linux-kernel - Re: sparc boot failure due to perf init

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Date:	Fri, 7 Jan 2011 21:22:21 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	David Miller <davem@...emloft.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	sparclinux <sparclinux@...r.kernel.org>
Subject: Re: sparc boot failure due to perf init

On Fri, Jan 07, 2011 at 09:18:05PM +0100, Sam Ravnborg wrote:
> I have upgraded my Sun Blade 100 to latest mainline,
> and when it booted I hit an oops.
> 
> Relevant bits from the oops:
> Mount-cache hash table entries: 512
> Performance events: perf (null)    <<<<<<<<<<<<<<<<<<<
> Unable to handle kernel NULL pointer dereference
> tsk->{mm,active_mm}->context = 0000000000000000
> tsk->{mm,active_mm}->pgd = fffff800003e4634
>               \|/ ____ \|/
>               "@'/ .. \`@"
>               /_| \__/ |_\
>                  \__U_/
> swapper(1): Oops [#1]
> TSTATE: 0000004480001606 TPC: 000000000055c180 TNPC: 000000000055c184 Y: 00000000    Not tainted
> TPC: <strcmp+0x0/0x40>
> g0: fffff8000f03f800 g1: 00000000007df800 g2: 000000000078f918 g3: 0000000000799168
> g4: fffff8000f0358c0 g5: fffff80000c22000 g6: fffff8000f038000 g7: 0000000000000001
> o0: 0000000000000000 o1: 000000000073b050 o2: 0000000000000001 o3: 0000000000000001
> o4: fffff8000f0356c8 o5: 0000000000000000 sp: fffff8000f03b531 ret_pc: 00000000007b9e30
> RPC: <init_hw_perf_events+0x30/0x168>
> l0: 0000000000000000 l1: 00000000007e0a80 l2: 00000000007e2140 l3: 0000000000000001
> l4: 0000000000000000 l5: 0000000000000000 l6: 0000000000000000 l7: 0000000000777b78
> i0: fffff80001402a80 i1: 0000000000000000 i2: 0000000000000001 i3: 0000000000000001
> i4: 0000000000000000 i5: 0000000000000005 i6: fffff8000f03b5e1 i7: 00000000007b41c8
> I7: <do_one_initcall+0x68/0x140>
> 
> The line mared "<<<<<<<<<<<<<" is added by my printf debugging.
> It shows that sparc_pmu_type is NULL.
> 
> sparc_pmu_type is set in cpu_type_probe(void) which is:
> 
>    arch_initcall(cpu_type_probe);
> 
> But init_hw_perf_events() is:
> 
>    early_initcall(init_hw_perf_events);
> 
> So we end up calling init_hw_perf_events() before we call cpu_type_probe(),
> and sparc_pmu_type is not set.
> 
> This was introduced by: 
> "perf, arch: Cleanup perf-pmu init vs lockup-detector" - 004417a6d468e24399e383645c068b498eed84ad
Note: I did not try a revert or anything.
I just looked at the patch and concluded this was the culprint.

	Sam
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