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Date:   Sat, 16 May 2020 17:07:50 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Will Deacon <will@kernel.org>
Cc:     linux-kernel@vger.kernel.org, elver@google.com, tglx@linutronix.de,
        paulmck@kernel.org, mingo@kernel.org, peterz@infradead.org,
        "David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH v5 04/18] sparc32: mm: Reduce allocation size for PMD and
 PTE tables
Message-ID: <20200517000750.GA157503@roeck-us.net>
References: <20200511204150.27858-1-will@kernel.org>
 <20200511204150.27858-5-will@kernel.org>
 <20200517000050.GA87467@roeck-us.net>
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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@davemloft.net>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Signed-off-by: Will Deacon <will@kernel.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.

Guenter

> Guenter
> 
> ---
> Bisect log:
> 
> # bad: [bdecf38f228bcca73b31ada98b5b7ba1215eb9c9] Add linux-next specific files for 20200515
> # good: [2ef96a5bb12be62ef75b5828c0aab838ebb29cb8] Linux 5.7-rc5
> git bisect start 'HEAD' 'v5.7-rc5'
> # bad: [3674d7aa7a8e61d993886c2fb7c896c5ef85e988] Merge remote-tracking branch 'crypto/master'
> git bisect bad 3674d7aa7a8e61d993886c2fb7c896c5ef85e988
> # bad: [1ab4d6ff0a3ee4b29441d8b0076bc8d4734bd16e] Merge remote-tracking branch 'hwmon-staging/hwmon-next'
> git bisect bad 1ab4d6ff0a3ee4b29441d8b0076bc8d4734bd16e
> # good: [dccfae3ab84387c94f2efc574d41efae005eeee5] Merge remote-tracking branch 'tegra/for-next'
> git bisect good dccfae3ab84387c94f2efc574d41efae005eeee5
> # bad: [20f9d1287c9f0047b81497197c9f4893485bbe15] Merge remote-tracking branch 'djw-vfs/vfs-for-next'
> git bisect bad 20f9d1287c9f0047b81497197c9f4893485bbe15
> # bad: [6537897637b5b91f921cb0ac6c465a593f4a665e] Merge remote-tracking branch 'sparc-next/master'
> git bisect bad 6537897637b5b91f921cb0ac6c465a593f4a665e
> # good: [bca1583e0693e0ba76450b684c5910f7083eeef4] Merge remote-tracking branch 'mips/mips-next'
> git bisect good bca1583e0693e0ba76450b684c5910f7083eeef4
> # good: [1f12096aca212af8fad3ef58d5673cde691a1452] Merge the lockless page table walk rework into next
> git bisect good 1f12096aca212af8fad3ef58d5673cde691a1452
> # good: [23a457b8d57dc8d0cc1dbd1882993dd2fcc4b0c0] s390: nvme reipl
> git bisect good 23a457b8d57dc8d0cc1dbd1882993dd2fcc4b0c0
> # good: [f57f5010c0c3fe2d924a957ddf1d17fbebb54d47] Merge remote-tracking branch 'risc-v/for-next'
> git bisect good f57f5010c0c3fe2d924a957ddf1d17fbebb54d47
> # good: [1d5fd6c33b04e5d5b665446c3b56f2148f0f1272] sh: add missing DECLARE_EXPORT() for __ashiftrt_r4_xx
> git bisect good 1d5fd6c33b04e5d5b665446c3b56f2148f0f1272
> # bad: [8c8f3156dd40f8bdc58f2ac461374bc804c28e3b] sparc32: mm: Reduce allocation size for PMD and PTE tables
> git bisect bad 8c8f3156dd40f8bdc58f2ac461374bc804c28e3b
> # good: [8e958839e4b9fb6ea4385ff2c52d1333a3a618de] sparc32: mm: Restructure sparc32 MMU page-table layout
> git bisect good 8e958839e4b9fb6ea4385ff2c52d1333a3a618de
> # good: [3f407976ac2953116cb8880a7a18b63bcc81829d] sparc32: mm: Change pgtable_t type to pte_t * instead of struct page *
> git bisect good 3f407976ac2953116cb8880a7a18b63bcc81829d
> # first bad commit: [8c8f3156dd40f8bdc58f2ac461374bc804c28e3b] sparc32: mm: Reduce allocation size for PMD and PTE tables
> 
> ---
> Log messages:
> 
> Lots of:
> 
> BUG: scheduling while atomic: kthreadd/2/0xffffffff
> Modules linked in:
> CPU: 0 PID: 2 Comm: kthreadd Tainted: G        W         5.7.0-rc5-next-20200515 #1
> [f04f2c94 :
> here+0x16c/0x250 ]
> [f04f2df0 :
> schedule+0x78/0x11c ]
> [f003f100 :
> kthreadd+0x188/0x1a4 ]
> [f0008448 :
> ret_from_kernel_thread+0xc/0x38 ]
> [00000000 :
> 0x0 ]
> 
> followed by:
> 
> Kernel panic - not syncing: Aiee, killing interrupt handler!
> CPU: 0 PID: 19 Comm: cryptomgr_test Tainted: G        W         5.7.0-rc5-next-20200515 #1
> [f0024400 :
> do_exit+0x7c8/0xa88 ]
> [f0075540 :
> __module_put_and_exit+0xc/0x18 ]
> [f0221428 :
> cryptomgr_test+0x28/0x48 ]
> [f003edc0 :
> kthread+0xf4/0x12c ]
> [f0008448 :
> ret_from_kernel_thread+0xc/0x38 ]
> [00000000 :
> 0x0 ]