Patchwork [RFC,v2,05/20] sysdeps/nanosleep: Use clock_nanosleep_time64 if avaliable

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Submitter Alistair Francis
Date June 25, 2019, 12:08 a.m.
Message ID <d85f6611d45b6c7fea9e82ffcacde71e28625b49.1561421042.git.alistair.francis@wdc.com>
Download mbox | patch
Permalink /patch/33374/
State New
Headers show

Comments

Alistair Francis - June 25, 2019, 12:08 a.m.
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()"

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
---
 ChangeLog                                    |  6 ++++++
 nptl/thrd_sleep.c                            | 19 ++++++++++++++++++-
 sysdeps/unix/sysv/linux/nanosleep.c          | 12 ++++++++++++
 sysdeps/unix/sysv/linux/nanosleep_nocancel.c | 11 +++++++++++
 4 files changed, 47 insertions(+), 1 deletion(-)
Andreas Schwab - June 25, 2019, 8:24 a.m.
There are quite a few style violations (here and in 08/20): braces on
own line, but no braces for single statements; comment style without
asterisks and no parens after functions; argument continuations to line
up after the paren.

Andreas.
arnd@arndb.de - June 25, 2019, 8:59 a.m.
On Tue, Jun 25, 2019 at 2:11 AM Alistair Francis
<alistair.francis@wdc.com> wrote:

> index f14ae565af..c2d6e2f766 100644
> --- a/sysdeps/unix/sysv/linux/nanosleep.c
> +++ b/sysdeps/unix/sysv/linux/nanosleep.c
> @@ -25,7 +25,19 @@ int
>  __nanosleep (const struct timespec *requested_time,
>              struct timespec *remaining)
>  {
> +
> +#ifdef __ASSUME_TIME64_SYSCALLS
> +  return SYSCALL_CANCEL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
> +                         requested_time, remaining);
> +#else
> +# ifdef __NR_clock_nanosleep_time64
> +  long int ret = SYSCALL_CANCEL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
> +                                 requested_time, remaining);
> +  if (ret == 0 || errno != ENOSYS)
> +    return ret;
> +# endif
>    return SYSCALL_CANCEL (nanosleep, requested_time, remaining);
> +#endif
>  }

There has to be a type conversion in here somewhere: If timespec
uses 32-bit time_t (on all existing 32-bit architectures), you must not
pass it into __NR_clock_nanosleep_time64, while on builds with
a 64-bit timespec you must not call nanosleep() without conversion.

I suppose you need something like an internal __nanosleep64 (like
your function above, but with the conversion added to the fallback
path) and an internal __nanosleep32 (not calling clock_nanosleep_time64
or doing conversion). Architectures that have always had a 64-bit time_t
don't need the latter of course.

No idea how that fits into the rest of the glibc implementation.

        Arnd
Alistair Francis - June 26, 2019, 6:20 p.m.
On Tue, Jun 25, 2019 at 1:59 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Tue, Jun 25, 2019 at 2:11 AM Alistair Francis
> <alistair.francis@wdc.com> wrote:
>
> > index f14ae565af..c2d6e2f766 100644
> > --- a/sysdeps/unix/sysv/linux/nanosleep.c
> > +++ b/sysdeps/unix/sysv/linux/nanosleep.c
> > @@ -25,7 +25,19 @@ int
> >  __nanosleep (const struct timespec *requested_time,
> >              struct timespec *remaining)
> >  {
> > +
> > +#ifdef __ASSUME_TIME64_SYSCALLS
> > +  return SYSCALL_CANCEL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
> > +                         requested_time, remaining);
> > +#else
> > +# ifdef __NR_clock_nanosleep_time64
> > +  long int ret = SYSCALL_CANCEL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
> > +                                 requested_time, remaining);
> > +  if (ret == 0 || errno != ENOSYS)
> > +    return ret;
> > +# endif
> >    return SYSCALL_CANCEL (nanosleep, requested_time, remaining);
> > +#endif
> >  }
>
> There has to be a type conversion in here somewhere: If timespec
> uses 32-bit time_t (on all existing 32-bit architectures), you must not
> pass it into __NR_clock_nanosleep_time64, while on builds with
> a 64-bit timespec you must not call nanosleep() without conversion.
>
> I suppose you need something like an internal __nanosleep64 (like
> your function above, but with the conversion added to the fallback
> path) and an internal __nanosleep32 (not calling clock_nanosleep_time64
> or doing conversion). Architectures that have always had a 64-bit time_t
> don't need the latter of course.

Argh, this is a little messy but I think I have something working.

Alistair

>
> No idea how that fits into the rest of the glibc implementation.
>
>         Arnd

Patch

diff --git a/ChangeLog b/ChangeLog
index 05291d7825..b90c5ab60c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@ 
+2019-06-21  Alistair Francis  <alistair.francis@wdc.com>
+
+	* nptl/thrd_sleep.c: Use clock_nanosleep_time64 instead of nanosleep.
+	* sysdeps/unix/sysv/linux/nanosleep.c: Likewise.
+	* sysdeps/unix/sysv/linux/nanosleep_nocancel.c: Likewise.
+
 2019-06-20  Dmitry V. Levin  <ldv@altlinux.org>
 	    Florian Weimer  <fweimer@redhat.com>
 
diff --git a/nptl/thrd_sleep.c b/nptl/thrd_sleep.c
index 07a51808df..09f8c7159f 100644
--- a/nptl/thrd_sleep.c
+++ b/nptl/thrd_sleep.c
@@ -25,7 +25,24 @@  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);
+  int ret;
+
+#ifdef __ASSUME_TIME64_SYSCALLS
+  ret = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err,
+                                 CLOCK_REALTIME, 0, time_point, remaining);
+#else
+# ifdef __NR_clock_nanosleep_time64
+  long int ret_64 = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err,
+                                             CLOCK_REALTIME, 0, time_point, remaining);
+  if (ret_64 == 0 || errno != ENOSYS) {
+    ret = ret_64;
+  } else {
+    ret = INTERNAL_SYSCALL_CANCEL (nanosleep, err, time_point, remaining);
+  }
+# else
+  ret = INTERNAL_SYSCALL_CANCEL (nanosleep, err, time_point, remaining);
+# endif
+#endif
   if (INTERNAL_SYSCALL_ERROR_P (ret, err))
     {
       /* C11 states thrd_sleep function returns -1 if it has been interrupted
diff --git a/sysdeps/unix/sysv/linux/nanosleep.c b/sysdeps/unix/sysv/linux/nanosleep.c
index f14ae565af..c2d6e2f766 100644
--- a/sysdeps/unix/sysv/linux/nanosleep.c
+++ b/sysdeps/unix/sysv/linux/nanosleep.c
@@ -25,7 +25,19 @@  int
 __nanosleep (const struct timespec *requested_time,
 	     struct timespec *remaining)
 {
+
+#ifdef __ASSUME_TIME64_SYSCALLS
+  return SYSCALL_CANCEL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
+                         requested_time, remaining);
+#else
+# ifdef __NR_clock_nanosleep_time64
+  long int ret = SYSCALL_CANCEL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
+                                 requested_time, remaining);
+  if (ret == 0 || errno != ENOSYS)
+    return ret;
+# endif
   return SYSCALL_CANCEL (nanosleep, requested_time, remaining);
+#endif
 }
 hidden_def (__nanosleep)
 weak_alias (__nanosleep, nanosleep)
diff --git a/sysdeps/unix/sysv/linux/nanosleep_nocancel.c b/sysdeps/unix/sysv/linux/nanosleep_nocancel.c
index 122ba627ff..f411a1c6c2 100644
--- a/sysdeps/unix/sysv/linux/nanosleep_nocancel.c
+++ b/sysdeps/unix/sysv/linux/nanosleep_nocancel.c
@@ -24,6 +24,17 @@  int
 __nanosleep_nocancel (const struct timespec *requested_time,
 		      struct timespec *remaining)
 {
+#ifdef __ASSUME_TIME64_SYSCALLS
+  return INLINE_SYSCALL_CALL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
+                         requested_time, remaining);
+#else
+# ifdef __NR_clock_nanosleep_time64
+  long int ret = INLINE_SYSCALL_CALL (clock_nanosleep_time64, CLOCK_REALTIME, 0,
+                                 requested_time, remaining);
+  if (ret == 0 || errno != ENOSYS)
+    return ret;
+# endif
   return INLINE_SYSCALL_CALL (nanosleep, requested_time, remaining);
+#endif
 }
 hidden_def (__nanosleep_nocancel)