[PATCH v2 12/19] nptl: Use tidlock when accessing TID on pthread_getcpuclockid

[Florian Weimer]

* Adhemerval Zanella:

> Checked on x86_64-linux-gnu.
> ---
>  nptl/pthread_getcpuclockid.c | 27 +++++++++++++++++----------
>  1 file changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/nptl/pthread_getcpuclockid.c b/nptl/pthread_getcpuclockid.c
> index 0a6656ea4c..8c0db0b9ba 100644
> --- a/nptl/pthread_getcpuclockid.c
> +++ b/nptl/pthread_getcpuclockid.c
> @@ -29,16 +29,23 @@ __pthread_getcpuclockid (pthread_t threadid, clockid_t *clockid)
>    struct pthread *pd = (struct pthread *) threadid;
>  
>    /* Make sure the descriptor is valid.  */
> -  if (INVALID_TD_P (pd))
> -    /* Not a valid thread handle.  */
> -    return ESRCH;
> -
> -  /* The clockid_t value is a simple computation from the TID.  */
> -
> -  const clockid_t tidclock = MAKE_THREAD_CPUCLOCK (pd->tid, CPUCLOCK_SCHED);
> -
> -  *clockid = tidclock;
> -  return 0;
> +  sigset_t oldmask;
> +  __libc_signal_block_all (&oldmask);
> +  lll_lock (pd->tidlock, LLL_PRIVATE);
> +
> +  int res;
> +  if (pd->tid != 0)
> +    {
> +      *clockid = MAKE_THREAD_CPUCLOCK (pd->tid, CPUCLOCK_SCHED);
> +      res = 0;
> +    }
> +  else
> +    res = -ESRCH;
> +
> +  lll_unlock (pd->tidlock, LLL_PRIVATE);
> +  __libc_signal_restore_set (&oldmask);
> +
> +  return res;

This doesn't really solve the race, does it?  The caller cannot use the
clock ID safely.

Thanks,
Florian