Messages in this thread | | | Date | Thu, 26 Oct 2023 09:55:39 +0800 | Subject | Re: [PATCH 3/3] cpufreq: CPPC: Eliminate the impact of cpc_read() latency error | From | Zeng Heng <> |
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在 2023/10/25 19:01, Mark Rutland 写道: > On Wed, Oct 25, 2023 at 05:38:47PM +0800, Zeng Heng wrote: > > The previous patch added this function, and calls it with smp_call_on_cpu(), > where it'll run in IRQ context with IRQs disabled...
smp_call_on_cpu() puts the work to the bind-cpu worker.
And this function will be called in task context, and IRQs is certainly enabled.
Zeng Heng
>> struct fb_ctr_pair *fb_ctrs = val; >> int cpu = fb_ctrs->cpu; >> int ret; >> + unsigned long timeout; >> >> ret = cppc_get_perf_ctrs(cpu, &fb_ctrs->fb_ctrs_t0); >> if (ret) >> return ret; >> >> - udelay(2); /* 2usec delay between sampling */ >> + if (likely(!irqs_disabled())) { >> + /* >> + * Set 1ms as sampling interval, but never schedule >> + * to the idle task to prevent the AMU counters from >> + * stopping working. >> + */ >> + timeout = jiffies + msecs_to_jiffies(1); >> + while (!time_after(jiffies, timeout)) >> + cond_resched(); >> + >> + } else { > ... so we'll enter this branch of the if-else ... > >> + pr_warn_once("CPU%d: Get rate in atomic context", cpu); > ... and pr_warn_once() for something that's apparently normal and outside of > the user's control? > > That doesn't make much sense to me. > > Mark. > >> + udelay(2); /* 2usec delay between sampling */ >> + } >> >> return cppc_get_perf_ctrs(cpu, &fb_ctrs->fb_ctrs_t1); >> } >> -- >> 2.25.1 >>
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