nptl: Extend __futex_abstimed_wait_cancelable64 comment

And add a small optimization to avoid setting the operation for the
32-bit time fallback operation.

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Lukasz Majewski <lukma@denx.de>

1 files changed, 11 insertions, 3 deletions

diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
index d5f13d15fb..8c1d592308 100644
--- a/sysdeps/nptl/futex-internal.h
+++ b/sysdeps/nptl/futex-internal.h
@@ -390,9 +390,17 @@ futex_unlock_pi (unsigned int *futex_word, int private)
     }
 }
 
-/* The futex_abstimed_wait_cancelable64 has been moved to a separate file
-   to avoid problems with exhausting available registers on some architectures
-   - e.g. on m68k architecture.  */
+/* Like futex_wait, but will eventually time out (i.e., stop being blocked)
+   after the duration of time provided (i.e., ABSTIME) has passed using the
+   clock specified by CLOCKID (currently only CLOCK_REALTIME and
+   CLOCK_MONOTONIC, the ones support by lll_futex_supported_clockid). ABSTIME
+   can also equal NULL, in which case this function behaves equivalent to
+   futex_wait.
+
+   Returns the same values as futex_wait under those same conditions;
+   additionally, returns ETIMEDOUT if the timeout expired.
+
+   The call acts as a cancellation entrypoint.  */
 int
 __futex_abstimed_wait_cancelable64 (unsigned int* futex_word,
                                     unsigned int expected, clockid_t clockid,