Re: [PATCH 13/19] accel/tcg: Fixed tsan warnings.

[Paolo Bonzini]

On 22/05/20 18:07, Robert Foley wrote:
> For example:
> WARNING: ThreadSanitizer: data race (pid=35425)
>   Write of size 4 at 0x7bbc000000ac by main thread (mutexes: write M875):
>     #0 cpu_reset_interrupt hw/core/cpu.c:107:28 (qemu-system-aarch64+0x843790)
>     #1 arm_cpu_set_irq target/arm/cpu.c (qemu-system-aarch64+0x616265)
>     #2 qemu_set_irq hw/core/irq.c:44:5 (qemu-system-aarch64+0x8462ca)
>   Previous atomic read of size 4 at 0x7bbc000000ac by thread T6:
>     #0 __tsan_atomic32_load <null> (qemu-system-aarch64+0x394c1c)
>     #1 cpu_handle_interrupt accel/tcg/cpu-exec.c:534:9 
> (qemu-system-aarch64+0x4b7e79)
>     #2 cpu_exec accel/tcg/cpu-exec.c:720:17 (qemu-system-aarch64+0x4b7e79)
> or
> WARNING: ThreadSanitizer: data race (pid=25425)
>   Read of size 8 at 0x7f8ad8e138d0 by thread T10:
>     #0 tb_lookup_cmp accel/tcg/cpu-exec.c:307:13 
> (qemu-system-aarch64+0x4ac4d2)
>     #1 qht_do_lookup util/qht.c:502:34 (qemu-system-aarch64+0xd05264)
>   Previous write of size 8 at 0x7f8ad8e138d0 by thread T15 (mutexes: write 
> M728311726235541804):
>     #0 tb_link_page accel/tcg/translate-all.c:1625:26 
> (qemu-system-aarch64+0x4b0bf2)
>     #1 tb_gen_code accel/tcg/translate-all.c:1865:19 
> (qemu-system-aarch64+0x4b0bf2)
>     #2 tb_find accel/tcg/cpu-exec.c:407:14 (qemu-system-aarch64+0x4ad77c)
> 
> Cc: Richard Henderson <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Signed-off-by: Robert Foley <address@hidden>
> ---
>  accel/tcg/tcg-all.c       | 4 ++--
>  accel/tcg/tcg-runtime.c   | 7 ++++++-
>  accel/tcg/translate-all.c | 6 +++++-
>  hw/core/cpu.c             | 2 +-
>  4 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
> index 3b4fda5640..f94ea4c4b3 100644
> --- a/accel/tcg/tcg-all.c
> +++ b/accel/tcg/tcg-all.c
> @@ -54,8 +54,8 @@ static void tcg_handle_interrupt(CPUState *cpu, int mask)
>      int old_mask;
>      g_assert(qemu_mutex_iothread_locked());
>  
> -    old_mask = cpu->interrupt_request;
> -    cpu->interrupt_request |= mask;
> +    old_mask = atomic_read(&cpu->interrupt_request);
> +    atomic_or(&cpu->interrupt_request, mask);

You can use atomic_fetch_or here.

Paolo