Messages in this thread Patch in this message | | | From | Tomeu Vizoso <> | Subject | [PATCH 2/2] cpufreq: Guard against not-yet-initialized policies in cpufreq_cpu_get | Date | Tue, 28 Oct 2014 16:26:48 +0100 |
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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@collabora.com> --- 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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