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authorViresh Kumar <viresh.kumar@linaro.org>2016-02-09 06:31:33 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-03-09 16:40:58 +0300
commitc4435630361d9bebf7154a0c842dc1fb7ae39c99 (patch)
tree6b8eeab3ceb2fa74d260708e8310990586d87f6b /drivers/cpufreq/cpufreq_ondemand.c
parentff4b17895e3166084c76ae703cb1c757bcc59799 (diff)
downloadlinux-c4435630361d9bebf7154a0c842dc1fb7ae39c99.tar.xz
cpufreq: governor: New sysfs show/store callbacks for governor tunables
The ondemand and conservative governors use the global-attr or freq-attr structures to represent sysfs attributes corresponding to their tunables (which of them is actually used depends on whether or not different policy objects can use the same governor with different tunables at the same time and, consequently, on where those attributes are located in sysfs). Unfortunately, in the freq-attr case, the standard cpufreq show/store sysfs attribute callbacks are applied to the governor tunable attributes and they always acquire the policy->rwsem lock before carrying out the operation. That may lead to an ABBA deadlock if governor tunable attributes are removed under policy->rwsem while one of them is being accessed concurrently (if sysfs attributes removal wins the race, it will wait for the access to complete with policy->rwsem held while the attribute callback will block on policy->rwsem indefinitely). We attempted to address this issue by dropping policy->rwsem around governor tunable attributes removal (that is, around invocations of the ->governor callback with the event arg equal to CPUFREQ_GOV_POLICY_EXIT) in cpufreq_set_policy(), but that opened up race conditions that had not been possible with policy->rwsem held all the time. Therefore policy->rwsem cannot be dropped in cpufreq_set_policy() at any point, but the deadlock situation described above must be avoided too. To that end, use the observation that in principle governor tunables may be represented by the same data type regardless of whether the governor is system-wide or per-policy and introduce a new structure, struct governor_attr, for representing them and new corresponding macros for creating show/store sysfs callbacks for them. Also make their parent kobject use a new kobject type whose default show/store callbacks are not related to the standard core cpufreq ones in any way (and they don't acquire policy->rwsem in particular). Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Tested-by: Juri Lelli <juri.lelli@arm.com> Tested-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> [ rjw: Subject & changelog + rebase ] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq/cpufreq_ondemand.c')
-rw-r--r--drivers/cpufreq/cpufreq_ondemand.c72
1 files changed, 25 insertions, 47 deletions
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 13c64b662fa1..e36792f60348 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -432,54 +432,33 @@ static ssize_t store_powersave_bias(struct dbs_data *dbs_data, const char *buf,
return count;
}
-show_store_one(od, io_is_busy);
-show_store_one(od, powersave_bias);
-show_store_one_common(od, sampling_rate);
-show_store_one_common(od, up_threshold);
-show_store_one_common(od, sampling_down_factor);
-show_store_one_common(od, ignore_nice_load);
-show_one_common(od, min_sampling_rate);
-
-gov_sys_pol_attr_rw(sampling_rate);
-gov_sys_pol_attr_rw(io_is_busy);
-gov_sys_pol_attr_rw(up_threshold);
-gov_sys_pol_attr_rw(sampling_down_factor);
-gov_sys_pol_attr_rw(ignore_nice_load);
-gov_sys_pol_attr_rw(powersave_bias);
-gov_sys_pol_attr_ro(min_sampling_rate);
-
-static struct attribute *dbs_attributes_gov_sys[] = {
- &min_sampling_rate_gov_sys.attr,
- &sampling_rate_gov_sys.attr,
- &up_threshold_gov_sys.attr,
- &sampling_down_factor_gov_sys.attr,
- &ignore_nice_load_gov_sys.attr,
- &powersave_bias_gov_sys.attr,
- &io_is_busy_gov_sys.attr,
+gov_show_one_common(sampling_rate);
+gov_show_one_common(up_threshold);
+gov_show_one_common(sampling_down_factor);
+gov_show_one_common(ignore_nice_load);
+gov_show_one_common(min_sampling_rate);
+gov_show_one(od, io_is_busy);
+gov_show_one(od, powersave_bias);
+
+gov_attr_rw(sampling_rate);
+gov_attr_rw(io_is_busy);
+gov_attr_rw(up_threshold);
+gov_attr_rw(sampling_down_factor);
+gov_attr_rw(ignore_nice_load);
+gov_attr_rw(powersave_bias);
+gov_attr_ro(min_sampling_rate);
+
+static struct attribute *od_attributes[] = {
+ &min_sampling_rate.attr,
+ &sampling_rate.attr,
+ &up_threshold.attr,
+ &sampling_down_factor.attr,
+ &ignore_nice_load.attr,
+ &powersave_bias.attr,
+ &io_is_busy.attr,
NULL
};
-static struct attribute_group od_attr_group_gov_sys = {
- .attrs = dbs_attributes_gov_sys,
- .name = "ondemand",
-};
-
-static struct attribute *dbs_attributes_gov_pol[] = {
- &min_sampling_rate_gov_pol.attr,
- &sampling_rate_gov_pol.attr,
- &up_threshold_gov_pol.attr,
- &sampling_down_factor_gov_pol.attr,
- &ignore_nice_load_gov_pol.attr,
- &powersave_bias_gov_pol.attr,
- &io_is_busy_gov_pol.attr,
- NULL
-};
-
-static struct attribute_group od_attr_group_gov_pol = {
- .attrs = dbs_attributes_gov_pol,
- .name = "ondemand",
-};
-
/************************** sysfs end ************************/
static int od_init(struct dbs_data *dbs_data, bool notify)
@@ -544,8 +523,7 @@ static struct dbs_governor od_dbs_gov = {
.owner = THIS_MODULE,
},
.governor = GOV_ONDEMAND,
- .attr_group_gov_sys = &od_attr_group_gov_sys,
- .attr_group_gov_pol = &od_attr_group_gov_pol,
+ .kobj_type = { .default_attrs = od_attributes },
.get_cpu_cdbs = get_cpu_cdbs,
.get_cpu_dbs_info_s = get_cpu_dbs_info_s,
.gov_dbs_timer = od_dbs_timer,