Atomic test-and-set instruction does not work on qemu-user

Bug #1908626 reported by taos
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
QEMU
Undecided
Unassigned

Bug Description

I try to compile and run PostgreSQL/Greenplum database inside docker container/qemu-aarch64-static:
```
 host: CentOS7 x86_64
 container: centos:centos7.9.2009 --platform linux/arm64/v8
 qemu-user-static: https://github.com/multiarch/qemu-user-static/releases/
```

However, GP/PG's spinlock always gets stuck and reports PANIC errors. It seems its spinlock
has something wrong.
```
https://github.com/greenplum-db/gpdb/blob/master/src/include/storage/s_lock.h
https://github.com/greenplum-db/gpdb/blob/master/src/backend/storage/lmgr/s_lock.c
```

So I extract its spinlock implementation into one test C source file (see attachment file),
and get reprodcued:

```
$ gcc spinlock_qemu.c
$ ./a.out
C -- slock inited, lock value is: 0
parent 139642, child 139645
P -- slock lock before, lock value is: 0
P -- slock locked, lock value is: 1
P -- slock unlock after, lock value is: 0
C -- slock lock before, lock value is: 1
P -- slock lock before, lock value is: 1
C -- slock locked, lock value is: 1
C -- slock unlock after, lock value is: 0
C -- slock lock before, lock value is: 1
P -- slock locked, lock value is: 1
P -- slock unlock after, lock value is: 0
P -- slock lock before, lock value is: 1
C -- slock locked, lock value is: 1
C -- slock unlock after, lock value is: 0
P -- slock locked, lock value is: 1
C -- slock lock before, lock value is: 1
P -- slock unlock after, lock value is: 0
C -- slock locked, lock value is: 1
P -- slock lock before, lock value is: 1
C -- slock unlock after, lock value is: 0
P -- slock locked, lock value is: 1
C -- slock lock before, lock value is: 1
P -- slock unlock after, lock value is: 0
C -- slock locked, lock value is: 1
P -- slock lock before, lock value is: 1
C -- slock unlock after, lock value is: 0
P -- slock locked, lock value is: 1
C -- slock lock before, lock value is: 1
P -- slock unlock after, lock value is: 0
P -- slock lock before, lock value is: 1
spin timeout, lock value is 1 (pid 139642)
spin timeout, lock value is 1 (pid 139645)
spin timeout, lock value is 1 (pid 139645)
spin timeout, lock value is 1 (pid 139642)
spin timeout, lock value is 1 (pid 139645)
spin timeout, lock value is 1 (pid 139642)
...
...
...
```

NOTE: this code always works on PHYSICAL ARM64 server.

Revision history for this message
taos (ggbq) wrote :
tags: added: linux-user
Revision history for this message
taos (ggbq) wrote :

Interestingly, the spinlock test works after I change tas() implementation
FROM
  __sync_lock_test_and_set(lock, 1);
TO
  __sync_val_compare_and_swap(lock, 0, 1);

## gcc (GCC) 8.3.1 20190311 (Red Hat 8.3.1-3)

====
__sync_lock_test_and_set(lock, 1) disassembly:

```
objdump -S a.out

000000000040073c <tas>:
  40073c: d10043ff sub sp, sp, #0x10
  400740: f90007e0 str x0, [sp, #8]
  400744: f94007e0 ldr x0, [sp, #8]
  400748: 52800021 mov w1, #0x1 // #1
  40074c: 885f7c02 ldxr w2, [x0]
  400750: 88037c01 stxr w3, w1, [x0]
  400754: 35ffffc3 cbnz w3, 40074c <tas+0x10>
  400758: d5033bbf dmb ish
  40075c: 2a0203e0 mov w0, w2
  400760: 910043ff add sp, sp, #0x10
  400764: d65f03c0 ret
```

====
__sync_val_compare_and_swap(lock, 0, 1); disassembly:

```
objdump -S a.out

000000000040073c <tas>:
  40073c: d10043ff sub sp, sp, #0x10
  400740: f90007e0 str x0, [sp, #8]
  400744: f94007e0 ldr x0, [sp, #8]
  400748: 52800021 mov w1, #0x1 // #1
  40074c: 885f7c02 ldxr w2, [x0]
  400750: 35000062 cbnz w2, 40075c <tas+0x20>
  400754: 8803fc01 stlxr w3, w1, [x0]
  400758: 35ffffa3 cbnz w3, 40074c <tas+0x10>
  40075c: 7100005f cmp w2, #0x0
  400760: d5033bbf dmb ish
  400764: 2a0203e0 mov w0, w2
  400768: 910043ff add sp, sp, #0x10
  40076c: d65f03c0 ret
```

Revision history for this message
Thomas Huth (th-huth) wrote :

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" or "Confirmed" within the next 60 days (other-
wise it will get closed as "Expired"). We will then eventually migrate
the ticket automatically to the new system (but you won't be the reporter
of the bug in the new system and thus you won't get notified on changes
anymore).

Thank you and sorry for the inconvenience.

Changed in qemu:
status: New → Incomplete
Revision history for this message
Launchpad Janitor (janitor) wrote :

[Expired for QEMU because there has been no activity for 60 days.]

Changed in qemu:
status: Incomplete → Expired
taos (ggbq)
Changed in qemu:
status: Expired → New
Revision history for this message
Thomas Huth (th-huth) wrote : Moved bug report

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/509

Changed in qemu:
status: New → Expired
Revision history for this message
Thomas Huth (th-huth) wrote :

Hi taos! Could you please check whether this has been fixed already in QEMU v6.1.0-rc1 ?

Revision history for this message
taos (ggbq) wrote :

Thanks. Tested, the problem is gone.

To post a comment you must log in.
This report contains Public information  Edit
Everyone can see this information.

Other bug subscribers

Bug attachments

Remote bug watches

Bug watches keep track of this bug in other bug trackers.