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linux: Only use 64-bit syscall if required for ppoll

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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.  This also avoids the need
to use supports_time64() (which breaks the usage case of live migration
like CRIU or similar).

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 2021-06-15 15:41:00 -03:00
parent 92f7b46510
commit ecf2661281
3 changed files with 39 additions and 25 deletions
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9
sysdeps/unix/sysv/linux/Makefile
View File

@ -137,6 +137,15 @@ tests-time64 += \
CFLAGS-tst-sigcontext-get_pc.c = -fasynchronous-unwind-tables
ifeq (yes,$(build-shared))
librt = $(common-objpfx)rt/librt.so
else
librt = $(common-objpfx)rt/librt.a
endif
$(objpfx)tst-ppoll: $(librt)
$(objpfx)tst-ppoll-time64: $(librt)
# Generate the list of SYS_* macros for the system calls (__NR_*
# macros). The file syscall-names.list contains all possible system
# call names, and the generated header file produces SYS_* macros for

34
sysdeps/unix/sysv/linux/ppoll.c
View File

@ -21,9 +21,6 @@
#include <time.h>
#include <sys/poll.h>
#include <sysdep-cancel.h>
#include <kernel-features.h>
#include <time64-support.h>
int
__ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
@ -38,40 +35,33 @@ __ppoll64 (struct pollfd *fds, nfds_t nfds, const struct __timespec64 *timeout,
timeout = &tval;
}
int ret;
if (supports_time64 ())
{
#ifndef __NR_ppoll_time64
# define __NR_ppoll_time64 __NR_ppoll
#endif
#ifdef __ASSUME_TIME64_SYSCALLS
return SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
__NSIG_BYTES);
#else
int ret;
bool need_time64 = timeout != NULL && !in_time_t_range (timeout->tv_sec);
if (need_time64)
{
ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
__NSIG_BYTES);
if (ret == 0 || errno != ENOSYS)
return ret;
mark_time64_unsupported ();
}
#ifndef __ASSUME_TIME64_SYSCALLS
struct timespec ts32;
if (timeout)
{
if (! in_time_t_range (timeout->tv_sec))
{
__set_errno (EOVERFLOW);
return -1;
}
struct timespec ts32;
if (timeout != NULL)
ts32 = valid_timespec64_to_timespec (*timeout);
}
ret = SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
return SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
__NSIG_BYTES);
#endif
return ret;
}
#if __TIMESIZE != 64

15
sysdeps/unix/sysv/linux/tst-ppoll.c
View File

@ -19,9 +19,11 @@
#include <time.h>
#include <poll.h>
#include <errno.h>
#include <intprops.h>
#include <support/check.h>
#include <support/xtime.h>
#include <support/timespec.h>
#include <support/support.h>
#include <stdbool.h>
static int test_ppoll_timeout (bool zero_tmo)
@ -41,6 +43,16 @@ static int test_ppoll_timeout (bool zero_tmo)
return 0;
}
static void
test_ppoll_large_timeout (void)
{
support_create_timer (0, 100000000, false, NULL);
struct timespec ts = { TYPE_MAXIMUM (time_t), 0 };
struct pollfd fds = { -1, 0, 0 };
TEST_COMPARE (ppoll (&fds, 1, &ts, 0), -1);
TEST_VERIFY (errno == EINTR || errno == EOVERFLOW);
}
static int
do_test (void)
{
@ -50,6 +62,9 @@ do_test (void)
/* Check if ppoll exits after specified timeout. */
test_ppoll_timeout (false);
/* Check if ppoll with large timeout. */
test_ppoll_large_timeout ();
return 0;
}