On 10/30/20 1:39 PM, Alejandro Colomar wrote:
> The Linux kernel uses the following:
>
> kernel/futex.c:3778:
> SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
> struct __kernel_timespec __user *, utime, u32 __user *, uaddr2,
> u32, val3)
>
> Since there is no glibc wrapper, use the same types the kernel uses.
Thanks. Patch applied.
Cheers,
Michael
> Signed-off-by: Alejandro Colomar <colomar.6....@gmail.com>
> ---
> man2/futex.2 | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/man2/futex.2 b/man2/futex.2
> index 837adbd25..73de71623 100644
> --- a/man2/futex.2
> +++ b/man2/futex.2
> @@ -26,12 +26,13 @@ futex \- fast user-space locking
> .nf
> .PP
> .B #include <linux/futex.h>
> +.B #include <stdint.h>
> .B #include <sys/time.h>
> .PP
> -.BI "int futex(int *" uaddr ", int " futex_op ", int " val ,
> +.BI "long futex(uint32_t *" uaddr ", int " futex_op ", uint32_t " val ,
> .BI " const struct timespec *" timeout , \
> " \fR /* or: \fBuint32_t \fIval2\fP */"
> -.BI " int *" uaddr2 ", int " val3 );
> +.BI " uint32_t *" uaddr2 ", uint32_t " val3 );
> .fi
> .PP
> .IR Note :
> @@ -581,8 +582,8 @@ any of the two supplied futex words:
> .IP
> .in +4n
> .EX
> -int oldval = *(int *) uaddr2;
> -*(int *) uaddr2 = oldval \fIop\fP \fIoparg\fP;
> +uint32_t oldval = *(uint32_t *) uaddr2;
> +*(uint32_t *) uaddr2 = oldval \fIop\fP \fIoparg\fP;
> futex(uaddr, FUTEX_WAKE, val, 0, 0, 0);
> if (oldval \fIcmp\fP \fIcmparg\fP)
> futex(uaddr2, FUTEX_WAKE, val2, 0, 0, 0);
> @@ -1765,11 +1766,11 @@ Child (18535) 4
> #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \e
> } while (0)
>
> -static int *futex1, *futex2, *iaddr;
> +static uint32_t *futex1, *futex2, *iaddr;
>
> static int
> -futex(int *uaddr, int futex_op, int val,
> - const struct timespec *timeout, int *uaddr2, int val3)
> +futex(uint32_t *uaddr, int futex_op, uint32_t val,
> + const struct timespec *timeout, uint32_t *uaddr2, uint32_t val3)
> {
> return syscall(SYS_futex, uaddr, futex_op, val,
> timeout, uaddr2, val3);
> @@ -1779,9 +1780,9 @@ futex(int *uaddr, int futex_op, int val,
> become 1, and then set the value to 0. */
>
> static void
> -fwait(int *futexp)
> +fwait(uint32_t *futexp)
> {
> - int s;
> + long s;
>
> /* atomic_compare_exchange_strong(ptr, oldval, newval)
> atomically performs the equivalent of:
> @@ -1794,7 +1795,7 @@ fwait(int *futexp)
> while (1) {
>
> /* Is the futex available? */
> - const int one = 1;
> + const uint32_t one = 1;
> if (atomic_compare_exchange_strong(futexp, &one, 0))
> break; /* Yes */
>
> @@ -1811,13 +1812,13 @@ fwait(int *futexp)
> so that if the peer is blocked in fpost(), it can proceed. */
>
> static void
> -fpost(int *futexp)
> +fpost(uint32_t *futexp)
> {
> - int s;
> + long s;
>
> /* atomic_compare_exchange_strong() was described in comments above */
>
> - const int zero = 0;
> + const uint32_t zero = 0;
> if (atomic_compare_exchange_strong(futexp, &zero, 1)) {
> s = futex(futexp, FUTEX_WAKE, 1, NULL, NULL, 0);
> if (s == \-1)
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
