On 11/14/18 7:53 AM, Benjamin Peterson wrote:
Thanks, Benjamin. Patch applied.
Cheers,
Michael
> ---
> man2/futex.2 | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/man2/futex.2 b/man2/futex.2
> index 0d5f69fe8..adb8dab89 100644
> --- a/man2/futex.2
> +++ b/man2/futex.2
> @@ -1756,6 +1756,7 @@ Child (18535) 4
> #define _GNU_SOURCE
> #include <stdio.h>
> #include <errno.h>
> +#include <stdatomic.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <sys/wait.h>
> @@ -1785,22 +1786,19 @@ fwait(int *futexp)
> {
> int s;
>
> - /* __sync_bool_compare_and_swap(ptr, oldval, newval) is a gcc
> - built\-in function. It atomically performs the equivalent of:
> + /* atomic_compare_exchange_strong(ptr, oldval, newval)
> + atomically performs the equivalent of:
>
> - if (*ptr == oldval)
> + if (*ptr == *oldval)
> *ptr = newval;
>
> - It returns true if the test yielded true and *ptr was updated.
> - The alternative here would be to employ the equivalent atomic
> - machine\-language instructions. For further information, see
> - the GCC Manual. */
> + It returns true if the test yielded true and *ptr was updated. */
>
> while (1) {
>
> /* Is the futex available? */
> -
> - if (__sync_bool_compare_and_swap(futexp, 1, 0))
> + const int zero = 0;
> + if (atomic_compare_exchange_strong(futexp, &zero, 1))
> break; /* Yes */
>
> /* Futex is not available; wait */
> @@ -1820,10 +1818,10 @@ fpost(int *futexp)
> {
> int s;
>
> - /* __sync_bool_compare_and_swap() was described in comments above */
> -
> - if (__sync_bool_compare_and_swap(futexp, 0, 1)) {
> + /* atomic_compare_exchange_strong() was described in comments above */
>
> + const int one = 1;
> + if (atomic_compare_exchange_strong(futexp, &one, 0)) {
> s = futex(futexp, FUTEX_WAKE, 1, NULL, NULL, 0);
> if (s == \-1)
> errExit("futex\-FUTEX_WAKE");
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
