneeded.

Signed-off-by: Mathieu Desnoyers 
CC: KOSAKI Motohiro 
Cc: Greg KH 
CC: Ingo Molnar 
CC: "Rafael J. Wysocki" 
CC: Ben Slusky 
CC: Chris Wright 
CC: Andrew Morton 
Signed-off-by: Dave Jones

Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq

2009-03-26T18:04:08+00:00

* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/davej/cpufreq: (35 commits)
  [CPUFREQ] Prevent p4-clockmod from auto-binding to the ondemand governor.
  [CPUFREQ] Make cpufreq-nforce2 less obnoxious
  [CPUFREQ] p4-clockmod reports wrong frequency.
  [CPUFREQ] powernow-k8: Use a common exit path.
  [CPUFREQ] Change link order of x86 cpufreq modules
  [CPUFREQ] conservative: remove 10x from def_sampling_rate
  [CPUFREQ] conservative: fixup governor to function more like ondemand logic
  [CPUFREQ] conservative: fix dbs_cpufreq_notifier so freq is not locked
  [CPUFREQ] conservative: amend author's email address
  [CPUFREQ] Use swap() in longhaul.c
  [CPUFREQ] checkpatch cleanups for acpi-cpufreq
  [CPUFREQ] powernow-k8: Only print error message once, not per core.
  [CPUFREQ] ondemand/conservative: sanitize sampling_rate restrictions
  [CPUFREQ] ondemand/conservative: deprecate sampling_rate{min,max}
  [CPUFREQ] powernow-k8: Always compile powernow-k8 driver with ACPI support
  [CPUFREQ] Introduce /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_transition_latency
  [CPUFREQ] checkpatch cleanups for powernow-k8
  [CPUFREQ] checkpatch cleanups for ondemand governor.
  [CPUFREQ] checkpatch cleanups for powernow-k7
  [CPUFREQ] checkpatch cleanups for speedstep related drivers.
  ...

Revert "[CPUFREQ] Disable sysfs ui for p4-clockmod."

2009-03-09T19:07:33+00:00

This reverts commit e088e4c9cdb618675874becb91b2fd581ee707e6.

Removing the sysfs interface for p4-clockmod was flagged as a
regression in bug 12826.

Course of action:
 - Find out the remaining causes of overheating, and fix them
   if possible. ACPI should be doing the right thing automatically.
   If it isn't, we need to fix that.
 - mark p4-clockmod ui as deprecated
 - try again with the removal in six months.

It's not really feasible to printk about the deprecation, because
it needs to happen at all the sysfs entry points, which means adding
a lot of strcmp("p4-clockmod".. calls to the core, which.. bleuch.

Signed-off-by: Dave Jones

[CPUFREQ] Introduce /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_transition_latency

2009-02-25T03:47:31+00:00

It's not only useful for the ondemand and conservative governors, but
also for userspace daemons to know about the HW transition latency of
the CPU.
It is especially useful for userspace to know about this value when
the ondemand or conservative governors are run. The sampling rate
control value depends on it and for userspace being able to set sane
tuning values there it has to know about the transition latency.

Signed-off-by: Thomas Renninger 
Signed-off-by: Dave Jones

[CPUFREQ] checkpatch cleanups for cpufreq core

2009-02-25T03:47:29+00:00

Signed-off-by: Dave Jones

cpumask: convert struct cpufreq_policy to cpumask_var_t

2009-01-06T08:05:31+00:00

Impact: use new cpumask API to reduce memory usage

This is part of an effort to reduce structure sizes for machines
configured with large NR_CPUS.  cpumask_t gets replaced by
cpumask_var_t, which is either struct cpumask[1] (small NR_CPUS) or
struct cpumask * (large NR_CPUS).

Signed-off-by: Rusty Russell 
Signed-off-by: Mike Travis 
Acked-by: Dave Jones 
Signed-off-by: Ingo Molnar

[CPUFREQ] Fix on resume, now preserves user policy min/max.

2008-12-05T20:20:11+00:00

Previously driver resume would always set the current policy min/max with
the cpuinfo min/max, defined by user_policy.min/max. Resulting in a reset
of policy settings when policy.min/max != cpuinfo.min/max when coming out
of suspend. Now user_policy is saved as the policy instead of cpuinfo to
preserve what the user actually set.

Signed-off-by: Mike Chan 
Signed-off-by: Dave Jones

[CPUFREQ] Disable sysfs ui for p4-clockmod.

2008-12-05T20:20:10+00:00

p4-clockmod has a long history of abuse.   It pretends to be a CPU
frequency scaling driver, even though it doesn't actually change
the CPU frequency, but instead just modulates the frequency with
wait-states.
The biggest misconception is that when running at the lower 'frequency'
p4-clockmod is saving power.  This isn't the case, as workloads running
slower take longer to complete, preventing the CPU from entering deep C states.

However p4-clockmod does have a purpose.  It can prevent overheating.
Having it hooked up to the cpufreq interfaces is the wrong way to achieve
cooling however. It should instead be hooked up to ACPI.

This diff introduces a means for a cpufreq driver to register with the
cpufreq core, but not present a sysfs interface.

Signed-off-by: Matthew Garrett 
Signed-off-by: Dave Jones

[CPUFREQ][1/6] cpufreq: Add cpu number parameter to __cpufreq_driver_getavg()

2008-10-09T17:52:43+00:00

Add a cpu parameter to __cpufreq_driver_getavg(). This is needed for software
cpufreq coordination where policy->cpu may not be same as the CPU on which we
want to getavg frequency.

A follow-on patch will use this parameter to getavg freq from all cpus
in policy->cpus.

Change since last patch. Fix the offline/online and suspend/resume
oops reported by Youquan Song 

Signed-off-by: Venkatesh Pallipadi 
Signed-off-by: Dave Jones

[CPUFREQ] drivers/cpufreq/cpufreq.c: Adjust error handling code involving cpufreq_cpu_put

2008-10-09T17:52:43+00:00

After calling cpufreq_cpu_get, error handling code should call
cpufreq_cpu_put.

The semantic match that finds this problem is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// 
@r@
expression x,E;
statement S;
position p1,p2,p3;
@@

(
if ((x = cpufreq_cpu_get@p1(...)) == NULL || ...) S
|
x = cpufreq_cpu_get@p1(...)
... when != x
if (x == NULL || ...) S
)
<...
if@p3 (...) { ... when != cpufreq_cpu_put(x)
                  when != if (x) { ... cpufreq_cpu_put(x); ...}
    return@p2 ...;
}
...>
(
return x;
|
return 0;
|
x = E
|
E = x
|
cpufreq_cpu_put(x)
)

@exists@
position r.p1,r.p2,r.p3;
expression x;
int ret != 0;
statement S;
@@

* x = cpufreq_cpu_get@p1(...)
  <...
* if@p3 (...)
  S
  ...>
* return@p2 \(NULL\|ret\);
// 

Signed-off-by: Julia Lawall 
Signed-off-by: Dave Jones