Re: [Qemu-devel] qemu_futex_wait() lockups in ARM64: 2 possible issues

[Paolo Bonzini]

On 02/10/19 11:23, Jan Glauber wrote:
> I've tried to verify me theory with this patch and didn't run into the
> issue for ~500 iterations (usually I would trigger the issue ~20 iterations).

Awesome!  That would be a compiler bug though, as atomic_add and atomic_sub
are defined as sequentially consistent:

#define atomic_add(ptr, n) ((void) __atomic_fetch_add(ptr, n, __ATOMIC_SEQ_CST))
#define atomic_sub(ptr, n) ((void) __atomic_fetch_sub(ptr, n, __ATOMIC_SEQ_CST))

What compiler are you using and what distro?  Can you compile util/aio-posix.c
with "-fdump-rtl-all -fdump-tree-all", zip the boatload of debugging files and
send them my way?

Thanks,

Paolo