Re: [patch] voluntary-preempt-2.6.9-rc2-mm4-S7

[Ingo Molnar]

* Lee Revell <rlrevell@xxxxxxxxxxx> wrote:

> This one was caused by amlat:
> 
> preemption latency trace v1.0.7 on 2.6.9-rc2-mm4-VP-S7
> -------------------------------------------------------
>  latency: 264 us, entries: 5 (5)   |   [VP:1 KP:1 SP:1 HP:1 #CPUS:1]
>     -----------------
>     | task: amlat/3921, uid:1000 nice:0 policy:1 rt_prio:99
>     -----------------
>  => started at: rtc_open+0x12/0x270
>  => ended at:   rtc_open+0x13f/0x270
> =======>
> 00000001 0.000ms (+0.264ms): rtc_open (misc_open)
> 00000001 0.264ms (+0.000ms): sub_preempt_count (rtc_open)
> 00000001 0.265ms (+0.000ms): update_max_trace (check_preempt_timing)
> 00000001 0.265ms (+0.000ms): _mmx_memcpy (update_max_trace)
> 00000001 0.265ms (+0.000ms): kernel_fpu_begin (_mmx_memcpy)

weird, there's nothing in that function that should cause _any_ delay.
Is this drivers/char/rtc.c's rtc_open()? Also, how reproducible is this
delay?

	Ingo
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