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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-07-26 02:07:47 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-07-28 17:19:26 +0200
commit559ed40752dc63e68f9b9ad301b20e6a3fe5cf21 (patch)
tree8a146c24b8d1e470f071c9812d47b68c57cfecb4 /include
parent69cefc273f942bd7bb347a02e8b5b738d5f6e6f3 (diff)
downloadlinux-559ed40752dc63e68f9b9ad301b20e6a3fe5cf21.tar.bz2
cpufreq: Avoid attempts to create duplicate symbolic links
After commit 87549141d516 (cpufreq: Stop migrating sysfs files on hotplug) there is a problem with CPUs that share cpufreq policy objects with other CPUs and are initially offline. Say CPU1 shares a policy with CPU0 which is online and is registered first. As part of the registration process, cpufreq_add_dev() is called for it. It creates the policy object and a symbolic link to it from the CPU1's sysfs directory. If CPU1 is registered subsequently and it is offline at that time, cpufreq_add_dev() will attempt to create a symbolic link to the policy object for it, but that link is present already, so a warning about that will be triggered. To avoid that warning, make cpufreq use an additional CPU mask containing related CPUs that are actually present for each policy object. That mask is initialized when the policy object is populated after its creation (for the first online CPU using it) and it includes CPUs from the "policy CPUs" mask returned by the cpufreq driver's ->init() callback that are physically present at that time. Symbolic links to the policy are created only for the CPUs in that mask. If cpufreq_add_dev() is invoked for an offline CPU, it checks the new mask and only creates the symlink if the CPU was not in it (the CPU is added to the mask at the same time). In turn, cpufreq_remove_dev() drops the given CPU from the new mask, removes its symlink to the policy object and returns, unless it is the CPU owning the policy object. In that case, the policy object is moved to a new CPU's sysfs directory or deleted if the CPU being removed was the last user of the policy. While at it, notice that cpufreq_remove_dev() can't fail, because its return value is ignored, so make it ignore return values from __cpufreq_remove_dev_prepare() and __cpufreq_remove_dev_finish() and prevent these functions from aborting on errors returned by __cpufreq_governor(). Also drop the now unused sif argument from them. Fixes: 87549141d516 (cpufreq: Stop migrating sysfs files on hotplug) Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reported-and-tested-by: Russell King <linux@arm.linux.org.uk> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/cpufreq.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 29ad97c34fd5..bde1e567b3a9 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -62,6 +62,7 @@ struct cpufreq_policy {
/* CPUs sharing clock, require sw coordination */
cpumask_var_t cpus; /* Online CPUs only */
cpumask_var_t related_cpus; /* Online + Offline CPUs */
+ cpumask_var_t real_cpus; /* Related and present */
unsigned int shared_type; /* ACPI: ANY or ALL affected CPUs
should set cpufreq */