Re: [PATCH v2 12/19] lib/stackdepot: use list_head for stack record links

[Anders Roxell]

On 2023-09-13 19:14, andrey.konovalov@xxxxxxxxx wrote:
> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> 
> Switch stack_record to use list_head for links in the hash table
> and in the freelist.
> 
> This will allow removing entries from the hash table buckets.
> 
> This is preparatory patch for implementing the eviction of stack records
> from the stack depot.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> 

Building on an arm64 kernel from linux-next tag next-20230915, and boot
that in QEMU. I see the following kernel panic.

[   67.398850][    T1] Unable to handle kernel read from unreadable memory at virtual address 0000000000000010
[   67.407996][    T1] Mem abort info:
[   67.411023][    T1]   ESR = 0x0000000096000004
[   67.414757][    T1]   EC = 0x25: DABT (current EL), IL = 32 bits
[   67.419945][    T1]   SET = 0, FnV = 0
[   67.423172][    T1]   EA = 0, S1PTW = 0
[   67.426669][    T1]   FSC = 0x04: level 0 translation fault
[   67.431357][    T1] Data abort info:
[   67.434593][    T1]   ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[   67.439801][    T1]   CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[   67.444948][    T1]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[   67.449910][    T1] [0000000000000010] user address but active_mm is swapper
[   67.456236][    T1] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[   67.462181][    T1] Modules linked in:
[   67.465435][    T1] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G                T  6.6.0-rc1-next-20230915 #2 e95cf19845fbc1e6a5f0694214d59e527e463469
[   67.477126][    T1] Hardware name: linux,dummy-virt (DT)
[   67.481994][    T1] pstate: 804000c5 (Nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   67.488454][    T1] pc : stack_depot_save_flags+0x2a8/0x780
[   67.493348][    T1] lr : stack_depot_save_flags+0x2a8/0x780
[   67.498339][    T1] sp : ffff80008000b870
[   67.501670][    T1] x29: ffff80008000b870 x28: 00000000650dddc5 x27: 0000000000000000
[   67.508658][    T1] x26: ffff80008470a000 x25: ffff80008000b9e8 x24: 0000000000000001
[   67.515564][    T1] x23: 000000000000000e x22: ffff80008000b988 x21: 0000000000000001
[   67.522430][    T1] x20: ffff00007b40d070 x19: 000000006ee80007 x18: ffff80008000d080
[   67.529365][    T1] x17: 0000000000000000 x16: 0000000000000000 x15: 2030303178302f30
[   67.536101][    T1] x14: 0000000000000000 x13: 205d315420202020 x12: 0000000000000000
[   67.542985][    T1] x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
[   67.549863][    T1] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
[   67.556764][    T1] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
[   67.563687][    T1] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
[   67.570500][    T1] Call trace:
[   67.573275][    T1]  stack_depot_save_flags+0x2a8/0x780
[   67.577794][    T1]  stack_depot_save+0x4c/0xc0
[   67.582062][    T1]  ref_tracker_alloc+0x354/0x480
[   67.586273][    T1]  sk_alloc+0x280/0x5f8
[   67.590064][    T1]  __netlink_create+0x84/0x200
[   67.594009][    T1]  __netlink_kernel_create+0x11c/0x500
[   67.598816][    T1]  rtnetlink_net_init+0xc4/0x180
[   67.603052][    T1]  ops_init+0x100/0x2c0
[   67.606827][    T1]  register_pernet_operations+0x228/0x480
[   67.611568][    T1]  register_pernet_subsys+0x5c/0xc0
[   67.616282][    T1]  rtnetlink_init+0x60/0xb00
[   67.620086][    T1]  netlink_proto_init+0x374/0x400
[   67.624465][    T1]  do_one_initcall+0x2c8/0x840
[   67.628518][    T1]  do_initcalls+0x21c/0x340
[   67.632527][    T1]  kernel_init_freeable+0x3b0/0x480
[   67.636905][    T1]  kernel_init+0x58/0x380
[   67.640768][    T1]  ret_from_fork+0x10/0x40
[   67.644606][    T1] Code: eb1b029f 540008c0 91004360 97caa437 (b9401360) 
[   67.650293][    T1] ---[ end trace 0000000000000000 ]---
[   67.654948][    T1] Kernel panic - not syncing: Oops: Fatal exception
[   67.660229][    T1] ---[ end Kernel panic - not syncing: Oops: Fatal exception ]---

The full log can be found [1] and the .config file [2]. I bisected down
to this commit, see the bisect log [3].

When reverted these two commits I managed to build and the kernel
booted.

47590ecf1166 ("lib/stackdepot: use list_head for stack record links")
8729f3c26fc2 ("lib/stackdepot: allow users to evict stack traces")


Cheers,
Anders
[1] http://ix.io/4GyE
[2] https://people.linaro.org/~anders.roxell/next-20230915.config
[3] http://ix.io/4GyG