On Monday, November 26, 2012 07:10:12 PM Fabio Baltieri wrote:
> Fix cpufreq_gov_ondemand to skip CPU where another governor is used.
>
> The bug present itself as NULL pointer access on the mutex_lock() call,
> an can be reproduced on an SMP machine by setting the default governor
> to anything other than ondemand, setting a single CPU's governor to
> ondemand, then changing the sample rate by writing on:
>
> > /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate
>
> Backtrace:
>
> Nov 26 17:36:54 balto kernel: [ 839.585241] BUG: unable to handle kernel
> NULL pointer dereference at (null)
> Nov 26 17:36:54 balto kernel: [ 839.585311] IP: [<ffffffff8174e082>]
> __mutex_lock_slowpath+0xb2/0x170
> [snip]
> Nov 26 17:36:54 balto kernel: [ 839.587005] Call Trace:
> Nov 26 17:36:54 balto kernel: [ 839.587030] [<ffffffff8174da82>]
> mutex_lock+0x22/0x40
> Nov 26 17:36:54 balto kernel: [ 839.587067] [<ffffffff81610b8f>]
> store_sampling_rate+0xbf/0x150
> Nov 26 17:36:54 balto kernel: [ 839.587110] [<ffffffff81031e9c>] ?
> __do_page_fault+0x1cc/0x4c0
> Nov 26 17:36:54 balto kernel: [ 839.587153] [<ffffffff813309bf>]
> kobj_attr_store+0xf/0x20
> Nov 26 17:36:54 balto kernel: [ 839.587192] [<ffffffff811bb62d>]
> sysfs_write_file+0xcd/0x140
> Nov 26 17:36:54 balto kernel: [ 839.587234] [<ffffffff8114c12c>]
> vfs_write+0xac/0x180
> Nov 26 17:36:54 balto kernel: [ 839.587271] [<ffffffff8114c472>]
> sys_write+0x52/0xa0
> Nov 26 17:36:54 balto kernel: [ 839.587306] [<ffffffff810321ce>] ?
> do_page_fault+0xe/0x10
> Nov 26 17:36:54 balto kernel: [ 839.587345] [<ffffffff81751202>]
> system_call_fastpath+0x16/0x1b
>
> Signed-off-by: Fabio Baltieri <fabio.balti...@linaro.org>
> ---
>
> Hi Rafael,
>
> this is based on a clean linux-pm linux-next branch (i.e. not with my other
> patch-set applied), so expect a context conflict if both are applied.
I have applied this patch to my linux-next branch.
As for the other series, I'm in the process of reviewing it, but I rather
won't include it into my first pull request for v3.8.
Thanks,
Rafael
> drivers/cpufreq/cpufreq_ondemand.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq_ondemand.c
> b/drivers/cpufreq/cpufreq_ondemand.c
> index cca3e9f..7731f7c 100644
> --- a/drivers/cpufreq/cpufreq_ondemand.c
> +++ b/drivers/cpufreq/cpufreq_ondemand.c
> @@ -40,6 +40,10 @@
> static struct dbs_data od_dbs_data;
> static DEFINE_PER_CPU(struct od_cpu_dbs_info_s, od_cpu_dbs_info);
>
> +#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND
> +static struct cpufreq_governor cpufreq_gov_ondemand;
> +#endif
> +
> static struct od_dbs_tuners od_tuners = {
> .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
> .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
> @@ -279,6 +283,10 @@ static void update_sampling_rate(unsigned int new_rate)
> policy = cpufreq_cpu_get(cpu);
> if (!policy)
> continue;
> + if (policy->governor != &cpufreq_gov_ondemand) {
> + cpufreq_cpu_put(policy);
> + continue;
> + }
> dbs_info = &per_cpu(od_cpu_dbs_info, policy->cpu);
> cpufreq_cpu_put(policy);
>
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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