[PATCH v2 2/3] Y2038: nptl: Provide futex_abstimed_wait64 supporting 64 bit time
Lukasz Majewski
lukma@denx.de
Tue Sep 29 16:55:58 GMT 2020
Dear Community,
> This is the helper function, which uses struct __timespec64
> to provide 64 bit absolute time to futex syscalls.
>
> The aim of this function is to move convoluted pre-processor
> macro code from sysdeps/nptl/lowlevellock-futex.h to C
> function in futex-internal.c
>
> The futex_abstimed_wait64 function has been put into a separate
> file on the purpose - to avoid issues apparent on the m68k
> architecture related to small number of available registers (there
> is not enough registers to put all necessary arguments in them if
> the above function would be added to futex-internal.h with
> __always_inline attribute).
>
> Additional precautions for m68k port have been taken - the
> futex-internal.c file will be compiled with -fno-inline flag.
>
Do we have more comments regarding this patch? Or shall I pull it to
-master?
> ---
> Changes for v2:
> - Handle the case when *abstime pointer is NULL
> ---
> sysdeps/nptl/futex-internal.c | 70
> +++++++++++++++++++++++++++ sysdeps/nptl/futex-internal.h |
> 6 +++ sysdeps/unix/sysv/linux/m68k/Makefile | 2 +
> 3 files changed, 78 insertions(+)
>
> diff --git a/sysdeps/nptl/futex-internal.c
> b/sysdeps/nptl/futex-internal.c index 3366aac162..3211b4c94f 100644
> --- a/sysdeps/nptl/futex-internal.c
> +++ b/sysdeps/nptl/futex-internal.c
> @@ -45,6 +45,29 @@ __futex_abstimed_wait_cancelable32 (unsigned int*
> futex_word, abstime != NULL ? &ts32 : NULL,
> NULL /* Unused. */,
> FUTEX_BITSET_MATCH_ANY); }
> +
> +static int
> +__futex_abstimed_wait32 (unsigned int* futex_word,
> + unsigned int expected, clockid_t clockid,
> + const struct __timespec64* abstime,
> + int private)
> +{
> + struct timespec ts32;
> +
> + if (abstime != NULL && ! in_time_t_range (abstime->tv_sec))
> + return -EOVERFLOW;
> +
> + unsigned int clockbit = (clockid == CLOCK_REALTIME) ?
> + FUTEX_CLOCK_REALTIME : 0;
> + int op = __lll_private_flag (FUTEX_WAIT_BITSET | clockbit,
> private); +
> + if (abstime != NULL)
> + ts32 = valid_timespec64_to_timespec (*abstime);
> +
> + return INTERNAL_SYSCALL_CALL (futex, futex_word, op, expected,
> + abstime != NULL ? &ts32 : NULL,
> + NULL /* Unused. */,
> FUTEX_BITSET_MATCH_ANY); +}
> #endif
>
> int
> @@ -97,3 +120,50 @@ __futex_abstimed_wait_cancelable64 (unsigned int*
> futex_word, futex_fatal_error ();
> }
> }
> +
> +int
> +__futex_abstimed_wait64 (unsigned int* futex_word, unsigned int
> expected,
> + clockid_t clockid,
> + const struct __timespec64* abstime, int
> private) +{
> + unsigned int clockbit;
> + int err;
> +
> + /* Work around the fact that the kernel rejects negative timeout
> values
> + despite them being valid. */
> + if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
> + return ETIMEDOUT;
> +
> + if (! lll_futex_supported_clockid(clockid))
> + return EINVAL;
> +
> + clockbit = (clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0;
> + int op = __lll_private_flag (FUTEX_WAIT_BITSET | clockbit,
> private); +
> + err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op,
> expected,
> + abstime, NULL /* Unused. */,
> + FUTEX_BITSET_MATCH_ANY);
> +#ifndef __ASSUME_TIME64_SYSCALLS
> + if (err == -ENOSYS)
> + err = __futex_abstimed_wait32 (futex_word, expected,
> + clockid, abstime, private);
> +#endif
> + switch (err)
> + {
> + case 0:
> + case -EAGAIN:
> + case -EINTR:
> + case -ETIMEDOUT:
> + return -err;
> +
> + case -EFAULT: /* Must have been caused by a glibc or application
> bug. */
> + case -EINVAL: /* Either due to wrong alignment, unsupported
> + clockid or due to the timeout not being
> + normalized. Must have been caused by a glibc or
> + application bug. */
> + case -ENOSYS: /* Must have been caused by a glibc bug. */
> + /* No other errors are documented at this time. */
> + default:
> + futex_fatal_error ();
> + }
> +}
> diff --git a/sysdeps/nptl/futex-internal.h
> b/sysdeps/nptl/futex-internal.h index 7f3910ad98..1ba0d61938 100644
> --- a/sysdeps/nptl/futex-internal.h
> +++ b/sysdeps/nptl/futex-internal.h
> @@ -529,4 +529,10 @@ __futex_abstimed_wait_cancelable64 (unsigned
> int* futex_word, const struct __timespec64* abstime,
> int private) attribute_hidden;
>
> +int
> +__futex_abstimed_wait64 (unsigned int* futex_word, unsigned int
> expected,
> + clockid_t clockid,
> + const struct __timespec64* abstime,
> + int private) attribute_hidden;
> +
> #endif /* futex-internal.h */
> diff --git a/sysdeps/unix/sysv/linux/m68k/Makefile
> b/sysdeps/unix/sysv/linux/m68k/Makefile index be40fae68a..65164c5752
> 100644 --- a/sysdeps/unix/sysv/linux/m68k/Makefile
> +++ b/sysdeps/unix/sysv/linux/m68k/Makefile
> @@ -21,3 +21,5 @@ sysdep-dl-routines += dl-static
> sysdep-others += lddlibc4
> install-bin += lddlibc4
> endif
> +
> +CFLAGS-futex-internal.c += -fno-inline
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
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