[PATCH] cpufreq: interactive: initialize cpufreq_global_kobject before using it - linaro-kernel

13 Feb 2014

Governors might use cpufreq_global_kobject when they don't have governor per
policy. And so they must initialize it with a call to
cpufreq_get_global_kobject(). Also after removing sysfs entries we must take the
refcount down as well with a call to: cpufreq_put_global_kobject().
If above isn't done we will see following boot crash:
kernel BUG at /home/arm/work/kernel/mywork/linux.git/fs/sysfs/group.c:92!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 3.14.0-rc1-00852-g293953e-dirty #171
task: ee094000 ti: ee092000 task.ti: ee092000
PC is at internal_create_group+0x1f0/0x224
LR is at cpufreq_governor_interactive+0x13c/0x504
pc : [<c01094a0>]    lr : [<c02aff44>]    psr: 60000113
sp : ee093c90  ip : 00013880  fp : ee301368
r10: ee301300  r9 : c05084f0  r8 : c0531814
r7 : 00000000  r6 : ee105640  r5 : ee301300  r4 : ee105640
r3 : c0531a88  r2 : c0531814  r1 : 00000000  r0 : 00000000
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: 10c5387d  Table: 4000406a  DAC: 00000015
<snip>
[<c01094a0>] (internal_create_group) from [<c02aff44>] (cpufreq_governor_interactive+0x13c/0x504)
[<c02aff44>] (cpufreq_governor_interactive) from [<c02ab090>] (__cpufreq_governor+0x78/0x1f0)
[<c02ab090>] (__cpufreq_governor) from [<c02ac224>] (cpufreq_set_policy+0x144/0x1c8)
[<c02ac224>] (cpufreq_set_policy) from [<c02ac530>] (cpufreq_init_policy+0x54/0x80)
[<c02ac530>] (cpufreq_init_policy) from [<c02ad8b0>] (__cpufreq_add_dev.isra.27+0x72c/0x804)
[<c02ad8b0>] (__cpufreq_add_dev.isra.27) from [<c0223610>] (subsys_interface_register+0x80/0xc4)
[<c0223610>] (subsys_interface_register) from [<c02ac890>] (cpufreq_register_driver+0xb8/0x214)
[<c02ac890>] (cpufreq_register_driver) from [<c02b0744>] (exynos_cpufreq_probe+0xf4/0x1a0)
[<c02b0744>] (exynos_cpufreq_probe) from [<c0225808>] (platform_drv_probe+0x18/0x48)
[<c0225808>] (platform_drv_probe) from [<c0224498>] (driver_probe_device+0x100/0x218)
[<c0224498>] (driver_probe_device) from [<c022463c>] (__driver_attach+0x8c/0x90)
[<c022463c>] (__driver_attach) from [<c0222cb8>] (bus_for_each_dev+0x54/0x88)
[<c0222cb8>] (bus_for_each_dev) from [<c0223c78>] (bus_add_driver+0xd4/0x1d0)
[<c0223c78>] (bus_add_driver) from [<c0224c58>] (driver_register+0x78/0xf4)
[<c0224c58>] (driver_register) from [<c0008854>] (do_one_initcall+0xe4/0x140)
[<c0008854>] (do_one_initcall) from [<c04c8c68>] (kernel_init_freeable+0xfc/0x1c8)
[<c04c8c68>] (kernel_init_freeable) from [<c0379abc>] (kernel_init+0x8/0x118)
[<c0379abc>] (kernel_init) from [<c000e5f8>] (ret_from_fork+0x14/0x3c)
Code: ebfc504c eaffffe0 e3500000 1affff8e (e7f001f2)
---[ end trace 04d313d9fc559575 ]---
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
---
Todd,
You need this patch for all kernels after 3.10. Not sure if android has already
hit 3.11 or not.. Though I haven't seena a branch for that :)
drivers/cpufreq/cpufreq_interactive.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c
index ff77b30..5286e57 100644
--- a/drivers/cpufreq/cpufreq_interactive.c
+++ b/drivers/cpufreq/cpufreq_interactive.c
@@ -1157,6 +1157,9 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy,
    	if (!have_governor_per_policy())
    		common_tunables = tunables;
+		if (!have_governor_per_policy())
+			WARN_ON(cpufreq_get_global_kobject());
+
    	rc = sysfs_create_group(get_governor_parent_kobj(policy),
    			get_sysfs_attr());
    	if (rc) {
@@ -1185,6 +1188,10 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy,
sysfs_remove_group(get_governor_parent_kobj(policy),
    				get_sysfs_attr());
+
+			if (!have_governor_per_policy())
+				cpufreq_put_global_kobject();
+
    		kfree(tunables);
    		common_tunables = NULL;
    	}
-- 
1.7.12.rc2.18.g61b472e



    