Re: [Qemu-devel] [PATCH v2 04/11] translate: downgrade IRQ BQL asserts to tcg_debug_assert

[Peter Maydell]

On 2 March 2017 at 19:53, Alex Bennée <address@hidden> wrote:
> While on MTTCG hosts it is very important that updates to
> cpu->interrupt_request are protected by the BQL not all guests have
> been converted to the correct locking yet. As a result we are seeing
> breaking on non-MTTCG enabled guests in production builds.
>
> The locking in the guests needs to be fixed but while running single
> threaded they will continue to work. By moving the asserts to
> tcg_debug_asserts() they will still be useful during conversion
> work (much like the existing assert_memory_lock/assert_tb_lock
> asserts).
>
> Signed-off-by: Alex Bennée <address@hidden>
> ---
>  translate-all.c    | 2 +-
>  translate-common.c | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/translate-all.c b/translate-all.c
> index 9bac061c9b..7ee273410d 100644
> --- a/translate-all.c
> +++ b/translate-all.c
> @@ -1928,7 +1928,7 @@ void dump_opcount_info(FILE *f, fprintf_function 
> cpu_fprintf)
>
>  void cpu_interrupt(CPUState *cpu, int mask)
>  {
> -    g_assert(qemu_mutex_iothread_locked());
> +    tcg_debug_assert(qemu_mutex_iothread_locked());

If CONFIG_DEBUG_TCG isn't enabled then tcg_debug_assert()
turns into "if (!(X)) { __builtin_unreachable(); }", which
means that instead of asserting we now run straight
into compiler undefined behaviour, don't we?
If what we want is "don't actually check this condition in
the non-tcg-debug config" then we should do something
that means we don't actually check the condition...

thanks
-- PMM