Skip to content

L
linux
Switch branch/tag
  1. 06 Mar, 2014 5 commits
    • viresh kumar's avatar
      cpufreq: move call to __find_governor() to cpufreq_init_policy() · 6e2c89d1
      viresh kumar authored 
      We call __find_governor() during the addition of the first CPU of
each policy from __cpufreq_add_dev() to find the last governor used
for this CPU before it was hot-removed.

After that we call cpufreq_parse_governor() in cpufreq_init_policy(),
either with this governor, or with the default governor. Right after
that policy->governor is set to NULL.

While that code is not functionally problematic, the structure of it
is suboptimal, because some of the code required in cpufreq_init_policy()
is being executed by its caller, __cpufreq_add_dev(). So, it would make
more sense to get all of it together in a single place to make code more
readable.

Accordingly, move the code needed for policy initialization to
cpufreq_init_policy() and initialize policy->governor to NULL at the
beginning.

In order to clean up the code a bit more, some of the #ifdefs for
CONFIG_HOTPLUG_CPU are dropped too.
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
[rjw: Changelog]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      6e2c89d1
    • Rafael J. Wysocki's avatar
      Merge back earlier 'pm-cpufreq' material. · 3b4aff04
      Rafael J. Wysocki authored
      3b4aff04
    • Viresh Kumar's avatar
      cpufreq: Initialize governor for a new policy under policy->rwsem · 4e97b631
      Viresh Kumar authored 
      policy->rwsem is used to lock access to all parts of code modifying
struct cpufreq_policy, but it's not used on a new policy created by
__cpufreq_add_dev().

Because of that, if cpufreq_update_policy() is called in a tight loop
on one CPU in parallel with offline/online of another CPU, then the
following crash can be triggered:

Unable to handle kernel NULL pointer dereference at virtual address 00000020
pgd = c0003000
[00000020] *pgd=80000000004003, *pmd=00000000
Internal error: Oops: 206 [#1] PREEMPT SMP ARM

PC is at __cpufreq_governor+0x10/0x1ac
LR is at cpufreq_update_policy+0x114/0x150

---[ end trace f23a8defea6cd706 ]---
Kernel panic - not syncing: Fatal exception
CPU0: stopping
CPU: 0 PID: 7136 Comm: mpdecision Tainted: G      D W    3.10.0-gd727407-00074-g979ede8 #396

[<c0afe180>] (notifier_call_chain+0x40/0x68) from [<c02a23ac>] (__blocking_notifier_call_chain+0x40/0x58)
[<c02a23ac>] (__blocking_notifier_call_chain+0x40/0x58) from [<c02a23d8>] (blocking_notifier_call_chain+0x14/0x1c)
[<c02a23d8>] (blocking_notifier_call_chain+0x14/0x1c) from [<c0803c68>] (cpufreq_set_policy+0xd4/0x2b8)
[<c0803c68>] (cpufreq_set_policy+0xd4/0x2b8) from [<c0803e7c>] (cpufreq_init_policy+0x30/0x98)
[<c0803e7c>] (cpufreq_init_policy+0x30/0x98) from [<c0805a18>] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4)
[<c0805a18>] (__cpufreq_add_dev.isra.17+0x4dc/0x7a4) from [<c0805d38>] (cpufreq_cpu_callback+0x58/0x84)
[<c0805d38>] (cpufreq_cpu_callback+0x58/0x84) from [<c0afe180>] (notifier_call_chain+0x40/0x68)
[<c0afe180>] (notifier_call_chain+0x40/0x68) from [<c02812dc>] (__cpu_notify+0x28/0x44)
[<c02812dc>] (__cpu_notify+0x28/0x44) from [<c0aeed90>] (_cpu_up+0xf4/0x1dc)
[<c0aeed90>] (_cpu_up+0xf4/0x1dc) from [<c0aeeed4>] (cpu_up+0x5c/0x78)
[<c0aeeed4>] (cpu_up+0x5c/0x78) from [<c0aec808>] (store_online+0x44/0x74)
[<c0aec808>] (store_online+0x44/0x74) from [<c03a40f4>] (sysfs_write_file+0x108/0x14c)
[<c03a40f4>] (sysfs_write_file+0x108/0x14c) from [<c03517d4>] (vfs_write+0xd0/0x180)
[<c03517d4>] (vfs_write+0xd0/0x180) from [<c0351ca8>] (SyS_write+0x38/0x68)
[<c0351ca8>] (SyS_write+0x38/0x68) from [<c0205de0>] (ret_fast_syscall+0x0/0x30)

Fix that by taking locks at appropriate places in __cpufreq_add_dev()
as well.
Reported-by: default avatarSaravana Kannan <skannan@codeaurora.org>
Suggested-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
[rjw: Changelog]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      4e97b631
    • Viresh Kumar's avatar
      cpufreq: Initialize policy before making it available for others to use · 5a7e56a5
      Viresh Kumar authored 
      Policy must be fully initialized before it is being made available
for use by others. Otherwise cpufreq_cpu_get() would be able to grab
a half initialized policy structure that might not have affected_cpus
(for example) populated. Then, anybody accessing those fields will get
a wrong value and that will lead to unpredictable results.

In order to fix this, do all the necessary initialization before we
make the policy structure available via cpufreq_cpu_get(). That will
guarantee that any code accessing fields of the policy will get
correct data from them.
Reported-by: default avatarSaravana Kannan <skannan@codeaurora.org>
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
[rjw: Changelog]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      5a7e56a5
    • Aaron Plattner's avatar
      cpufreq: use cpufreq_cpu_get() to avoid cpufreq_get() race conditions · 999976e0
      Aaron Plattner authored 
      If a module calls cpufreq_get while cpufreq is initializing, it's
possible for it to be called after cpufreq_driver is set but before
cpufreq_cpu_data is written during subsys_interface_register.  This
happens because cpufreq_get doesn't take the cpufreq_driver_lock
around its use of cpufreq_cpu_data.

Fix this by using cpufreq_cpu_get(cpu) to look up the policy rather
than reading it out of cpufreq_cpu_data directly.  cpufreq_cpu_get()
takes the appropriate locks to prevent this race from happening.

Since it's possible for policy to be NULL if the caller passes in an
invalid CPU number or calls the function before cpufreq is initialized,
delete the BUG_ON(!policy) and simply return 0.  Don't try to return
-ENOENT because that's negative and the function returns an unsigned
integer.

References: https://bbs.archlinux.org/viewtopic.php?id=177934Signed-off-by: default avatarAaron Plattner <aplattner@nvidia.com>
Cc: 3.13+ <stable@vger.kernel.org> # 3.13+
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      999976e0
  3. 03 Mar, 2014 1 commit
  5. 02 Mar, 2014 15 commits
  7. 01 Mar, 2014 8 commits
  9. 28 Feb, 2014 11 commits
GitLab Nexedi Edition | About GitLab | About Nexedi | 沪ICP备2021021310号-2 | 沪ICP备2021021310号-7