[glibc] nptl: Extend __futex_abstimed_wait_cancelable64 comment
Adhemerval Zanella
azanella@sourceware.org
Wed Nov 25 14:52:32 GMT 2020
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e77221a523bc07abb4a0141543f6d52e705bd831
commit e77221a523bc07abb4a0141543f6d52e705bd831
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Fri Nov 20 10:58:51 2020 -0300
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>
Diff:
---
sysdeps/nptl/futex-internal.c | 8 ++------
sysdeps/nptl/futex-internal.h | 14 +++++++++++---
2 files changed, 13 insertions(+), 9 deletions(-)
diff --git a/sysdeps/nptl/futex-internal.c b/sysdeps/nptl/futex-internal.c
index 457cd3cd69..e4a14b477c 100644
--- a/sysdeps/nptl/futex-internal.c
+++ b/sysdeps/nptl/futex-internal.c
@@ -25,7 +25,7 @@
#ifndef __ASSUME_TIME64_SYSCALLS
static int
__futex_abstimed_wait_cancelable32 (unsigned int* futex_word,
- unsigned int expected, clockid_t clockid,
+ unsigned int expected, int op,
const struct __timespec64* abstime,
int private)
{
@@ -39,10 +39,6 @@ __futex_abstimed_wait_cancelable32 (unsigned int* futex_word,
pts32 = &ts32;
}
- unsigned int clockbit = (clockid == CLOCK_REALTIME)
- ? FUTEX_CLOCK_REALTIME : 0;
- int op = __lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private);
-
return INTERNAL_SYSCALL_CANCEL (futex, futex_word, op, expected,
pts32, NULL /* Unused. */,
FUTEX_BITSET_MATCH_ANY);
@@ -119,7 +115,7 @@ __futex_abstimed_wait_cancelable64 (unsigned int* futex_word,
#ifndef __ASSUME_TIME64_SYSCALLS
if (err == -ENOSYS)
err = __futex_abstimed_wait_cancelable32 (futex_word, expected,
- clockid, abstime, private);
+ op, abstime, private);
#endif
switch (err)
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,
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