Re: [PATCH v4] elf: Avoid deadlock between pthread_create and ctors [BZ #28357]

[Andreas Schwab <schwab@linux-m68k.org>]

On Okt 01 2021, Szabolcs Nagy via Libc-alpha wrote:

> diff --git a/elf/dl-open.c b/elf/dl-open.c
> index 5295e931b0..6ea5dd2457 100644
> --- a/elf/dl-open.c
> +++ b/elf/dl-open.c
> @@ -66,6 +66,9 @@ struct dl_open_args
>       libc_map value in the namespace in case of a dlopen failure.  */
>    bool libc_already_loaded;
>  
> +  /* Set to true if the end of dl_open_worker_begin was reached.  */
> +  bool worker_continue;
> +
>    /* Original parameters to the program and the current environment.  */
>    int argc;
>    char **argv;
> @@ -482,7 +485,7 @@ call_dl_init (void *closure)
>  }
>  
>  static void
> -dl_open_worker (void *a)
> +dl_open_worker_begin (void *a)
>  {
>    struct dl_open_args *args = a;
>    const char *file = args->file;
> @@ -774,6 +777,36 @@ dl_open_worker (void *a)
>        _dl_call_libc_early_init (libc_map, false);
>      }
>  
> +  args->worker_continue = true;
> +}
> +
> +static void
> +dl_open_worker (void *a)
> +{
> +  struct dl_open_args *args = a;
> +
> +  args->worker_continue = false;
> +
> +  {
> +    /* Protects global and module specific TLS state.  */
> +    __rtld_lock_lock_recursive (GL(dl_load_tls_lock));
> +
> +    struct dl_exception ex;
> +    int err = _dl_catch_exception (&ex, dl_open_worker_begin, args);
> +
> +    __rtld_lock_unlock_recursive (GL(dl_load_tls_lock));
> +
> +    if (__glibc_unlikely (ex.errstring != NULL))
> +      /* Reraise the error.  */
> +      _dl_signal_exception (err, &ex, NULL);
> +  }
> +
> +  if (!args->worker_continue)
> +    return;

Why do you need worker_continue?  How can worker_continue not be set at
this point?

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
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