Date:   Sun, 11 Jul 2021 21:14:23 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>
Subject: Re: Linux 5.14-rc1

On Sun, Jul 11, 2021 at 06:56:21PM -0700, Guenter Roeck wrote:
> On Sun, Jul 11, 2021 at 03:49:31PM -0700, Linus Torvalds wrote:
> > You all know the drill by now. It's been the usual two weeks of merge
> > window, and not it's closed, and 5.14-rc1 is out there.
> > 
> [ ... ] 
> > Please do test, and we can get the whole calming-down period rolling
> > and hopefully get a timely final 5.14 release.
> > 
> 
[ ... ]
> 
> WARNING: CPU: 0 PID: 24 at block/genhd.c:484 __device_add_disk+0x248/0x286
> 
> This is seen with riscv64 images when booting from usb or scsi drives.
> I don't recall seeing this warning before, but I may have missed it
> in the flurry of other warnings. It may have been introduced with commit
> 7c3f828b522b0 ("block: refactor device number setup in __device_add_disk")
> but I did not try to bisect it yet.
> 
My guess was correct. Bisect points to the above commit. Bisect log as well
as complete backtrace and example qemu command attached.

Copying Christoph and Jens.

Guenter

---
# bad: [3dbdb38e286903ec220aaf1fb29a8d94297da246] Merge branch 'for-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
# good: [007b350a58754a93ca9fe50c498cc27780171153] Merge tag 'dlm-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm
git bisect start '3dbdb38e2869' '007b350a5875'
# good: [b6df00789e2831fff7a2c65aa7164b2a4dcbe599] Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
git bisect good b6df00789e2831fff7a2c65aa7164b2a4dcbe599
# good: [990ec3014deedfed49e610cdc31dc6930ca63d8d] drm/amdgpu: add psp runtime db structures
git bisect good 990ec3014deedfed49e610cdc31dc6930ca63d8d
# bad: [c288d9cd710433e5991d58a0764c4d08a933b871] Merge tag 'for-5.14/io_uring-2021-06-30' of git://git.kernel.dk/linux-block
git bisect bad c288d9cd710433e5991d58a0764c4d08a933b871
# bad: [df668a5fe461bb9d7e899c538acc7197746038f4] Merge tag 'for-5.14/block-2021-06-29' of git://git.kernel.dk/linux-block
git bisect bad df668a5fe461bb9d7e899c538acc7197746038f4
# good: [4b5e35ce075817bc36d7c581b22853be984e5b41] Merge tag 'edac_updates_for_v5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/ras/ras
git bisect good 4b5e35ce075817bc36d7c581b22853be984e5b41
# bad: [e42cfb1da0bf33c313318da201730324c423351d] block: Remove unnecessary elevator operation checks
git bisect bad e42cfb1da0bf33c313318da201730324c423351d
# bad: [c97d93c31e5734a16bfe663085ec91b8c9fb20f9] block: factor out a part_devt helper
git bisect bad c97d93c31e5734a16bfe663085ec91b8c9fb20f9
# bad: [7681750bd35fe92dd915f4df177d45265e78a933] zram: convert to blk_alloc_disk/blk_cleanup_disk
git bisect bad 7681750bd35fe92dd915f4df177d45265e78a933
# good: [56b68085e536eff2676108f2f8356889a7dbbf55] blk-mq: Some tag allocation code refactoring
git bisect good 56b68085e536eff2676108f2f8356889a7dbbf55
# bad: [958229a7c55f219b1cff99f939dabbc1b6ba7161] block: add a flag to make put_disk on partially initalized disks safer
git bisect bad 958229a7c55f219b1cff99f939dabbc1b6ba7161
# bad: [7c3f828b522b07adb341b08fde1660685c5ba3eb] block: refactor device number setup in __device_add_disk
git bisect bad 7c3f828b522b07adb341b08fde1660685c5ba3eb
# good: [d97e594c51660bea510a387731637b894651e4b5] blk-mq: Use request queue-wide tags for tagset-wide sbitmap
git bisect good d97e594c51660bea510a387731637b894651e4b5
# first bad commit: [7c3f828b522b07adb341b08fde1660685c5ba3eb] block: refactor device number setup in __device_add_disk

---
[   11.940230] Waiting for root device /dev/sda...
[   12.066026] usb 1-1: new full-speed USB device number 2 using ohci-pci
[   12.306673] usb-storage 1-1:1.0: USB Mass Storage device detected
[   12.310957] scsi host0: usb-storage 1-1:1.0
[   13.354722] scsi 0:0:0:0: Direct-Access     QEMU     QEMU HARDDISK    2.5+ PQ: 0 ANSI: 5
[   13.370433] sd 0:0:0:0: Power-on or device reset occurred
[   13.390621] sd 0:0:0:0: [sda] 32768 512-byte logical blocks: (16.8 MB/16.0 MiB)
[   13.396348] sd 0:0:0:0: [sda] Write Protect is off
[   13.402622] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[   13.403994] ------------[ cut here ]------------
[   13.404165] WARNING: CPU: 0 PID: 7 at block/genhd.c:484 __device_add_disk+0x248/0x286
[   13.404393] Modules linked in:
[   13.404601] CPU: 0 PID: 7 Comm: kworker/u2:0 Not tainted 5.14.0-rc1 #1
[   13.404830] Hardware name: riscv-virtio,qemu (DT)
[   13.405081] Workqueue: events_unbound async_run_entry_fn
[   13.405309] epc : __device_add_disk+0x248/0x286
[   13.405496]  ra : __device_add_disk+0x1b2/0x286
[   13.405657] epc : ffffffff8042a4cc ra : ffffffff8042a436 sp : ffffffd00024bb80
[   13.405863]  gp : ffffffff819d15a8 tp : ffffffe0027a8040 t0 : ffffffe01f6f48f8
[   13.406087]  t1 : 000000006faf79ac t2 : 00000000000001a5 s0 : ffffffd00024bbc0
[   13.406293]  s1 : ffffffe004450e00 a0 : 0000000000006000 a1 : ffffffe0027a88b0
[   13.406499]  a2 : ffffffff819e2890 a3 : 0000000000000000 a4 : 0000000000000008
[   13.406703]  a5 : 0000000000000000 a6 : 0000000000001fff a7 : 0000000000000000
[   13.406908]  s2 : ffffffe004450e00 s3 : 0000000000000001 s4 : 0000000000000000
[   13.407135]  s5 : ffffffe00438c268 s6 : 0000000000000000 s7 : 0000000000000000
[   13.407344]  s8 : ffffffff819d41b8 s9 : ffffffff819d4298 s10: ffffffe00261a858
[   13.407550]  s11: ffffffe00261a8d0 t3 : 0000000045db8cae t4 : 000000000000000c
[   13.407752]  t5 : fffffffff04a2835 t6 : 0000000000001fff
[   13.407912] status: 0000000000000120 badaddr: 0000000000000000 cause: 0000000000000003
[   13.408179] [<ffffffff8042a4cc>] __device_add_disk+0x248/0x286
[   13.408394] [<ffffffff8042a518>] device_add_disk+0xe/0x16
[   13.408555] [<ffffffff806e3886>] sd_probe+0x2b8/0x366
[   13.408711] [<ffffffff8067bce4>] really_probe.part.0+0x188/0x222
[   13.408886] [<ffffffff8067be16>] __driver_probe_device+0x98/0xbe
[   13.409079] [<ffffffff8067be68>] driver_probe_device+0x2c/0xb0
[   13.409247] [<ffffffff8067c330>] __device_attach_driver+0x62/0x9a
[   13.409419] [<ffffffff80679c7e>] bus_for_each_drv+0x5c/0xa2
[   13.409580] [<ffffffff8067b458>] __device_attach_async_helper+0x88/0x92
[   13.409766] [<ffffffff80032e12>] async_run_entry_fn+0x22/0xc4
[   13.409930] [<ffffffff80027e28>] process_one_work+0x1f4/0x53a
[   13.410114] [<ffffffff800281ec>] worker_thread+0x7e/0x324
[   13.410272] [<ffffffff8002fa1e>] kthread+0x100/0x116
[   13.410419] [<ffffffff80003648>] ret_from_exception+0x0/0x10
[   13.410614] irq event stamp: 59724
[   13.410733] hardirqs last  enabled at (59723): [<ffffffff80a1471c>] _raw_spin_unlock_irqrestore+0x54/0x62
[   13.411019] hardirqs last disabled at (59724): [<ffffffff80003592>] _save_context+0x7c/0xe0
[   13.411249] softirqs last  enabled at (34082): [<ffffffff80a1510a>] __do_softirq+0x39a/0x520
[   13.411496] softirqs last disabled at (34073): [<ffffffff80014354>] irq_exit+0xd2/0xde
[   13.411733] ---[ end trace 644c7abe39308f0f ]---
[   13.480431] sd 0:0:0:0: [sda] Attached SCSI disk
[   13.511335] EXT4-fs (sda): mounting ext2 file system using the ext4 subsystem
[   13.536810] EXT4-fs (sda): mounted filesystem without journal. Opts: (null). Quota mode: disabled.
[   13.537632] VFS: Mounted root (ext2 filesystem) readonly on device 8:0.

---

Sample qemu command:

qemu-system-riscv64 -M virt -m 512M \
     -no-reboot -bios default -kernel arch/riscv/boot/Image \
     -snapshot -device virtio-net-device,netdev=net0 -netdev user,id=net0 \
     -usb -device pci-ohci,id=ohci -device usb-storage,bus=ohci.0,drive=d0 \
     -drive file=/var/cache/buildbot/riscv64/rootfs.ext2,if=none,id=d0,format=raw \
     -append "root=/dev/sda rootwait console=ttyS0,115200 earlycon=uart8250,mmio,0x10000000,115200" \
     -nographic -monitor none

The problem is seen with various USB boot variants (ohcu, ehci, xhci, uas-ehci,
uas-xhci) and all SCSI controllers supported by qemu.

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