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Viresh Kumar 32e1ac30b6 cpufreq: Register drivers only after CPU devices have been registered
[ Upstream commit 46770be0cf ]

The cpufreq core heavily depends on the availability of the struct
device for CPUs and if they aren't available at the time cpufreq driver
is registered, we will never succeed in making cpufreq work.

This happens due to following sequence of events:

- cpufreq_register_driver()
  - subsys_interface_register()
  - return 0; //successful registration of driver

... at a later point of time

- register_cpu();
  - device_register();
    - bus_probe_device();
      - sif->add_dev();
	- cpufreq_add_dev();
	  - get_cpu_device(); //FAILS
  - per_cpu(cpu_sys_devices, num) = &cpu->dev; //used by get_cpu_device()
  - return 0; //CPU registered successfully

Because the per-cpu variable cpu_sys_devices is set only after the CPU
device is regsitered, cpufreq will never be able to get it when
cpufreq_add_dev() is called.

This patch avoids this failure by making sure device structure of at
least CPU0 is available when the cpufreq driver is registered, else
return -EPROBE_DEFER.

Reported-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Co-developed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2019-12-31 16:45:26 +01:00
Documentation USB: documentation: flags on usb-storage versus UAS 2019-12-17 19:55:32 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch s390/disassembler: don't hide instruction addresses 2019-12-31 16:45:23 +01:00
block block: fix "check bi_size overflow before merge" 2019-12-21 11:04:32 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: aegis128/simd - build 32-bit ARM for v8 architecture explicitly 2019-12-31 16:43:57 +01:00
drivers cpufreq: Register drivers only after CPU devices have been registered 2019-12-31 16:45:26 +01:00
fs Btrfs: fix removal logic of the tree mod log that leads to use-after-free issues 2019-12-31 16:42:07 +01:00
include net: avoid potential false sharing in neighbor related code 2019-12-31 16:45:03 +01:00
init Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
ipc ipc/sem.c: convert to use built-in RCU list checking 2019-09-25 17:51:41 -07:00
kernel cgroup: freezer: don't change task and cgroups status unnecessarily 2019-12-31 16:45:06 +01:00
lib ubsan, x86: Annotate and allow __ubsan_handle_shift_out_of_bounds() in uaccess regions 2019-12-31 16:44:25 +01:00
mm mm/shmem.c: cast the type of unmap_start to u64 2019-12-17 19:56:51 +01:00
net Bluetooth: Fix advertising duplicated flags 2019-12-31 16:44:33 +01:00
samples samples: pktgen: fix proc_cmd command result check logic 2019-12-31 16:43:45 +01:00
scripts arm64 fix for -rc8 / final 2019-11-15 09:14:23 -08:00
security efi/efi_test: Lock down /dev/efi_test and require CAP_SYS_ADMIN 2019-10-31 09:40:21 +01:00
sound ASoC: Intel: kbl_rt5663_rt5514_max98927: Add dmic format constraint 2019-12-31 16:45:21 +01:00
tools bpf, testing: Workaround a verifier failure for test_progs 2019-12-31 16:45:20 +01:00
usr kbuild: update compile-test header list for v5.4-rc2 2019-10-05 15:29:49 +09:00
virt KVM: arm/arm64: vgic: Don't rely on the wrong pending table 2019-12-13 08:43:00 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-22 14:28:14 -08:00
Makefile Linux 5.4.6 2019-12-21 11:05:23 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.