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ba1ca654f3
linux_dsm_epyc7002/drivers/cpufreq
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Rafael J. Wysocki ba1ca654f3 cpufreq: governor: Fix prev_load initialization in cpufreq_governor_start() 
The way cpufreq_governor_start() initializes j_cdbs->prev_load is
questionable.

First off, j_cdbs->prev_cpu_wall used as a denominator in the
computation may be zero.  The case this happens is when
get_cpu_idle_time_us() returns -1 and get_cpu_idle_time_jiffy()
used to return that number is called exactly at the jiffies_64
wrap time.  It is rather hard to trigger that error, but it is not
impossible and it will just crash the kernel then.

Second, j_cdbs->prev_load is computed as the average load during
the entire time since the system started and it may not reflect the
load in the previous sampling period (as it is expected to).
That doesn't play well with the way dbs_update() uses that value.
Namely, if the update time delta (wall_time) happens do be greater
than twice the sampling rate on the first invocation of it, the
initial value of j_cdbs->prev_load (which may be completely off) will
be returned to the caller as the current load (unless it is equal to
zero and unless another CPU sharing the same policy object has a
greater load value).

For this reason, notice that the prev_load field of struct cpu_dbs_info
is only used by dbs_update() and only in that one place, so if
cpufreq_governor_start() is modified to always initialize it to 0,
it will make dbs_update() always compute the actual load first time
it checks the update time delta against the doubled sampling rate
(after initialization) and there won't be any side effects of it.

Consequently, modify cpufreq_governor_start() as described.

Fixes: 18b46abd00 (cpufreq: governor: Be friendly towards latency-sensitive bursty workloads)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
2016-04-25 16:21:34 +02:00
..
acpi-cpufreq.c cpufreq: ACPI: Remove freq_table from acpi_cpufreq_data 2016-04-09 01:54:31 +02:00
amd_freq_sensitivity.c cpufreq: governor: Make governor private data per-policy 2016-03-09 14:41:08 +01:00
arm_big_little_dt.c PM / OPP: Prefix exported opp routines with dev_pm_opp_ 2015-09-15 02:03:16 +02:00
arm_big_little.c cpufreq: arm_big_little: Add support to register a cpufreq cooling device 2015-12-10 00:14:58 +01:00
arm_big_little.h PM / OPP: Prefix exported opp routines with dev_pm_opp_ 2015-09-15 02:03:16 +02:00
at32ap-cpufreq.c cpufreq: at32ap: don't declare local variable as static 2014-04-07 14:31:33 +02:00
blackfin-cpufreq.c blackfin-cpufreq: Mark cpu_set_cclk() as static 2015-12-28 01:51:36 +01:00
cppc_cpufreq.c cpufreq: ACPI / CPPC: Add module support for cppc_cpufreq driver 2016-04-25 15:59:35 +02:00
cpufreq_conservative.c cpufreq: governor: New data type for management part of dbs_data 2016-04-02 01:09:00 +02:00
cpufreq_governor_attr_set.c cpufreq: governor: Move abstract gov_attr_set code to seperate file 2016-04-02 01:09:01 +02:00
cpufreq_governor.c cpufreq: governor: Fix prev_load initialization in cpufreq_governor_start() 2016-04-25 16:21:34 +02:00
cpufreq_governor.h cpufreq: Move governor symbols to cpufreq.h 2016-04-02 01:09:02 +02:00
cpufreq_ondemand.c cpufreq: governor: New data type for management part of dbs_data 2016-04-02 01:09:00 +02:00
cpufreq_ondemand.h cpufreq: governor: Relocate definitions of tuners structures 2016-03-09 14:41:09 +01:00
cpufreq_performance.c cpufreq: Clean up default and fallback governor setup 2016-02-05 02:37:42 +01:00
cpufreq_powersave.c cpufreq: Clean up default and fallback governor setup 2016-02-05 02:37:42 +01:00
cpufreq_stats.c cpufreq: stats: drop unnecessary locking 2015-01-23 23:06:45 +01:00
cpufreq_userspace.c cpufreq: Clean up default and fallback governor setup 2016-02-05 02:37:42 +01:00
cpufreq-dt-platdev.c cpufreq: hisilicon: Use generic platdev driver 2016-04-25 16:18:24 +02:00
cpufreq-dt.c cpufreq: dt: Drop stale comment 2016-04-05 03:40:44 +02:00
cpufreq-nforce2.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
cpufreq.c Merge back cpufreq changes for v4.7. 2016-04-25 15:44:01 +02:00
cris-artpec3-cpufreq.c cpufreq: create another field .flags in cpufreq_frequency_table 2014-04-07 14:43:50 +02:00
cris-etraxfs-cpufreq.c cpufreq: create another field .flags in cpufreq_frequency_table 2014-04-07 14:43:50 +02:00
davinci-cpufreq.c cpufreq: drop owner assignment from platform_drivers 2014-10-20 16:20:24 +02:00
dbx500-cpufreq.c cpufreq: drop owner assignment from platform_drivers 2014-10-20 16:20:24 +02:00
e_powersaver.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
elanfreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
exynos5440-cpufreq.c PM / OPP: Prefix exported opp routines with dev_pm_opp_ 2015-09-15 02:03:16 +02:00
freq_table.c cpufreq: Allow drivers to enable boost support after registering driver 2015-08-07 03:25:23 +02:00
gx-suspmod.c cpufreq: gx-suspmod: Fix two typos in two comments 2015-06-15 15:46:15 +02:00
highbank-cpufreq.c Merge branch 'mailbox-for-linus' of git://git.linaro.org/landing-teams/working/fujitsu/integration 2014-10-21 11:21:19 -07:00
ia64-acpi-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
imx6q-cpufreq.c Merge branch 'pm-opp' 2015-11-02 00:54:37 +01:00
integrator-cpufreq.c cpufreq: integrator: Fix module autoload for OF platform driver 2015-09-25 23:29:35 +02:00
intel_pstate.c cpufreq: intel_pstate: Use average P-State instead of current P-State 2016-04-25 15:45:11 +02:00
Kconfig cpufreq: dt: Add generic platform-device creation support 2016-04-09 01:18:42 +02:00
Kconfig.arm cpufreq: hisilicon: Use generic platdev driver 2016-04-25 16:18:24 +02:00
Kconfig.powerpc cpufreq: qoriq: rename the driver 2015-03-18 22:35:16 +01:00
Kconfig.x86 Revert "cpufreq: intel_pstate: Use ACPI perf configuration" 2015-11-19 00:20:42 +01:00
kirkwood-cpufreq.c cpufreq: drop owner assignment from platform_drivers 2014-10-20 16:20:24 +02:00
longhaul.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
longhaul.h cpufreq: delete __cpuinit usage from all cpufreq files 2013-07-14 19:36:57 -04:00
longrun.c cpufreq: add new routine cpufreq_verify_within_cpu_limits() 2013-10-16 00:50:23 +02:00
loongson2_cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
ls1x-cpufreq.c MIPS: Loongson: Naming style cleanup and rework 2015-06-21 21:53:59 +02:00
Makefile cpufreq: hisilicon: Use generic platdev driver 2016-04-25 16:18:24 +02:00
maple-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
mt8173-cpufreq.c cpufreq: mt8173: use list_for_each_entry*() 2016-04-09 01:27:54 +02:00
omap-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
p4-clockmod.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
pasemi-cpufreq.c cpufreq: Use cpufreq_for_each_* macros for frequency table iteration 2014-04-30 00:06:21 +02:00
pcc-cpufreq.c cpufreq: pcc-cpufreq: update default value of cpuinfo_transition_latency 2015-12-10 00:17:03 +01:00
pmac32-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
pmac64-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
powernow-k6.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
powernow-k7.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
powernow-k7.h [CPUFREQ] Move x86 drivers to drivers/cpufreq/ 2011-05-19 18:51:07 -04:00
powernow-k8.c ACPI / processor: Drop an unused argument of a cleanup routine 2015-07-22 22:11:16 +02:00
powernow-k8.h cpufreq: powernow-k8: Suppress checkpatch warnings 2014-05-17 01:27:01 +02:00
powernv-cpufreq.c cpufreq: powernv: Add sysfs attributes to show throttle stats 2016-03-22 23:11:18 +01:00
ppc_cbe_cpufreq_pervasive.c cpufreq: powerpc/platforms/cell: move cpufreq driver to drivers/cpufreq 2013-04-10 13:19:26 +02:00
ppc_cbe_cpufreq_pmi.c cpufreq: ppc_cbe_cpufreq_pmi: make the driver explicitly non-modular 2016-04-09 01:11:04 +02:00
ppc_cbe_cpufreq.c cpufreq: Use cpufreq_for_each_* macros for frequency table iteration 2014-04-30 00:06:21 +02:00
ppc_cbe_cpufreq.h cpufreq: powerpc/platforms/cell: move cpufreq driver to drivers/cpufreq 2013-04-10 13:19:26 +02:00
pxa2xx-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
pxa3xx-cpufreq.c cpufreq: Remove cpufreq_generic_exit() 2014-03-12 01:06:00 +01:00
qoriq-cpufreq.c cpufreq: qoriq: Fix cooling device registration issue during suspend 2016-04-25 16:07:02 +02:00
s3c24xx-cpufreq-debugfs.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
s3c24xx-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
s3c64xx-cpufreq.c cpufreq: Use cpufreq_for_each_* macros for frequency table iteration 2014-04-30 00:06:21 +02:00
s3c2410-cpufreq.c cpufreq: s3c24xx: Remove some dead code 2014-07-19 04:24:59 +09:00
s3c2412-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
s3c2416-cpufreq.c cpufreq: s3c: remove incorrect __init annotations 2015-02-19 06:36:53 +01:00
s3c2440-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
s5pv210-cpufreq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
sa1100-cpufreq.c cpufreq: Mark ARM drivers with CPUFREQ_NEED_INITIAL_FREQ_CHECK flag 2014-01-06 14:17:25 +01:00
sa1110-cpufreq.c cpufreq: sa1110: set memory type for h3600 2014-07-16 14:30:17 +02:00
sc520_freq.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
scpi-cpufreq.c cpufreq: scpi-cpufreq: signedness bug in scpi_get_dvfs_info() 2015-12-24 02:11:37 +01:00
sfi-cpufreq.c cpufreq: sfi: use kmemdup rather than duplicating its implementation 2015-09-01 15:51:15 +02:00
sh-cpufreq.c cpufreq: Convert existing drivers to use cpufreq_freq_transition_{begin|end} 2014-03-26 16:41:41 +01:00
sparc-us2e-cpufreq.c cpufreq: add 'freq_table' in struct cpufreq_policy 2014-03-12 01:06:00 +01:00
sparc-us3-cpufreq.c cpufreq: add 'freq_table' in struct cpufreq_policy 2014-03-12 01:06:00 +01:00
spear-cpufreq.c cpufreq: drop owner assignment from platform_drivers 2014-10-20 16:20:24 +02:00
speedstep-centrino.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
speedstep-ich.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
speedstep-lib.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
speedstep-lib.h [CPUFREQ] Move x86 drivers to drivers/cpufreq/ 2011-05-19 18:51:07 -04:00
speedstep-smi.c cpufreq: Use consistent prefixing via pr_fmt 2016-04-09 01:35:18 +02:00
sti-cpufreq.c cpufreq: st: Provide runtime initialised driver for ST's platforms 2015-12-12 02:55:21 +01:00
tegra20-cpufreq.c cpufreq: tegra20: remove superfluous CONFIG_PM ifdefs 2015-09-26 03:00:57 +02:00
tegra124-cpufreq.c cpufreq: tegra124: No need of setting platform-data 2016-04-09 01:12:09 +02:00
unicore2-cpufreq.c cpufreq: unicore32: replace IS_ERR and PTR_ERR with PTR_ERR_OR_ZERO 2014-04-21 23:42:27 +02:00
vexpress-spc-cpufreq.c cpufreq: drop owner assignment from platform_drivers 2014-10-20 16:20:24 +02:00