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Date:   Sun, 24 May 2020 07:01:35 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        elver@...gle.com, tglx@...utronix.de, paulmck@...nel.org,
        mingo@...nel.org, peterz@...radead.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and
 PTE tables

On 5/24/20 5:32 AM, Mike Rapoport wrote:
> On Thu, May 21, 2020 at 04:02:11PM -0700, Guenter Roeck wrote:
>> On 5/20/20 12:51 PM, Mike Rapoport wrote:
>>> On Wed, May 20, 2020 at 12:03:31PM -0700, Guenter Roeck wrote:
>>>> On 5/20/20 10:03 AM, Mike Rapoport wrote:
>>>>> On Mon, May 18, 2020 at 09:37:15AM +0100, Will Deacon wrote:
>>>>>> On Sat, May 16, 2020 at 05:07:50PM -0700, Guenter Roeck wrote:
>>>>>>> On Sat, May 16, 2020 at 05:00:50PM -0700, Guenter Roeck wrote:
>>>>>>>> On Mon, May 11, 2020 at 09:41:36PM +0100, Will Deacon wrote:
>>>>>>>>> Now that the page table allocator can free page table allocations
>>>>>>>>> smaller than PAGE_SIZE, reduce the size of the PMD and PTE allocations
>>>>>>>>> to avoid needlessly wasting memory.
>>>>>>>>>
>>>>>>>>> Cc: "David S. Miller" <davem@...emloft.net>
>>>>>>>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>>>>>>>> Signed-off-by: Will Deacon <will@...nel.org>
>>>>>>>>
>>>>>>>> Something in the sparc32 patches in linux-next causes all my sparc32 emulations
>>>>>>>> to crash. bisect points to this patch, but reverting it doesn't help, and neither
>>>>>>>> does reverting the rest of the series.
>>>>>>>>
>>>>>>> Actually, turns out I see the same pattern (lots of scheduling while atomic
>>>>>>> followed by 'killing interrupt handler' in cryptomgr_test) with several
>>>>>>> powerpc boot tests.  I am currently bisecting those crashes. I'll report
>>>>>>> the results here as well as soon as I have it.
>>>>>>
>>>>>> FWIW, I retested my sparc32 patches with PREEMPT=y and I don't see any
>>>>>> issues. However, linux-next is a different story, where I don't get very far
>>>>>> at all:
>>>>>>
>>>>>> BUG: Bad page state in process swapper  pfn:005b4
>>>>
>>>> With above patch applied on top of Ira's patch, I get:
>>>>
>>>> BUG: spinlock recursion on CPU#0, S01syslogd/139
>>>>  lock: 0xf5448350, .magic: dead4ead, .owner: S01syslogd/139, .owner_cpu: 0
>>>> CPU: 0 PID: 139 Comm: S01syslogd Not tainted 5.7.0-rc6-next-20200518-00002-gb178d2d56f29-dirty #1
>>>> [f0067a64 :
>>>> do_raw_spin_lock+0xa8/0xd8 ]
>>>> [f00d5034 :
>>>> copy_page_range+0x328/0x804 ]
>>>> [f0025be4 :
>>>> dup_mm+0x334/0x434 ]
>>>> [f0027124 :
>>>> copy_process+0x1224/0x12b0 ]
>>>> [f0027344 :
>>>> _do_fork+0x54/0x30c ]
>>>> [f0027670 :
>>>> do_fork+0x5c/0x6c ]
>>>> [f000de44 :
>>>> sparc_do_fork+0x18/0x38 ]
>>>> [f000b7f4 :
>>>> do_syscall+0x34/0x40 ]
>>>> [5010cd4c :
>>>> 0x5010cd4c ]
>>>>
>>>> Looks like yet another problem.
>>>
>>> I've checked the patch above on top of the mmots which already has Ira's
>>> patches and it booted fine. I've used sparc32_defconfig to build the
>>> kernel and qemu-system-sparc with default machine and CPU. 
>>>
>>
>> Try sparc32_defconfig+SMP.
>  
> I see a differernt problem, but this could be related:
> 
> INIT: version 2.86 booting
> rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> 	(detected by 0, t=5252 jiffies, g=-935, q=3)
> rcu: All QSes seen, last rcu_sched kthread activity 5252 (-68674--73926), jiffies_till_next_fqs=1, root ->qsmask 0x0
> rcu: rcu_sched kthread starved for 5252 jiffies! g-935 f0x2 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
> rcu: 	Unless rcu_sched kthread gets sufficient CPU time, OOM is now expected behavior.
> rcu: RCU grace-period kthread stack dump:
> rcu_sched       R  running task        0    10      2 0x00000000
> 
> I'm running a bit old debian [1] with qemu-img-sparc.
> 
> My bisect pointed at commit 8c8f3156dd40 ("sparc32: mm: Reduce
> allocation size for PMD and PTE tables"). The commit ID is valid for
> next-20200522.
> 
Here is what I currently get:

next-20200522:
	All builds/tests crash
next-20200522 plus upstream commit 0cfc8a8d70dc ("sparc32: fix page table traversal in srmmu_nocache_init()"):
	nosmp images (sparc32_defconfig) boot fine
	smp images (sparc32_defconfig+SMP) crash with "BUG: Bad page state"
next-20200522 plus 0cfc8a8d70dc plus memblock_add() from below:
	smp images crash with spinlock recursion as above
next-20200522 plus 0cfc8a8d70dc plus revert of 8c8f3156dd40:
	smp images crash with "BUG: Bad page state"
next-20200522 plus 0cfc8a8d70dc plus revert of 8c8f3156dd40 plus memblock_add():
	All builds/tests pass

This is with my root file system. I tried the debian image but I seem to be
missing some command line option needed to make it work.

Guenter

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