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Date: Tue, 21 Nov 2023 08:58:40 +0800
From: Chengming Zhou <chengming.zhou@...ux.dev>
To: Mark Brown <broonie@...nel.org>
Cc: vbabka@...e.cz, cl@...ux.com, penberg@...nel.org,
rientjes@...gle.com, iamjoonsoo.kim@....com,
akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
42.hyeyoo@...il.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [PATCH v5 6/9] slub: Delay freezing of partial slabs
On 2023/11/21 02:49, Mark Brown wrote:
> On Thu, Nov 02, 2023 at 03:23:27AM +0000, chengming.zhou@...ux.dev wrote:
>> From: Chengming Zhou <zhouchengming@...edance.com>
>>
>> Now we will freeze slabs when moving them out of node partial list to
>> cpu partial list, this method needs two cmpxchg_double operations:
>>
>> 1. freeze slab (acquire_slab()) under the node list_lock
>> 2. get_freelist() when pick used in ___slab_alloc()
>
> Recently -next has been failing to boot on a Raspberry Pi 3 with an arm
> multi_v7_defconfig and a NFS rootfs, a bisect appears to point to this
> patch (in -next as c8d312e039030edab25836a326bcaeb2a3d4db14) as having
> introduced the issue. I've included the full bisect log below.
>
> When we see problems we see RCU stalls while logging in, for example:
>
> debian-testing-armhf login: root (automatic login)
> Linux debian-testing-armhf 6.7.0-rc1-00006-gc8d312e03903 #1 SMP @1699864348 armv7l
> The programs included with the Debian GNU/Linux system are free software;
> the exact distribution terms for each program are described in the
> individual files in /usr/share/doc/*/copyright.
> Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
> permitted by applicable law.
> [ 46.453323] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [ 46.459361] rcu: 3-...0: (1 GPs behind) idle=def4/1/0x40000000 softirq=1304/1304 fqs=951
> [ 46.467669] rcu: (detected by 0, t=2103 jiffies, g=1161, q=499 ncpus=4)
> [ 46.474472] Sending NMI from CPU 0 to CPUs 3:
IIUC, here should print the backtrace of CPU 3, right? It looks like CPU 3 is the cause,
but we couldn't see what it's doing from the log.
Thanks!
> [ 56.478894] rcu: rcu_sched kthread timer wakeup didn't happen for 1002 jiffies! g1161 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
> [ 56.490195] rcu: Possible timer handling issue on cpu=0 timer-softirq=1650
> [ 56.497259] rcu: rcu_sched kthread starved for 1005 jiffies! g1161 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=0
> [ 56.507589] rcu: Unless rcu_sched kthread gets sufficient CPU time, OOM is now expected behavior.
> [ 56.516681] rcu: RCU grace-period kthread stack dump:
> [ 56.521803] task:rcu_sched state:I stack:0 pid:13 tgid:13 ppid:2 flags:0x00000000
> [ 56.531267] __schedule from schedule+0x20/0xe8
> [ 56.535883] schedule from schedule_timeout+0xa0/0x158
> [ 56.541111] schedule_timeout from rcu_gp_fqs_loop+0x104/0x594
> [ 56.547048] rcu_gp_fqs_loop from rcu_gp_kthread+0x14c/0x1c0
> [ 56.552801] rcu_gp_kthread from kthread+0xe0/0xfc
> [ 56.557674] kthread from ret_from_fork+0x14/0x28
> [ 56.562457] Exception stack(0xf084dfb0 to 0xf084dff8)
> [ 56.567584] dfa0: 00000000 00000000 00000000 00000000
> [ 56.575886] dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> [ 56.584191] dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
> [ 56.590907] rcu: Stack dump where RCU GP kthread last ran:
> [ 56.596474] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.7.0-rc1-00006-gc8d312e03903 #1
> [ 56.604515] Hardware name: BCM2835
> [ 56.607965] PC is at default_idle_call+0x1c/0xb0
> [ 56.612654] LR is at ct_kernel_enter.constprop.0+0x48/0x11c
> [ 56.618311] pc : [<c1197054>] lr : [<c1195c98>] psr: 60010013
> [ 56.624672] sp : c1b01f70 ip : c1d5af7c fp : 00000000
> [ 56.629974] r10: c19cda60 r9 : 00000000 r8 : 00000000
> [ 56.635277] r7 : c1b04d50 r6 : c1b04d18 r5 : c1d5b684 r4 : c1b09740
> [ 56.641902] r3 : 00000000 r2 : 00000000 r1 : 00000001 r0 : 002a3114
> [ 56.648528] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
> [ 56.655774] Control: 10c5383d Table: 0237406a DAC: 00000051
> [ 56.661605] default_idle_call from do_idle+0x208/0x290
> [ 56.666920] do_idle from cpu_startup_entry+0x28/0x2c
> [ 56.672059] cpu_startup_entry from rest_init+0xac/0xb0
> [ 56.677371] rest_init from arch_post_acpi_subsys_init+0x0/0x8
> Login ti
>
> A full log for that run can be seen at:
>
> https://validation.linaro.org/scheduler/job/4017095
>
> Boots to initramfs with the same kernel image seem fine. Other systems,
> including other 32 bit arm ones, don't seem to be having similar issues
> with this userspace. I've not investigated beyond running the bisect,
> the log for which is below:
>
> git bisect start
> # good: [64e6d94bfb47ed0732ad06aedf8ec6af5dd2ab84] Merge branch 'for-linux-next-fixes' of git://anongit.freedesktop.org/drm/drm-misc
> git bisect good 64e6d94bfb47ed0732ad06aedf8ec6af5dd2ab84
> # bad: [5a82d69d48c82e89aef44483d2a129f869f3506a] Add linux-next specific files for 20231120
> git bisect bad 5a82d69d48c82e89aef44483d2a129f869f3506a
> # good: [ce252a92a867da8a6622463bff637e5f7b904a46] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless-next.git
> git bisect good ce252a92a867da8a6622463bff637e5f7b904a46
> # good: [c22e026efad504e3b056d4436920d173a09c580e] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git
> git bisect good c22e026efad504e3b056d4436920d173a09c580e
> # good: [b7fc58ffb105470cb339163cc2b04e3f59387a45] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/fpga/linux-fpga.git
> git bisect good b7fc58ffb105470cb339163cc2b04e3f59387a45
> # good: [26f89f0614f03e4016578a992fc2e86b048a5cb4] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl.git
> git bisect good 26f89f0614f03e4016578a992fc2e86b048a5cb4
> # good: [602bf18307981f3bfd9ebf19921791a4256d3fd1] Merge branch 'for-6.7' into for-next
> git bisect good 602bf18307981f3bfd9ebf19921791a4256d3fd1
> # good: [9f16a68069822b1df6bfb8a9ef7258a1e32b25e7] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching
> git bisect good 9f16a68069822b1df6bfb8a9ef7258a1e32b25e7
> # good: [3ff57db6f6569ebc2cc333437e7e949749e59424] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/krisman/unicode.git
> git bisect good 3ff57db6f6569ebc2cc333437e7e949749e59424
> # bad: [dd374e220ba492f95344a638b1efe5b2744fdd73] slub: Update frozen slabs documentations in the source
> git bisect bad dd374e220ba492f95344a638b1efe5b2744fdd73
> # good: [a3058965bb35490454953aa2c87ea51004839f2f] slub: Prepare __slab_free() for unfrozen partial slab out of node partial list
> git bisect good a3058965bb35490454953aa2c87ea51004839f2f
> # bad: [c8d312e039030edab25836a326bcaeb2a3d4db14] slub: Delay freezing of partial slabs
> git bisect bad c8d312e039030edab25836a326bcaeb2a3d4db14
> # good: [00b15a19ee543f0117cb217fcbab8b7b3fd50677] slub: Introduce freeze_slab()
> git bisect good 00b15a19ee543f0117cb217fcbab8b7b3fd50677
> # first bad commit: [c8d312e039030edab25836a326bcaeb2a3d4db14] slub: Delay freezing of partial slabs
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