[06/18] linux: Only use 64-bit syscall if required for select
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Commit Message
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).
It also fixes an issue on 32-bit select call for !__ASSUME_PSELECT
(microblase with older kernels only) where the expected timeout
is a 'struct timeval' instead of 'struct timespec'.
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.
---
include/sys/select.h | 5 +++
misc/Makefile | 2 +
misc/tst-select.c | 39 +++++++++++--------
sysdeps/unix/sysv/linux/Makefile | 2 +-
sysdeps/unix/sysv/linux/select.c | 60 ++++++++++--------------------
sysdeps/unix/sysv/linux/select32.c | 58 +++++++++++++++++++++++++++++
6 files changed, 109 insertions(+), 57 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/select32.c
Comments
On Thu, 17 Jun 2021 08:50:52 -0300
Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:
> 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).
>
> It also fixes an issue on 32-bit select call for !__ASSUME_PSELECT
> (microblase with older kernels only) where the expected timeout
> is a 'struct timeval' instead of 'struct timespec'.
>
> 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.
> ---
> include/sys/select.h | 5 +++
> misc/Makefile | 2 +
> misc/tst-select.c | 39 +++++++++++--------
> sysdeps/unix/sysv/linux/Makefile | 2 +-
> sysdeps/unix/sysv/linux/select.c | 60
> ++++++++++-------------------- sysdeps/unix/sysv/linux/select32.c |
> 58 +++++++++++++++++++++++++++++ 6 files changed, 109 insertions(+),
> 57 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/select32.c
>
> diff --git a/include/sys/select.h b/include/sys/select.h
> index ec073deeba..a8961afbed 100644
> --- a/include/sys/select.h
> +++ b/include/sys/select.h
> @@ -21,6 +21,11 @@ extern int __pselect32 (int __nfds, fd_set
> *__readfds, const struct __timespec64 *__timeout,
> const __sigset_t *__sigmask)
> attribute_hidden;
> +extern int __select32 (int __nfds, fd_set *__readfds,
> + fd_set *__writefds, fd_set *__exceptfds,
> + const struct __timespec64 *ts64,
> + struct __timeval64 *timeout)
> + attribute_hidden;
>
> extern int __select64 (int __nfds, fd_set *__readfds,
> fd_set *__writefds, fd_set *__exceptfds,
> diff --git a/misc/Makefile b/misc/Makefile
> index fa40bf0e11..66586bcc7e 100644
> --- a/misc/Makefile
> +++ b/misc/Makefile
> @@ -169,5 +169,7 @@ $(objpfx)tst-allocate_once-mem.out:
> $(objpfx)tst-allocate_once.out $(common-objpfx)malloc/mtrace
> $(objpfx)tst-allocate_once.mtrace > $@; \ $(evaluate-test)
>
> +$(objpfx)tst-select: $(librt)
> +$(objpfx)tst-select-time64: $(librt)
> $(objpfx)tst-pselect: $(librt)
> $(objpfx)tst-pselect-time64: $(librt)
> diff --git a/misc/tst-select.c b/misc/tst-select.c
> index 52aa26651f..134eed99be 100644
> --- a/misc/tst-select.c
> +++ b/misc/tst-select.c
> @@ -17,6 +17,7 @@
> <https://www.gnu.org/licenses/>. */
>
> #include <errno.h>
> +#include <intprops.h>
> #include <support/capture_subprocess.h>
> #include <support/check.h>
> #include <support/support.h>
> @@ -31,12 +32,6 @@ struct child_args
> struct timeval tmo;
> };
>
> -static void
> -alarm_handler (int signum)
> -{
> - /* Do nothing. */
> -}
> -
> static void
> do_test_child (void *clousure)
> {
> @@ -69,17 +64,20 @@ do_test_child (void *clousure)
> static void
> do_test_child_alarm (void *clousure)
> {
> - struct sigaction act = { .sa_handler = alarm_handler };
> - xsigaction (SIGALRM, &act, NULL);
> - alarm (1);
> + struct child_args *args = (struct child_args *) clousure;
>
> - struct timeval tv = { .tv_sec = 10, .tv_usec = 0 };
> + support_create_timer (0, 100000000, false, NULL);
> + struct timeval tv = { .tv_sec = args->tmo.tv_sec, .tv_usec = 0 };
> int r = select (0, NULL, NULL, NULL, &tv);
> TEST_COMPARE (r, -1);
> - TEST_COMPARE (errno, EINTR);
> -
> - if (support_select_modifies_timeout ())
> - TEST_VERIFY (tv.tv_sec < 10);
> + if (args->tmo.tv_sec > INT_MAX)
> + TEST_VERIFY (errno == EINTR || errno == EOVERFLOW);
> + else
> + {
> + TEST_COMPARE (errno, EINTR);
> + if (support_select_modifies_timeout ())
> + TEST_VERIFY (tv.tv_sec < args->tmo.tv_sec);
> + }
> }
>
> static int
> @@ -121,13 +119,24 @@ do_test (void)
> xclose (args.fds[0][0]);
> xclose (args.fds[1][1]);
>
> + args.tmo = (struct timeval) { .tv_sec = 10, .tv_usec = 0 };
> + {
> + struct support_capture_subprocess result;
> + result = support_capture_subprocess (do_test_child_alarm, &args);
> + support_capture_subprocess_check (&result, "tst-select-child", 0,
> + sc_allow_none);
> + }
> +
> + args.tmo = (struct timeval) { .tv_sec = TYPE_MAXIMUM (time_t),
> + .tv_usec = 0 };
> {
> struct support_capture_subprocess result;
> - result = support_capture_subprocess (do_test_child_alarm, NULL);
> + result = support_capture_subprocess (do_test_child_alarm, &args);
> support_capture_subprocess_check (&result, "tst-select-child", 0,
> sc_allow_none);
> }
>
> + args.tmo = (struct timeval) { .tv_sec = 0, .tv_usec = 0 };
> {
> fd_set rfds;
> FD_ZERO (&rfds);
> diff --git a/sysdeps/unix/sysv/linux/Makefile
> b/sysdeps/unix/sysv/linux/Makefile index c36ea0e494..710169a454 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -61,7 +61,7 @@ sysdep_routines += adjtimex clone umount umount2
> readahead sysctl \ open_by_handle_at mlock2 pkey_mprotect pkey_set
> pkey_get \ timerfd_gettime timerfd_settime prctl \
> process_vm_readv process_vm_writev clock_adjtime \
> - time64-support pselect32 \
> + time64-support pselect32 select32 \
> xstat fxstat lxstat xstat64 fxstat64 lxstat64 \
> fxstatat fxstatat64 \
> xmknod xmknodat convert_scm_timestamps
> diff --git a/sysdeps/unix/sysv/linux/select.c
> b/sysdeps/unix/sysv/linux/select.c index dc16a816ed..2d2a7fa720 100644
> --- a/sysdeps/unix/sysv/linux/select.c
> +++ b/sysdeps/unix/sysv/linux/select.c
> @@ -21,7 +21,6 @@
> #include <sys/select.h>
> #include <errno.h>
> #include <sysdep-cancel.h>
> -#include <time64-support.h>
>
> /* Check the first NFDS descriptors each in READFDS (if not NULL)
> for read readiness, in WRITEFDS (if not NULL) for write readiness,
> and in EXCEPTFDS @@ -65,53 +64,32 @@ __select64 (int nfds, fd_set
> *readfds, fd_set *writefds, fd_set *exceptfds, #ifndef
> __NR_pselect6_time64 # define __NR_pselect6_time64 __NR_pselect6
> #endif
> +
> +#ifdef __ASSUME_TIME64_SYSCALLS
> + int r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds,
> exceptfds,
> + pts64, NULL);
> + if (timeout != NULL)
> + TIMESPEC_TO_TIMEVAL (timeout, pts64);
> + return r;
> +#else
> + bool is32bit = timeout != NULL
> + ? in_time_t_range (timeout->tv_sec) : true;
> int r;
> - if (supports_time64 ())
> + if (!is32bit)
> {
> - r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds,
> exceptfds,
> - pts64, NULL);
> - /* Linux by default will update the timeout after a pselect6
> syscall
> - (though the pselect() glibc call suppresses this behavior).
> - Since select() on Linux has the same behavior as the
> pselect6
> - syscall, we update the timeout here. */
> - if (r >= 0 || errno != ENOSYS)
> + r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds,
> + exceptfds, pts64, NULL);
> + if ((r >= 0 || errno != ENOSYS) && timeout != NULL)
> {
> - if (timeout != NULL)
> - TIMESPEC_TO_TIMEVAL (timeout, &ts64);
> - return r;
> + TIMESPEC_TO_TIMEVAL (timeout, &ts64);
> }
> -
> - mark_time64_unsupported ();
> + else
> + __set_errno (EOVERFLOW);
> + return r;
> }
>
> -#ifndef __ASSUME_TIME64_SYSCALLS
> - struct timespec ts32, *pts32 = NULL;
> - if (pts64 != NULL)
> - {
> - if (! in_time_t_range (pts64->tv_sec))
> - {
> - __set_errno (EINVAL);
> - return -1;
> - }
> - ts32.tv_sec = s;
> - ts32.tv_nsec = ns;
> - pts32 = &ts32;
> - }
> -# ifndef __ASSUME_PSELECT
> -# ifdef __NR__newselect
> -# undef __NR_select
> -# define __NR_select __NR__newselect
> -# endif
> - r = SYSCALL_CANCEL (select, nfds, readfds, writefds, exceptfds,
> pts32); -# else
> - r = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
> pts32,
> - NULL);
> -# endif
> - if (timeout != NULL)
> - *timeout = valid_timespec_to_timeval64 (ts32);
> + return __select32 (nfds, readfds, writefds, exceptfds, pts64,
> timeout); #endif
> -
> - return r;
> }
>
> #if __TIMESIZE != 64
> diff --git a/sysdeps/unix/sysv/linux/select32.c
> b/sysdeps/unix/sysv/linux/select32.c new file mode 100644
> index 0000000000..b7e122fe2c
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/select32.c
> @@ -0,0 +1,58 @@
> +/* Synchronous I/O multiplexing. Linux 32-bit time fallback.
> + Copyright (C) 2020-2021 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be
> useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <sys/select.h>
> +#include <sysdep-cancel.h>
> +
> +#ifndef __ASSUME_TIME64_SYSCALLS
> +
> +int
> +__select32 (int nfds, fd_set *readfds, fd_set *writefds,
> + fd_set *exceptfds, const struct __timespec64 *ts64,
> + struct __timeval64 *timeout)
> +{
> +#ifdef __ASSUME_PSELECT
> + struct timespec ts32, *pts32 = NULL;
> + if (ts64 != NULL)
> + {
> + ts32.tv_sec = ts64->tv_sec;
> + ts32.tv_nsec = ts64->tv_nsec;
> + pts32 = &ts32;
> + }
> +
> + int r = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds,
> exceptfds, pts32,
> + NULL);
> + if (timeout != NULL)
> + TIMESPEC_TO_TIMEVAL (timeout, pts32);
> + return r;
> +#else
> + struct timeval tv32, *ptv32 = NULL;
> + if (ts64 != NULL)
> + {
> + tv32 = valid_timespec64_to_timeval (*ts64);
> + ptv32 = &tv32;
> + }
> +
> + int r = SYSCALL_CANCEL (select, nfds, readfds, writefds,
> exceptfds, ptv32);
> + if (timeout != NULL)
> + *timeout = valid_timeval_to_timeval64 (tv32);
> + return r;
> +#endif /* __ASSUME_PSELECT */
> +}
> +
> +#endif
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
@@ -21,6 +21,11 @@ extern int __pselect32 (int __nfds, fd_set *__readfds,
const struct __timespec64 *__timeout,
const __sigset_t *__sigmask)
attribute_hidden;
+extern int __select32 (int __nfds, fd_set *__readfds,
+ fd_set *__writefds, fd_set *__exceptfds,
+ const struct __timespec64 *ts64,
+ struct __timeval64 *timeout)
+ attribute_hidden;
extern int __select64 (int __nfds, fd_set *__readfds,
fd_set *__writefds, fd_set *__exceptfds,
@@ -169,5 +169,7 @@ $(objpfx)tst-allocate_once-mem.out: $(objpfx)tst-allocate_once.out
$(common-objpfx)malloc/mtrace $(objpfx)tst-allocate_once.mtrace > $@; \
$(evaluate-test)
+$(objpfx)tst-select: $(librt)
+$(objpfx)tst-select-time64: $(librt)
$(objpfx)tst-pselect: $(librt)
$(objpfx)tst-pselect-time64: $(librt)
@@ -17,6 +17,7 @@
<https://www.gnu.org/licenses/>. */
#include <errno.h>
+#include <intprops.h>
#include <support/capture_subprocess.h>
#include <support/check.h>
#include <support/support.h>
@@ -31,12 +32,6 @@ struct child_args
struct timeval tmo;
};
-static void
-alarm_handler (int signum)
-{
- /* Do nothing. */
-}
-
static void
do_test_child (void *clousure)
{
@@ -69,17 +64,20 @@ do_test_child (void *clousure)
static void
do_test_child_alarm (void *clousure)
{
- struct sigaction act = { .sa_handler = alarm_handler };
- xsigaction (SIGALRM, &act, NULL);
- alarm (1);
+ struct child_args *args = (struct child_args *) clousure;
- struct timeval tv = { .tv_sec = 10, .tv_usec = 0 };
+ support_create_timer (0, 100000000, false, NULL);
+ struct timeval tv = { .tv_sec = args->tmo.tv_sec, .tv_usec = 0 };
int r = select (0, NULL, NULL, NULL, &tv);
TEST_COMPARE (r, -1);
- TEST_COMPARE (errno, EINTR);
-
- if (support_select_modifies_timeout ())
- TEST_VERIFY (tv.tv_sec < 10);
+ if (args->tmo.tv_sec > INT_MAX)
+ TEST_VERIFY (errno == EINTR || errno == EOVERFLOW);
+ else
+ {
+ TEST_COMPARE (errno, EINTR);
+ if (support_select_modifies_timeout ())
+ TEST_VERIFY (tv.tv_sec < args->tmo.tv_sec);
+ }
}
static int
@@ -121,13 +119,24 @@ do_test (void)
xclose (args.fds[0][0]);
xclose (args.fds[1][1]);
+ args.tmo = (struct timeval) { .tv_sec = 10, .tv_usec = 0 };
+ {
+ struct support_capture_subprocess result;
+ result = support_capture_subprocess (do_test_child_alarm, &args);
+ support_capture_subprocess_check (&result, "tst-select-child", 0,
+ sc_allow_none);
+ }
+
+ args.tmo = (struct timeval) { .tv_sec = TYPE_MAXIMUM (time_t),
+ .tv_usec = 0 };
{
struct support_capture_subprocess result;
- result = support_capture_subprocess (do_test_child_alarm, NULL);
+ result = support_capture_subprocess (do_test_child_alarm, &args);
support_capture_subprocess_check (&result, "tst-select-child", 0,
sc_allow_none);
}
+ args.tmo = (struct timeval) { .tv_sec = 0, .tv_usec = 0 };
{
fd_set rfds;
FD_ZERO (&rfds);
@@ -61,7 +61,7 @@ sysdep_routines += adjtimex clone umount umount2 readahead sysctl \
open_by_handle_at mlock2 pkey_mprotect pkey_set pkey_get \
timerfd_gettime timerfd_settime prctl \
process_vm_readv process_vm_writev clock_adjtime \
- time64-support pselect32 \
+ time64-support pselect32 select32 \
xstat fxstat lxstat xstat64 fxstat64 lxstat64 \
fxstatat fxstatat64 \
xmknod xmknodat convert_scm_timestamps
@@ -21,7 +21,6 @@
#include <sys/select.h>
#include <errno.h>
#include <sysdep-cancel.h>
-#include <time64-support.h>
/* Check the first NFDS descriptors each in READFDS (if not NULL) for read
readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS
@@ -65,53 +64,32 @@ __select64 (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
#ifndef __NR_pselect6_time64
# define __NR_pselect6_time64 __NR_pselect6
#endif
+
+#ifdef __ASSUME_TIME64_SYSCALLS
+ int r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds, exceptfds,
+ pts64, NULL);
+ if (timeout != NULL)
+ TIMESPEC_TO_TIMEVAL (timeout, pts64);
+ return r;
+#else
+ bool is32bit = timeout != NULL
+ ? in_time_t_range (timeout->tv_sec) : true;
int r;
- if (supports_time64 ())
+ if (!is32bit)
{
- r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds, exceptfds,
- pts64, NULL);
- /* Linux by default will update the timeout after a pselect6 syscall
- (though the pselect() glibc call suppresses this behavior).
- Since select() on Linux has the same behavior as the pselect6
- syscall, we update the timeout here. */
- if (r >= 0 || errno != ENOSYS)
+ r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds,
+ exceptfds, pts64, NULL);
+ if ((r >= 0 || errno != ENOSYS) && timeout != NULL)
{
- if (timeout != NULL)
- TIMESPEC_TO_TIMEVAL (timeout, &ts64);
- return r;
+ TIMESPEC_TO_TIMEVAL (timeout, &ts64);
}
-
- mark_time64_unsupported ();
+ else
+ __set_errno (EOVERFLOW);
+ return r;
}
-#ifndef __ASSUME_TIME64_SYSCALLS
- struct timespec ts32, *pts32 = NULL;
- if (pts64 != NULL)
- {
- if (! in_time_t_range (pts64->tv_sec))
- {
- __set_errno (EINVAL);
- return -1;
- }
- ts32.tv_sec = s;
- ts32.tv_nsec = ns;
- pts32 = &ts32;
- }
-# ifndef __ASSUME_PSELECT
-# ifdef __NR__newselect
-# undef __NR_select
-# define __NR_select __NR__newselect
-# endif
- r = SYSCALL_CANCEL (select, nfds, readfds, writefds, exceptfds, pts32);
-# else
- r = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, pts32,
- NULL);
-# endif
- if (timeout != NULL)
- *timeout = valid_timespec_to_timeval64 (ts32);
+ return __select32 (nfds, readfds, writefds, exceptfds, pts64, timeout);
#endif
-
- return r;
}
#if __TIMESIZE != 64
new file mode 100644
@@ -0,0 +1,58 @@
+/* Synchronous I/O multiplexing. Linux 32-bit time fallback.
+ Copyright (C) 2020-2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <sys/select.h>
+#include <sysdep-cancel.h>
+
+#ifndef __ASSUME_TIME64_SYSCALLS
+
+int
+__select32 (int nfds, fd_set *readfds, fd_set *writefds,
+ fd_set *exceptfds, const struct __timespec64 *ts64,
+ struct __timeval64 *timeout)
+{
+#ifdef __ASSUME_PSELECT
+ struct timespec ts32, *pts32 = NULL;
+ if (ts64 != NULL)
+ {
+ ts32.tv_sec = ts64->tv_sec;
+ ts32.tv_nsec = ts64->tv_nsec;
+ pts32 = &ts32;
+ }
+
+ int r = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, pts32,
+ NULL);
+ if (timeout != NULL)
+ TIMESPEC_TO_TIMEVAL (timeout, pts32);
+ return r;
+#else
+ struct timeval tv32, *ptv32 = NULL;
+ if (ts64 != NULL)
+ {
+ tv32 = valid_timespec64_to_timeval (*ts64);
+ ptv32 = &tv32;
+ }
+
+ int r = SYSCALL_CANCEL (select, nfds, readfds, writefds, exceptfds, ptv32);
+ if (timeout != NULL)
+ *timeout = valid_timeval_to_timeval64 (tv32);
+ return r;
+#endif /* __ASSUME_PSELECT */
+}
+
+#endif