Re: [PATCH 0/3] cpufreq: governor: Fix potential races

[Viresh Kumar <viresh.kumar@linaro.org>]

On 04-06-15, 11:38, Preeti U Murthy wrote:
> And a crash at the cpufreq worker thread again due to data access
> exception when I change governors in parallel on a single core.
> 
> cpu 0x3: Vector: 300 (Data Access) at [c000000fedb538f0]
>     pc: c000000000856750: od_dbs_timer+0x60/0x1e0
>     lr: c0000000000f489c: process_one_work+0x24c/0x910
>     sp: c000000fedb53b70
>    msr: 9000000100009033
>    dar: 10
>  dsisr: 40000000
>   current = 0xc000000fe3d128e0
>   paca    = 0xc000000007da1c80	 softe: 0	 irq_happened: 0x01
>     pid   = 17227, comm = kworker/3:1
> 
> With the backtrace being:
> 
> [c000000fedb53be0] c0000000000f489c process_one_work+0x24c/0x910
> [c000000fedb53c90] c0000000000f50dc worker_thread+0x17c/0x540
> [c000000fedb53d20] c0000000000fed70 kthread+0x120/0x140
> [c000000fedb53e30] c000000000009678 ret_from_kernel_thread+0x5c/0x64
> 
> But the kernel stays sane longer than before with the patchset. The
> above crash happens around 15 seconds after the test begins, while
> earlier it wouldn't survive 2 seconds even.

I haven't attempted to solve the race between the worker threads and
governor-callbacks yet. What I have tried to solve is the race between
different callbacks. And you shouldn't see a race there for now. For
example a race between INIT/EXIT/START/STOP/LIMITS.

-- 
viresh