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linux: Only use 64-bit syscall if required for internal futex

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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>
This commit is contained in:
Adhemerval Zanella 2021-06-16 11:04:47 -03:00
parent b286eca5d4
commit b769b0a2cb
2 changed files with 50 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
nptl/futex-internal.c
View File

@ -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)

24
sysdeps/nptl/futex-internal.h
View File

@ -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);