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* [glibc] linux: Only use 64-bit syscall if required for internal futex
@ 2021-06-22 15:12 Adhemerval Zanella
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From: Adhemerval Zanella @ 2021-06-22 15:12 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b769b0a2cbe469a42641e52f52484e18575b7f67
commit b769b0a2cbe469a42641e52f52484e18575b7f67
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Wed Jun 16 11:04:47 2021 -0300
linux: Only use 64-bit syscall if required for internal futex
For !__ASSUME_TIME64_SYSCALLS there is no need to issue a 64-bit syscall
if the provided timeout fits in a 32-bit one. The 64-bit usage should
be rare since the timeout is a relative one.
Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel
(with and without --enable-kernel=5.1) and on x86_64-linux-gnu.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Diff:
---
nptl/futex-internal.c | 52 ++++++++++++++++++++++++++++---------------
sysdeps/nptl/futex-internal.h | 24 +++++++++++++-------
2 files changed, 50 insertions(+), 26 deletions(-)
diff --git a/nptl/futex-internal.c b/nptl/futex-internal.c
index 850bf4fd83..e74647a9d4 100644
--- a/nptl/futex-internal.c
+++ b/nptl/futex-internal.c
@@ -32,9 +32,6 @@ __futex_abstimed_wait_common32 (unsigned int* futex_word,
struct timespec ts32, *pts32 = NULL;
if (abstime != NULL)
{
- if (! in_time_t_range (abstime->tv_sec))
- return -EOVERFLOW;
-
ts32 = valid_timespec64_to_timespec (*abstime);
pts32 = &ts32;
}
@@ -52,12 +49,28 @@ __futex_abstimed_wait_common32 (unsigned int* futex_word,
static int
__futex_abstimed_wait_common64 (unsigned int* futex_word,
- unsigned int expected, clockid_t clockid,
+ unsigned int expected, int op,
const struct __timespec64* abstime,
int private, bool cancel)
{
- unsigned int clockbit;
+ if (cancel)
+ return INTERNAL_SYSCALL_CANCEL (futex_time64, futex_word, op, expected,
+ abstime, NULL /* Unused. */,
+ FUTEX_BITSET_MATCH_ANY);
+ else
+ return INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op, expected,
+ abstime, NULL /* Ununsed. */,
+ FUTEX_BITSET_MATCH_ANY);
+}
+
+static int
+__futex_abstimed_wait_common (unsigned int* futex_word,
+ unsigned int expected, clockid_t clockid,
+ const struct __timespec64* abstime,
+ int private, bool cancel)
+{
int err;
+ unsigned int clockbit;
/* Work around the fact that the kernel rejects negative timeout values
despite them being valid. */
@@ -70,16 +83,19 @@ __futex_abstimed_wait_common64 (unsigned int* futex_word,
clockbit = (clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0;
int op = __lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private);
- if (cancel)
- err = INTERNAL_SYSCALL_CANCEL (futex_time64, futex_word, op, expected,
- abstime, NULL /* Unused. */,
- FUTEX_BITSET_MATCH_ANY);
+#ifdef __ASSUME_TIME64_SYSCALLS
+ err = __futex_abstimed_wait_common64 (futex_word, expected, op, abstime,
+ private, cancel);
+#else
+ bool need_time64 = abstime != NULL && !in_time_t_range (abstime->tv_sec);
+ if (need_time64)
+ {
+ err = __futex_abstimed_wait_common64 (futex_word, expected, op, abstime,
+ private, cancel);
+ if (err == -ENOSYS)
+ err = -EOVERFLOW;
+ }
else
- err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op, expected,
- abstime, NULL /* Ununsed. */,
- FUTEX_BITSET_MATCH_ANY);
-#ifndef __ASSUME_TIME64_SYSCALLS
- if (err == -ENOSYS)
err = __futex_abstimed_wait_common32 (futex_word, expected, op, abstime,
private, cancel);
#endif
@@ -109,8 +125,8 @@ __futex_abstimed_wait64 (unsigned int* futex_word, unsigned int expected,
clockid_t clockid,
const struct __timespec64* abstime, int private)
{
- return __futex_abstimed_wait_common64 (futex_word, expected, clockid,
- abstime, private, false);
+ return __futex_abstimed_wait_common (futex_word, expected, clockid,
+ abstime, private, false);
}
libc_hidden_def (__futex_abstimed_wait64)
@@ -120,7 +136,7 @@ __futex_abstimed_wait_cancelable64 (unsigned int* futex_word,
const struct __timespec64* abstime,
int private)
{
- return __futex_abstimed_wait_common64 (futex_word, expected, clockid,
- abstime, private, true);
+ return __futex_abstimed_wait_common (futex_word, expected, clockid,
+ abstime, private, true);
}
libc_hidden_def (__futex_abstimed_wait_cancelable64)
diff --git a/sysdeps/nptl/futex-internal.h b/sysdeps/nptl/futex-internal.h
index 969ab2bf4b..79a366604d 100644
--- a/sysdeps/nptl/futex-internal.h
+++ b/sysdeps/nptl/futex-internal.h
@@ -254,15 +254,23 @@ static __always_inline int
futex_lock_pi64 (int *futex_word, const struct __timespec64 *abstime,
int private)
{
- int err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word,
- __lll_private_flag
- (FUTEX_LOCK_PI, private), 0, abstime);
-#ifndef __ASSUME_TIME64_SYSCALLS
- if (err == -ENOSYS)
+ int err;
+#ifdef __ASSUME_TIME64_SYSCALLS
+ err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word,
+ __lll_private_flag (FUTEX_LOCK_PI, private), 0,
+ abstime);
+#else
+ bool need_time64 = abstime != NULL && !in_time_t_range (abstime->tv_sec);
+ if (need_time64)
+ {
+ err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word,
+ __lll_private_flag (FUTEX_LOCK_PI, private),
+ 0, abstime);
+ if (err == -ENOSYS)
+ err = -EOVERFLOW;
+ }
+ else
{
- if (abstime != NULL && ! in_time_t_range (abstime->tv_sec))
- return EOVERFLOW;
-
struct timespec ts32;
if (abstime != NULL)
ts32 = valid_timespec64_to_timespec (*abstime);
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2021-06-22 15:12 [glibc] linux: Only use 64-bit syscall if required for internal futex Adhemerval Zanella
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