On Monday, May 29, 2017 02:18:52 AM Jongman Heo wrote:
>
> Hi,
>
> FYI, 4.12-rc3 still has this issue.
>
>
> --------- Original Message ---------
> Sender : 허종만 <[email protected]>
> Date : 2017-05-16 13:25 (GMT+9)
> Title : [4.12 regression] "cpufreq: intel_pstate: Active mode P-state limits
> rework"
>
>
> Hi,
>
> With 4.12-rc1 (Linus git), booting fails due to kernel panic, at
> intel_pstate_register_driver+0x56/0x110.
> I can't copy the whole trace from the graphic console, it looks like below.
>
> Call Trace:
> intel_pstate_init
> intel_pstate_setup
> do_one_initcall
> set_debug_rodata
> kernel_init_freeable
> rest_init
> kernel_init
> ret_from_fork
> Code: ...
> RIP: intel_pstate_register_driver+0x56/0x110 RSP: ffffa3a98000bd80
> ...
I guess this is a division by 0 due to the unmet assumption that the denominator
in min_perf_pct_min() will always be nonzero.
If this guess is correct, the patch below should help, so can you please test
it?
Thanks,
Rafael
---
drivers/cpufreq/intel_pstate.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -571,9 +571,10 @@ static inline void update_turbo_state(vo
static int min_perf_pct_min(void)
{
struct cpudata *cpu = all_cpu_data[0];
+ int turbo_pstate = cpu->pstate.turbo_pstate;
- return DIV_ROUND_UP(cpu->pstate.min_pstate * 100,
- cpu->pstate.turbo_pstate);
+ return turbo_pstate ?
+ DIV_ROUND_UP(cpu->pstate.min_pstate * 100, turbo_pstate) : 0;
}
static s16 intel_pstate_get_epb(struct cpudata *cpu_data)
