Re: [PATCH v4] sysdeps/nanosleep: Use clock_nanosleep_time64 if avaliable

[Lukasz Majewski <lukma at denx dot de>]

Hi Alistair, Joseph,

> The nanosleep syscall is not supported on newer 32-bit platforms (such
> as RV32). To fix this issue let's use clock_nanosleep_time64 if it is
> avaliable.
> 
> Let's use CLOCK_REALTIME when calling clock_nanosleep_time64 as the
> Linux specification says:
>   "POSIX.1 specifies that nanosleep() should measure time against the
>    CLOCK_REALTIME clock. However, Linux measures the time using the
>    CLOCK_MONOTONIC clock. This probably does not matter, since the
> POSIX.1 specification for clock_settime(2) says that discontinuous
> changes in CLOCK_REALTIME should not affect nanosleep()"
> 
> Let's also expose __clock_nanosleep internally to avoid code
> duplication.
> ---
> This was patch was runtime tested with RV32 and RV64
> It was build tested using the ./scripts/build-many-glibcs.py script.
> 
> I am currently running:
> $ make ; make install ; make check
> tests on native ARM (32-bit) with the following three confiugrations:
>  - 4.19 Kernel and 4.19 Headers
>  - 5.2 Kernel and 4.19 Headers
>  - 5.2 Kernel and 5.2 Headers
> I should have the results tomorrow.
> 
> v4:
>  - Rebase on master
>  - Use __clock_nanosleep to avoid duplicate implementations
>  - Fix the error handling when a syscall fails
> v2:
>  - Explicitly include `#include <kernel-features.h>`
> 
>  include/time.h                            | 23 ++++++++
>  nptl/thrd_sleep.c                         | 25 ++++-----
>  sysdeps/unix/sysv/linux/Versions          |  1 +
>  sysdeps/unix/sysv/linux/clock_nanosleep.c | 68
> +++++++++++++++++++++-- sysdeps/unix/sysv/linux/nanosleep.c       |
> 13 +++-- 5 files changed, 106 insertions(+), 24 deletions(-)
> 
> diff --git a/include/time.h b/include/time.h
> index 8ac58e891b5..e0974309726 100644
> --- a/include/time.h
> +++ b/include/time.h
> @@ -184,6 +184,9 @@ extern struct tm *__tz_convert (__time64_t timer,
> int use_localtime, extern int __nanosleep (const struct timespec
> *__requested_time, struct timespec *__remaining);
>  hidden_proto (__nanosleep)
> +extern int __clock_nanosleep (clockid_t clock_id, int flags,
> +                              const struct timespec *req, struct
> timespec *rem); +libc_hidden_proto (__clock_nanosleep)
>  extern int __getdate_r (const char *__string, struct tm *__resbufp)
>    attribute_hidden;
>  
> @@ -206,6 +209,26 @@ libc_hidden_proto (__difftime64)
>  
>  extern double __difftime (time_t time1, time_t time0);
>  
> +#if __TIMESIZE == 64
> +# define __thrd_sleep_time64 thrd_sleep
> +# define __clock_nanosleep_time64 __clock_nanosleep
> +# define __nanosleep_time64 __nanosleep
> +# define __nanosleep_nocancel_time64 __nanosleep_nocancel
> +#else
> +extern int __thrd_sleep_time64 (const struct __timespec64*
> time_point,
> +                                struct __timespec64* remaining);
> +libc_hidden_proto (__thrd_sleep_time64)
> +extern int __clock_nanosleep_time64 (clockid_t clock_id,
> +                                     int flags, const struct
> __timespec64 *req,
> +                                     struct __timespec64 *rem);
> +libc_hidden_proto (__clock_nanosleep_time64)
> +extern int __nanosleep_time64 (const struct __timespec64
> *requested_time,
> +                                struct __timespec64 *remaining);
> +libc_hidden_proto (__nanosleep_time64)
> +extern int __nanosleep_nocancel_time64 (const struct __timespec64
> *requested_time,
> +                                        struct __timespec64
> *remaining); +libc_hidden_proto (__nanosleep_nocancel_time64)
> +#endif
>  
>  /* Use in the clock_* functions.  Size of the field representing the
>     actual clock ID.  */
> diff --git a/nptl/thrd_sleep.c b/nptl/thrd_sleep.c
> index 2e185dd748e..c865f815eea 100644
> --- a/nptl/thrd_sleep.c
> +++ b/nptl/thrd_sleep.c
> @@ -17,23 +17,18 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #include <time.h>
> -#include <sysdep-cancel.h>
> -
> -#include "thrd_priv.h"
> +#include <errno.h>
>  
>  int
>  thrd_sleep (const struct timespec* time_point, struct timespec*
> remaining) {
> -  INTERNAL_SYSCALL_DECL (err);
> -  int ret = INTERNAL_SYSCALL_CANCEL (nanosleep, err, time_point,
> remaining);
> -  if (INTERNAL_SYSCALL_ERROR_P (ret, err))
> -    {
> -      /* C11 states thrd_sleep function returns -1 if it has been
> interrupted
> -	 by a signal, or a negative value if it fails.  */
> -      ret = INTERNAL_SYSCALL_ERRNO (ret, err);
> -      if (ret == EINTR)
> -	return -1;
> -      return -2;
> -    }
> -  return 0;
> +  int ret = __clock_nanosleep (CLOCK_REALTIME, 0, time_point,
> remaining);

Maybe this is a bit off topic (generic question to 64 bit time support)
- but I'm wondering if we shall not use __clock_nanosleep_time64 here
just from the outset? 

With using __clock_nanosleep() as the internal function, the
architectures with __TIMESIZE != 64 (e.g. ARM32 bit) will not benefit
from having internal glibc support for 64 bit time representation (as
their __clock_nanosleep version uses 32 bit to represent time).

Of course we can stick to __clock_nanosleep, but then those functions
would need to be aliased or (better) renamed in the code before Y2038.

The same situation is with e.g. internal usage of __clock_settime.

> +  /* C11 states thrd_sleep function returns -1 if it has been
> interrupted
> +     by a signal, or a negative value if it fails.  */
> +  switch (ret)
> +  {
> +     case 0:      return 0;
> +     case EINTR:  return -1;
> +     default:     return -2;
> +  }
>  }
> diff --git a/sysdeps/unix/sysv/linux/Versions
> b/sysdeps/unix/sysv/linux/Versions index d385085c611..475abb50040
> 100644 --- a/sysdeps/unix/sysv/linux/Versions
> +++ b/sysdeps/unix/sysv/linux/Versions
> @@ -187,5 +187,6 @@ libc {
>      __sigtimedwait;
>      # functions used by nscd
>      __netlink_assert_response;
> +    __clock_nanosleep;
>    }
>  }
> diff --git a/sysdeps/unix/sysv/linux/clock_nanosleep.c
> b/sysdeps/unix/sysv/linux/clock_nanosleep.c index
> 1f240b8720a..13ea9c6f802 100644 ---
> a/sysdeps/unix/sysv/linux/clock_nanosleep.c +++
> b/sysdeps/unix/sysv/linux/clock_nanosleep.c @@ -16,6 +16,7 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #include <time.h>
> +#include <kernel-features.h>
>  #include <errno.h>
>  
>  #include <sysdep-cancel.h>
> @@ -26,9 +27,11 @@
>  /* We can simply use the syscall.  The CPU clocks are not supported
>     with this function.  */
>  int
> -__clock_nanosleep (clockid_t clock_id, int flags, const struct
> timespec *req,
> -		   struct timespec *rem)
> +__clock_nanosleep_time64 (clockid_t clock_id, int flags, const
   ^^^^^^^^^^^^^^^^^ - just an open question - shall we have the naming
   convention (for this function) following the new syscalls names or
   use e.g. __clock_nanosleep64() ?

> struct __timespec64 *req,
> +                          struct __timespec64 *rem)
>  {
> +  int r = -1;
> +
>    if (clock_id == CLOCK_THREAD_CPUTIME_ID)
>      return EINVAL;
>    if (clock_id == CLOCK_PROCESS_CPUTIME_ID)
> @@ -37,12 +40,67 @@ __clock_nanosleep (clockid_t clock_id, int flags,
> const struct timespec *req, /* If the call is interrupted by a signal
> handler or encounters an error, it returns a positive value similar
> to errno.  */ INTERNAL_SYSCALL_DECL (err);
> -  int r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep, err, clock_id,
> flags,
> -				   req, rem);
> +
> +#ifdef __ASSUME_TIME64_SYSCALLS
> +# ifndef __NR_clock_nanosleep_time64
> +#  define __NR_clock_nanosleep_time64 __NR_clock_nanosleep
> +# endif
> +  r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err, clock_id,
> +                               flags, req, rem);
> +#else
> +# ifdef __NR_clock_nanosleep_time64
> +  long int ret_64;

I think that 'int ret;' would be a bit better.

the clock_nanosleep syscall [1] returns int.

> +
> +  ret_64 = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err,
> clock_id,
> +                                    flags, req, rem);
> +
> +  if (ret_64 == 0 || errno != ENOSYS)
> +    {
> +      return (INTERNAL_SYSCALL_ERROR_P (ret_64, err)
> +              ? INTERNAL_SYSCALL_ERRNO (ret_64, err) : 0);
> +    }
> +# endif /* __NR_clock_nanosleep_time64 */
> +  struct timespec ts32, tr32;
> +
> +  if (! in_time_t_range (req->tv_sec))
> +    {
> +      __set_errno (EOVERFLOW);
> +      return -1;
> +    }
> +
> +  ts32 = valid_timespec64_to_timespec (*req);

The man pages for clock_nanosleep (e.g. [2], [3]) do not mention about
the possibility to have *req equal to NULL, hence I do assume that we
don't need to do it here as well...

> +  r =  INTERNAL_SYSCALL_CANCEL (clock_nanosleep, err, &ts32, &tr32);
> +
> +  if ((r == 0 || errno != ENOSYS) && rem)
> +    *rem = valid_timespec_to_timespec64 (tr32);
> +#endif /* __ASSUME_TIME64_SYSCALLS */
> +
>    return (INTERNAL_SYSCALL_ERROR_P (r, err)
> -	  ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
> +          ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
>  }
>  
> +#if __TIMESIZE != 64
> +int
> +__clock_nanosleep (clockid_t clock_id, int flags, const struct
> timespec *req,
> +                   struct timespec *rem)
> +{
> +  int r;
> +  struct __timespec64 treq64, trem64;
> +
> +  treq64 = valid_timespec_to_timespec64 (*req);
> +  r = __clock_nanosleep_time64 (clock_id, flags, &treq64, &trem64);
> +
> +  if (r == 0 || errno != ENOSYS)
> +    {
> +      if (rem)
> +        *rem = valid_timespec64_to_timespec (trem64);
> +    }
> +
> +  return r;
> +}
> +#endif
> +libc_hidden_def (__clock_nanosleep)
> +
>  versioned_symbol (libc, __clock_nanosleep, clock_nanosleep,
> GLIBC_2_17); /* clock_nanosleep moved to libc in version 2.17;
>     old binaries may expect the symbol version it had in librt.  */
> diff --git a/sysdeps/unix/sysv/linux/nanosleep.c
> b/sysdeps/unix/sysv/linux/nanosleep.c index 6787909248f..30cc26909a7
> 100644 --- a/sysdeps/unix/sysv/linux/nanosleep.c
> +++ b/sysdeps/unix/sysv/linux/nanosleep.c
> @@ -17,15 +17,20 @@
>     <https://www.gnu.org/licenses/>.  */
>  
>  #include <time.h>
> -#include <sysdep-cancel.h>
> -#include <not-cancel.h>
> +#include <errno.h>
>  
>  /* Pause execution for a number of nanoseconds.  */
>  int
>  __nanosleep (const struct timespec *requested_time,
> -	     struct timespec *remaining)
> +             struct timespec *remaining)
>  {
> -  return SYSCALL_CANCEL (nanosleep, requested_time, remaining);
> +  int ret = __clock_nanosleep (CLOCK_REALTIME, 0, requested_time,
> remaining);
> +  if (ret != 0)
> +    {
> +      __set_errno (ret);
> +      return -1;
> +    }
> +  return ret;
>  }
>  hidden_def (__nanosleep)
>  weak_alias (__nanosleep, nanosleep)


Links:

[1] -
https://elixir.bootlin.com/linux/v5.4-rc5/source/kernel/time/posix-timers.c#L1230

[2] - http://man7.org/linux/man-pages/man2/nanosleep.2.html

[3] - https://linux.die.net/man/3/clock_nanosleep

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
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Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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