linux-kernel - Re: Regression on cpufreq in v3.12-rc1

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Message-ID: <CACRpkdZDqoqrEPfdra+iVS-hopLpJbPmWh=r8UkYRFUMg17jpw@mail.gmail.com>
Date:	Fri, 20 Sep 2013 17:21:04 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Viresh Kumar <viresh.kumar@...aro.org>
Cc:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Regression on cpufreq in v3.12-rc1

On Fri, Sep 20, 2013 at 10:49 AM, Viresh Kumar <viresh.kumar@...aro.org> wrote:

> We used to return early in case policy isn't found, but now we went
> and took the lock..

Aha!

> Hmm... Remember I told you last time that I have another way of fixing
> it up, probably we need that now..
>
> I wanted to add another variable to reflect if a cpufreq_driver is registered
> or not, and if not then return early from these routines..
>
> I will get that in now, please see if you can give it a try..

OK standing by.

> But I am still surprised how are we reaching this place before your cpufreq
> driver gets registered..

I have no idea really. The funny thing is that Russell has a similar
platform (Assabet) and he's not seeing the issue. It appears on this
h3600 iPAQ only.

So here is the backtrace:

[<c01db010>] (lock_policy_rwsem_read+0x0/0x3c) from [<c01dc6c8>]
(cpufreq_get+0x34/0x68)
[<c01dc694>] (cpufreq_get+0x0/0x68) from [<c01d2c94>]
(sa1100_pcmcia_set_timing+0x18/0x28)
 r5:00000000 r4:c182d008
[<c01d2c7c>] (sa1100_pcmcia_set_timing+0x0/0x28) from [<c01d27ec>]
(soc_pcmcia_add_one+0x100/0x220)
 r4:c182d008
[<c01d26ec>] (soc_pcmcia_add_one+0x0/0x220) from [<c01d2d30>]
(sa11xx_drv_pcmcia_add_one+0x8c/0xa4)
[<c01d2ca4>] (sa11xx_drv_pcmcia_add_one+0x0/0xa4) from [<c01d2de4>]
(sa11xx_drv_pcmcia_probe+0x9c/0xf8)
 r8:00000002 r7:c182d000 r6:c182d000 r5:00000000 r4:c182d008
[<c01d2d48>] (sa11xx_drv_pcmcia_probe+0x0/0xf8) from [<c01d3184>]
(pcmcia_h3600_init+0x1c/0x24)
[<c01d3168>] (pcmcia_h3600_init+0x0/0x24) from [<c01d2f70>]
(sa11x0_drv_pcmcia_probe+0x14/0x18)
[<c01d2f5c>] (sa11x0_drv_pcmcia_probe+0x0/0x18) from [<c019ec70>]
(platform_drv_probe+0x20/0x24)
[<c019ec50>] (platform_drv_probe+0x0/0x24) from [<c019d638>]
(really_probe+0x108/0x1c4)
[<c019d530>] (really_probe+0x0/0x1c4) from [<c019d724>]
(driver_probe_device+0x30/0x34)
 r8:00000000 r7:c019d970 r6:c05c81f0 r5:c05bb6b0 r4:c05bb67c
[<c019d6f4>] (driver_probe_device+0x0/0x34) from [<c019d9f8>]
(__driver_attach+0x88/0x8c)
[<c019d970>] (__driver_attach+0x0/0x8c) from [<c019bea0>]
(bus_for_each_dev+0x74/0x98)
 r6:c05c81f0 r5:c1833e40 r4:00000000
[<c019be2c>] (bus_for_each_dev+0x0/0x98) from [<c019d410>]
(driver_attach+0x20/0x28)
 r7:00000000 r6:c05c6c58 r5:c05c81f0 r4:c18c5900
[<c019d3f0>] (driver_attach+0x0/0x28) from [<c019cc6c>]
(bus_add_driver+0xe0/0x19c)
[<c019cb8c>] (bus_add_driver+0x0/0x19c) from [<c019dfe4>]
(driver_register+0x60/0x104)
 r7:c036b6ac r6:00000006 r5:00000000 r4:c05c81f0
[<c019df84>] (driver_register+0x0/0x104) from [<c019ef64>]
(__platform_driver_register+0x50/0x64)
 r5:00000000 r4:c1832000
[<c019ef14>] (__platform_driver_register+0x0/0x64) from [<c036b6c4>]
(sa11x0_pcmcia_init+0x18/0x20)
[<c036b6ac>] (sa11x0_pcmcia_init+0x0/0x20) from [<c00085a4>]
(do_one_initcall+0x9c/0xfc)
[<c0008508>] (do_one_initcall+0x0/0xfc) from [<c0355590>]
(do_initcall_level+0x80/0xb0)
 r7:c036fbec r6:00000006 r5:00000005 r4:c0372d9c
[<c0355510>] (do_initcall_level+0x0/0xb0) from [<c03555e4>]
(do_initcalls+0x24/0x30)
 r7:00000000 r6:00000000 r5:c0297820 r4:00000006
[<c03555c0>] (do_initcalls+0x0/0x30) from [<c03556bc>]
(do_basic_setup+0x28/0x2c)
 r4:00000000
[<c0355694>] (do_basic_setup+0x0/0x2c) from [<c0355a98>]
(kernel_init_freeable+0x4c/0xdc)
[<c0355a4c>] (kernel_init_freeable+0x0/0xdc) from [<c0297830>]
(kernel_init+0x10/0xf0)
 r4:00000000
[<c0297820>] (kernel_init+0x0/0xf0) from [<c000f950>] (ret_from_fork+0x14/0x24)
 r4:00000000
Code: e59f0014 eb02f800 e3a00000 e89da800 (e7f001f2)

sa11x0_pcmcia_init() which starts this chain of events is called as
an fs_initcall(), see drivers/pcmcia/sa1100_generic.c
if I comment out this one, I get the same thing in the frambuffer
driver instead, which is at module_init().

I don't have a trace so it's not like I know exactly what happened
before this point,
but the dmesg up to here reads:

Linux version 3.11.0-rc4-00024-g6eed940 (linus@...alhost.localdomain)
(gcc version 4.2.1) #41 Fri Sep 20 10:50:04 CEST 2013
CPU: StrongARM-1110 [6901b118] revision 8 (ARMv4), cr=c000717f
CPU: VIVT data cache, VIVT instruction cache
Machine: Compaq iPAQ H3600
Ignoring tag cmdline (using the default kernel command line)
Memory policy: ECC disabled, Data cache writeback
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 8128
Kernel command line: console=ttySA0,115200n8
PID hash table entries: 128 (order: -3, 512 bytes)
Dentry cache hash table entries: 4096 (order: 2, 16384 bytes)
Inode-cache hash table entries: 2048 (order: 1, 8192 bytes)
Memory: 26412K/32768K available (2643K kernel code, 118K rwdata, 736K
rodata, 2411K init, 76K bss, 6356K reserved)
Virtual kernel memory layout:
    vector  : 0xffff0000 - 0xffff1000   (   4 kB)
    fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)
    vmalloc : 0xc2800000 - 0xff000000   ( 968 MB)
    lowmem  : 0xc0000000 - 0xc2000000   (  32 MB)
    modules : 0xbf000000 - 0xc0000000   (  16 MB)
      .text : 0xc0008000 - 0xc0354f18   (3380 kB)
      .init : 0xc0355000 - 0xc05affb4   (2412 kB)
      .data : 0xc05b0000 - 0xc05cd840   ( 119 kB)
       .bss : 0xc05cd840 - 0xc05e0a68   (  77 kB)
SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
NR_IRQS:16 nr_irqs:49 49
sched_clock: 32 bits at 3686kHz, resolution 271ns, wraps every 1165084ms
Console: colour dummy device 80x30
console [ttySA0] enabled
Calibrating delay loop... 136.60 BogoMIPS (lpj=683008)
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 512
CPU: Testing write buffer coherency: ok
Setting up static identity map for 0xc029a910 - 0xc029a968
NET: Registered protocol family 16
DMA: preallocated 256 KiB pool for atomic coherent allocations
bio: create slab <bio-0> at 0
Switched to clocksource oscr

Yours,
Linus Walleij
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