Messages in this thread | | | Date | Mon, 20 Jun 2011 16:55:43 +0530 | From | Santosh Shilimkar <> | Subject | Re: [RFC PATCH] ARM: smp: Fix the CPU hotplug race with scheduler. |
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On 6/20/2011 4:43 PM, Russell King - ARM Linux wrote: > On Mon, Jun 20, 2011 at 04:17:58PM +0530, Santosh Shilimkar wrote: >> Yes. It's because of interrupt and the CPU active-online >> race. > > I don't see that as a conclusion from this dump. > >> Here is the chash log.. >> [ 21.025451] CPU1: Booted secondary processor >> [ 21.025451] CPU1: Unknown IPI message 0x1 >> [ 21.029113] Switched to NOHz mode on CPU #1 >> [ 21.029174] BUG: spinlock lockup on CPU#1, swapper/0, c06220c4 > > That's the xtime seqlock. We're trying to update the xtime from CPU1, > which is not yet online and not yet active. That's fine, we're just > spinning on the spinlock here, waiting for the other CPUs to release > it. > > But what this is saying is that the other CPUs aren't releasing it. > The cpu hotplug code doesn't hold the seqlock either. So who else is > holding this lock, causing CPU1 to time out on it. > > The other thing is that this is only supposed to trigger after about > one second: > > u64 loops = loops_per_jiffy * HZ; > for (i = 0; i< loops; i++) { > if (arch_spin_trylock(&lock->raw_lock)) > return; > __delay(1); > } > > which from the timings you have at the beginning of your printk lines > is clearly not the case - it's more like 61us. > > Are you running with those h/w timer delay patches? Nope.
Regards Santosh
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