[PATCH 2/2] cpufreq: Guard against not-yet-initialized policies in cpufreq_cpu_get
From: Tomeu Vizoso
Date: Tue Oct 28 2014 - 11:27:33 EST
There's a substantial window of opportunity from the time the policy objects
are created until they are initialized, causing this:
[ 4.651435] ------------[ cut here ]------------
[ 4.651453] WARNING: CPU: 1 PID: 64 at include/linux/kref.h:47 kobject_get+0x64/0x70()
[ 4.651463] Modules linked in:
[ 4.651473] CPU: 1 PID: 64 Comm: irq/77-tegra-ac Not tainted 3.18.0-rc1-next-20141027ccu-00049-g21a0041 #248
[ 4.651497] [<c0016fac>] (unwind_backtrace) from [<c001272c>] (show_stack+0x10/0x14)
[ 4.651505] [<c001272c>] (show_stack) from [<c0601920>] (dump_stack+0x98/0xd8)
[ 4.651515] [<c0601920>] (dump_stack) from [<c00288d8>] (warn_slowpath_common+0x70/0x8c)
[ 4.651522] [<c00288d8>] (warn_slowpath_common) from [<c0028990>] (warn_slowpath_null+0x1c/0x24)
[ 4.651530] [<c0028990>] (warn_slowpath_null) from [<c02227bc>] (kobject_get+0x64/0x70)
[ 4.651539] [<c02227bc>] (kobject_get) from [<c03e5238>] (cpufreq_cpu_get+0x88/0xc8)
[ 4.651547] [<c03e5238>] (cpufreq_cpu_get) from [<c03e52ec>] (cpufreq_get+0xc/0x64)
[ 4.651555] [<c03e52ec>] (cpufreq_get) from [<c0287818>] (actmon_thread_isr+0x140/0x1a4)
[ 4.651563] [<c0287818>] (actmon_thread_isr) from [<c0068a68>] (irq_thread_fn+0x1c/0x40)
[ 4.651570] [<c0068a68>] (irq_thread_fn) from [<c0068d84>] (irq_thread+0x134/0x174)
[ 4.651579] [<c0068d84>] (irq_thread) from [<c0040284>] (kthread+0xdc/0xf4)
[ 4.651587] [<c0040284>] (kthread) from [<c000f4b8>] (ret_from_fork+0x14/0x3c)
[ 4.651591] ---[ end trace 7f6a15d1272e6ef3 ]---
This commit checks that the policy object has been initialized already before
trying to ref it.
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
---
drivers/cpufreq/cpufreq.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 644b54e..37cd6c9 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -214,8 +214,12 @@ struct cpufreq_policy *cpufreq_cpu_get(unsigned int cpu)
if (cpufreq_driver) {
/* get the CPU */
policy = per_cpu(cpufreq_cpu_data, cpu);
- if (policy)
- kobject_get(&policy->kobj);
+ if (policy) {
+ if (!kobject_initialized(&policy->kobj))
+ policy = NULL;
+ else
+ kobject_get(&policy->kobj);
+ }
}
read_unlock_irqrestore(&cpufreq_driver_lock, flags);
--
1.9.3
--
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