Re: bpf VM_FLUSH_RESET_PERMS breaks sparc64 boot

["Edgecombe, Rick P" <rick.p.edgecombe@intel.com>]

On Mon, 2019-05-13 at 17:01 +0300, Meelis Roos wrote:
> I tested yesterdays 5.2 devel git and it failed to boot on my Sun Fire V445
> (4x UltraSparc III). Init is started and it hangs there:
> 
> [   38.414436] Run /sbin/init as init process
> [   38.530711] random: fast init done
> [   39.580678] systemd[1]: Inserted module 'autofs4'
> [   39.721577] systemd[1]: systemd 241 running in system mode. (+PAM +AUDIT
> +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS
> +ACL +XZ +LZ4 -SECCOMP +BLKID +ELFUTILS +KMOD -IDN2 +IDN -PCRE2 default-
> hierarchy=hybrid)
> [   40.028068] systemd[1]: Detected architecture sparc64.
> 
> Welcome to Debian GNU/Linux 10 (buster)!
> 
> [   40.168713] systemd[1]: Set hostname to <v445>.
> [   61.318034] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
> [   61.403039] rcu:     1-...!: (0 ticks this GP)
> idle=602/1/0x4000000000000000 softirq=85/85 fqs=1
> [   61.526780] rcu:     (detected by 3, t=5252 jiffies, g=-967, q=228)
> [   61.613037]   CPU[  1]: TSTATE[0000000080001602] TPC[000000000043f2b8]
> TNPC[000000000043f2bc] TASK[systemd-fstab-g:90]
> [   61.766828]              TPC[smp_synchronize_tick_client+0x18/0x180]
> O7[__do_munmap+0x204/0x3e0] I7[xcall_sync_tick+0x1c/0x2c]
> RPC[page_evictable+0x4/0x60]
> [   61.966807] rcu: rcu_sched kthread starved for 5250 jiffies! g-967 f0x0
> RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=2
> [   62.113058] rcu: RCU grace-period kthread stack dump:
> [   62.185558] rcu_sched       I    0    10      2 0x06000000
> [   62.264312] Call Trace:
> [   62.299316]  [000000000092a1fc] schedule+0x1c/0x80
> [   62.368071]  [000000000092d3fc] schedule_timeout+0x13c/0x280
> [   62.449328]  [00000000004b6c64] rcu_gp_kthread+0x4c4/0xa40
> [   62.528077]  [000000000047e95c] kthread+0xfc/0x120
> [   62.596833]  [00000000004060a4] ret_from_fork+0x1c/0x2c
> [   62.671831]  [0000000000000000]           (null)
> 
> 5.1.0 worked fine. I bisected it to the following commit:
> 
> d53d2f78ceadba081fc7785570798c3c8d50a718 is the first bad commit
> commit d53d2f78ceadba081fc7785570798c3c8d50a718
> Author: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Date:   Thu Apr 25 17:11:38 2019 -0700
> 
>      bpf: Use vmalloc special flag
>      
>      Use new flag VM_FLUSH_RESET_PERMS for handling freeing of special
>      permissioned memory in vmalloc and remove places where memory was set RW
>      before freeing which is no longer needed. Don't track if the memory is RO
>      anymore because it is now tracked in vmalloc.
>      
>      Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
>      Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>      Cc: <akpm@linux-foundation.org>
>      Cc: <ard.biesheuvel@linaro.org>
>      Cc: <deneen.t.dock@intel.com>
>      Cc: <kernel-hardening@lists.openwall.com>
>      Cc: <kristen@linux.intel.com>
>      Cc: <linux_dti@icloud.com>
>      Cc: <will.deacon@arm.com>
>      Cc: Alexei Starovoitov <ast@kernel.org>
>      Cc: Andy Lutomirski <luto@kernel.org>
>      Cc: Borislav Petkov <bp@alien8.de>
>      Cc: Daniel Borkmann <daniel@iogearbox.net>
>      Cc: Dave Hansen <dave.hansen@linux.intel.com>
>      Cc: H. Peter Anvin <hpa@zytor.com>
>      Cc: Linus Torvalds <torvalds@linux-foundation.org>
>      Cc: Nadav Amit <nadav.amit@gmail.com>
>      Cc: Rik van Riel <riel@surriel.com>
>      Cc: Thomas Gleixner <tglx@linutronix.de>
>      Link: https://lkml.kernel.org/r/20190426001143.4983-19-namit@vmware.com
>      Signed-off-by: Ingo Molnar <mingo@kernel.org>
> 
> :040000 040000 58066de53107eab0705398b5d0c407424c138a86
> 7a1345d43c4cacee60b9135899b775ecdb54ea7e M      include
> :040000 040000 d02692cf57a359056b34e636d0f102d37de5b264
> 81c4c2c6408b68eb555673bd3f0bc3071db1f7ed M      kernel
> 
Thanks, I'll see if I can reproduce.

Rick