ACK: [B][SRU][PATCH 0/5] Fix for cfs_bandwidth01 test in LTP/sched
Tim Gardner
tim.gardner at canonical.com
Tue Jun 22 11:29:49 UTC 2021
Acked-by: Tim Gardner <tim.gardner at canonical.com>
Kind of a tricky backport.
On 6/22/21 1:49 AM, po-hsu.lin at canonical.com wrote:
> From: Po-Hsu Lin <po-hsu.lin at canonical.com>
>
> [Impact]
> Test case cfs_bandwidth01 in LTP sched test suite is a reproducer
> of a CFS unthrottle_cfs_rq() issue (fe61468b2cbc2b sched/fair: Fix
> enqueue_task_fair warning).
>
> This test triggers a warning on our 4.15 kernel:
> LTP: starting cfs_bandwidth01 (cfs_bandwidth01 -i 5)
> ------------[ cut here ]------------
> rq->tmp_alone_branch != &rq->leaf_cfs_rq_list
> WARNING: CPU: 0 PID: 0 at /build/linux-fYK9kF/linux-4.15.0/kernel/sched/fair.c:393 unthrottle_cfs_rq+0x16f/0x200
> Modules linked in: input_leds joydev serio_raw mac_hid qemu_fw_cfg kvm_intel kvm irqbypass sch_fq_codel binfmt_misc ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi nfsd auth_rpcgss nfs_acl lockd grace sunrpc ip_tables x_tables autofs4 btrfs zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear cirrus ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm psmouse virtio_blk pata_acpi floppy virtio_net i2c_piix4
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-144-generic #148-Ubuntu
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> RIP: 0010:unthrottle_cfs_rq+0x16f/0x200
> RSP: 0018:ffff989ebfc03e80 EFLAGS: 00010082
> RAX: 0000000000000000 RBX: ffff989eb4c6ac00 RCX: 0000000000000000
> RDX: 0000000000000005 RSI: ffffffffacb63c4d RDI: 0000000000000046
> RBP: ffff989ebfc03ea8 R08: 000000af39e61b33 R09: ffffffffacb63c20
> R10: 0000000000000000 R11: 0000000000000001 R12: ffff989eb57fe400
> R13: ffff989ebfc21900 R14: 0000000000000001 R15: 0000000000000001
> FS: 0000000000000000(0000) GS:ffff989ebfc00000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055593258d618 CR3: 000000007a044000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <IRQ>
> distribute_cfs_runtime+0xc3/0x110
> sched_cfs_period_timer+0xff/0x220
> ? sched_cfs_slack_timer+0xd0/0xd0
> __hrtimer_run_queues+0xdf/0x230
> hrtimer_interrupt+0xa0/0x1d0
> smp_apic_timer_interrupt+0x6f/0x140
> apic_timer_interrupt+0x90/0xa0
> </IRQ>
> RIP: 0010:native_safe_halt+0x12/0x20
> RSP: 0018:ffffffffac603e28 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff11
> RAX: ffffffffabbc9280 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffffffac603e28 R08: 000000af39850067 R09: ffff989e73749d00
> R10: 0000000000000000 R11: 7fffffffffffffff R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> ? __sched_text_end+0x1/0x1
> default_idle+0x20/0x100
> arch_cpu_idle+0x15/0x20
> default_idle_call+0x23/0x30
> do_idle+0x172/0x1f0
> cpu_startup_entry+0x73/0x80
> rest_init+0xae/0xb0
> start_kernel+0x4dc/0x500
> x86_64_start_reservations+0x24/0x26
> x86_64_start_kernel+0x74/0x77
> secondary_startup_64+0xa5/0xb0
> Code: 50 09 00 00 49 39 85 60 09 00 00 74 68 80 3d 3a 6e 54 01 00 75 5f 31 db 48 c7 c7 c0 3d 2d ac c6 05 28 6e 54 01 01 e8 11 36 fc ff <0f> 0b 48 85 db 74 43 49 8b 85 78 09 00 00 49 39 85 70 09 00 00
> ---[ end trace b6b9a70bc2945c0c ]---
>
> [Fix]
> Base on the test case description, we will need these fixes:
> * fe61468b2cbc2b sched/fair: Fix enqueue_task_fair warning
> * b34cb07dde7c23 sched/fair: Fix enqueue_task_fair() warning some more
> * 39f23ce07b9355 sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list
> * 6d4d22468dae3d sched/fair: Reorder enqueue/dequeue_task_fair path
> * 5ab297bab98431 sched/fair: Fix reordering of enqueue/dequeue_task_fair()
>
> Backport needed for Bionic since we're missing some new variables /
> coding style changes introduced in the following commits (and their
> corresponding fixes):
> * 97fb7a0a8944bd sched: Clean up and harmonize the coding style of the scheduler code base
> * 9f68395333ad7f sched/pelt: Add a new runnable average signal
> * 6212437f0f6043 sched/fair: Fix runnable_avg for throttled cfs
> * 43e9f7f231e40e sched/fair: Start tracking SCHED_IDLE tasks count in cfs_rq
>
> I have also searched in the upstream tree to see if there is any other
> commit claim to be a fix of these but didn't see any.
>
> [Test]
> Test kernel can be found here:
> https://people.canonical.com/~phlin/kernel/lp-1931325-cfs_bandwidth01/
>
> With these patches applied, the test can pass without triggering this
> warning.
>
> <<<test_start>>>
> tag=cfs_bandwidth01 stime=1624260713
> cmdline="cfs_bandwidth01 -i 5"
> contacts=""
> analysis=exit
> <<<test_output>>>
> incrementing stop
> tst_test.c:1313: TINFO: Timeout per run is 0h 05m 00s
> tst_buffers.c:55: TINFO: Test is using guarded buffers
> cfs_bandwidth01.c:49: TINFO: Set 'worker1/cpu.max' = '3000 10000'
> cfs_bandwidth01.c:49: TINFO: Set 'worker2/cpu.max' = '2000 10000'
> cfs_bandwidth01.c:49: TINFO: Set 'worker3/cpu.max' = '3000 10000'
> cfs_bandwidth01.c:113: TPASS: Scheduled bandwidth constrained workers
> cfs_bandwidth01.c:49: TINFO: Set 'level2/cpu.max' = '5000 10000'
> cfs_bandwidth01.c:125: TPASS: Workers exited
> cfs_bandwidth01.c:113: TPASS: Scheduled bandwidth constrained workers
> cfs_bandwidth01.c:49: TINFO: Set 'level2/cpu.max' = '5000 10000'
> cfs_bandwidth01.c:125: TPASS: Workers exited
> cfs_bandwidth01.c:113: TPASS: Scheduled bandwidth constrained workers
> cfs_bandwidth01.c:49: TINFO: Set 'level2/cpu.max' = '5000 10000'
> cfs_bandwidth01.c:125: TPASS: Workers exited
> cfs_bandwidth01.c:113: TPASS: Scheduled bandwidth constrained workers
> cfs_bandwidth01.c:49: TINFO: Set 'level2/cpu.max' = '5000 10000'
> cfs_bandwidth01.c:125: TPASS: Workers exited
> cfs_bandwidth01.c:113: TPASS: Scheduled bandwidth constrained workers
> cfs_bandwidth01.c:49: TINFO: Set 'level2/cpu.max' = '5000 10000'
> cfs_bandwidth01.c:125: TPASS: Workers exited
>
> Summary:
> passed 10
> failed 0
> broken 0
> skipped 0
> warnings 0
>
> I have also run the whole sched test suite in LTP to make sure there
> is no other issues caused by this patchset.
>
> [Where problems could occur]
> * CFS (Completely Fair Scheduler) is the process scheduling system in
> the kernel, if the patch is incorrect it might affect the sched
> functionality. Especially system with CONFIG_FAIR_GROUP_SCHED and
> CONFIG_CFS_BANDWIDTH enabled.
>
> [Other Info]
> Test case description:
> * Creates a multi-level CGroup hierarchy with the cpu controller
> * enabled. The leaf groups are populated with "busy" processes which
> * simulate intermittent cpu load. They spin for some time then sleep
> * then repeat.
> *
> * Both the trunk and leaf groups are set cpu bandwidth limits. The
> * busy processes will intermittently exceed these limits. Causing
> * them to be throttled. When they begin sleeping this will then cause
> * them to be unthrottle.
>
> Phil Auld (1):
> sched/fair: Fix enqueue_task_fair() warning some more
>
> Vincent Guittot (4):
> sched/fair: Fix enqueue_task_fair warning
> sched/fair: Reorder enqueue/dequeue_task_fair path
> sched/fair: Fix reordering of enqueue/dequeue_task_fair()
> sched/fair: Fix unthrottle_cfs_rq() for leaf_cfs_rq list
>
> kernel/sched/fair.c | 109 +++++++++++++++++++++++++++++++++++++---------------
> 1 file changed, 77 insertions(+), 32 deletions(-)
>
--
-----------
Tim Gardner
Canonical, Inc
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