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Re: [Qemu-devel] [PATCH] linux-user/main.c: Remove redundant end_exclusi


From: Peter Maydell
Subject: Re: [Qemu-devel] [PATCH] linux-user/main.c: Remove redundant end_exclusive()
Date: Fri, 23 Jan 2015 10:20:51 +0000

On 23 January 2015 at 10:17, Chen Gang S <address@hidden> wrote:
> start/end_exclusive() need be pairs, except the start_exclusive() in
> stop_all_tasks() which is only used by force_sig(), which will be abort.
> So at present, start_exclusive() in stop_all_task() need not be paired.
>
> So need remove end_exclusive() after queue_signal(). If could really
> return from queue_signal(), which meant stop_all_task() is not called (
> at least, not called in time), the next end_exclusive() would be issue.
>
> Also use TARGET_SIGSEGV instead of SIGSEGV, since queue_signal() is for
> TARGET_*, at present, queue_signal() is a normal function which may call
> force_sig(), or return (may kill pid or queue signal, then return).

It would be helpful to mention the affected target architecture
(and/or function name) in the commit message, because main.c covers
a lot of ground.

> Signed-off-by: Chen Gang <address@hidden>
> ---
>  linux-user/main.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 8c70be4..a410a17 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -517,14 +517,12 @@ segv:
>      end_exclusive();
>      /* We get the PC of the entry address - which is as good as anything,
>         on a real kernel what you get depends on which mode it uses. */
> -    info.si_signo = SIGSEGV;
> +    info.si_signo = TARGET_SIGSEGV;

I think this is a correct bug fix, but it's not really related
to the main point of the patch (fixing end_exclusive()) and
there are actually a lot of instances of it in this file and
possibly others. Could you fix it (and those others) in a separate
patch, please?

>      info.si_errno = 0;
>      /* XXX: check env->error_code */
>      info.si_code = TARGET_SEGV_MAPERR;
>      info._sifields._sigfault._addr = env->exception.vaddress;
>      queue_signal(env, info.si_signo, &info);
> -
> -    end_exclusive();
>  }

This change is correct.

thanks
-- PMM



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