On Thu, Mar 14, 2024 at 01:28:40PM +0100, Marek Szyprowski wrote: > On 14.03.2024 09:39, Catalin Marinas wrote: > > On Wed, Mar 13, 2024 at 05:13:33PM +0000, Russell King wrote: > >> So, I wonder whether what you're seeing is a latent bug which is > >> being tickled by the presence of the CPU masks being off-stack > >> changing the kernel timing. > >> > >> I would suggest the printk debug approach may help here to see when > >> the OPPs are begun to be parsed, when they're created etc and their > >> timing relationship to being used. Given the suspicion, it's possible > >> that the mere addition of printk() may "fix" the problem, which again > >> would be another semi-useful data point. > > It might be an init order problem. Passing "initcall_debug" on the > > cmdline might help a bit. > > > > It would also be useful in dev_pm_opp_set_config(), in the WARN_ON > > block, to print opp_table->opp_list.next to get an idea whether it looks > > like a valid pointer or memory corruption. > > I've finally found some time to do the step-by-step printk-based > debugging of this issue and finally found what's broken! > > Here is the fix: > > diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c > index 8bd6e5e8f121..2d83bbc65dd0 100644 > --- a/drivers/cpufreq/cpufreq-dt.c > +++ b/drivers/cpufreq/cpufreq-dt.c > @@ -208,7 +208,7 @@ static int dt_cpufreq_early_init(struct device *dev, > int cpu) > if (!priv) > return -ENOMEM; > > - if (!alloc_cpumask_var(&priv->cpus, GFP_KERNEL)) > + if (!zalloc_cpumask_var(&priv->cpus, GFP_KERNEL)) > return -ENOMEM; > > cpumask_set_cpu(cpu, priv->cpus); > > > It is really surprising that this didn't blow up for anyone else so > far... This means that the $subject patch is fine. > > I will send a proper patch fixing this issue in a few minutes. Nice. Many thanks for tracking this down. I'll revert the revert of the CPUMASK_OFFSTACK in the second part of the merging window (I already sent the pull request). -- Catalin
