[04/18] linux: Only use 64-bit syscall if required for ppoll
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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).
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.
---
sysdeps/unix/sysv/linux/Makefile | 9 +++++++
sysdeps/unix/sysv/linux/ppoll.c | 41 +++++++++++------------------
sysdeps/unix/sysv/linux/tst-ppoll.c | 15 +++++++++++
3 files changed, 40 insertions(+), 25 deletions(-)
Comments
On Thu, 17 Jun 2021 08:50:50 -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).
>
> 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.
> ---
> sysdeps/unix/sysv/linux/Makefile | 9 +++++++
> sysdeps/unix/sysv/linux/ppoll.c | 41
> +++++++++++------------------ sysdeps/unix/sysv/linux/tst-ppoll.c |
> 15 +++++++++++ 3 files changed, 40 insertions(+), 25 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/Makefile
> b/sysdeps/unix/sysv/linux/Makefile index 294c366e3b..c36ea0e494 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -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
> diff --git a/sysdeps/unix/sysv/linux/ppoll.c
> b/sysdeps/unix/sysv/linux/ppoll.c index 624f14f517..e1ad316e2e 100644
> --- a/sysdeps/unix/sysv/linux/ppoll.c
> +++ b/sysdeps/unix/sysv/linux/ppoll.c
> @@ -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 +35,34 @@ __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
> + bool is32bit = timeout != NULL
> + ? in_time_t_range (timeout->tv_sec) : true;
> + int ret;
> + if (!is32bit)
> + {
> ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout,
> sigmask, __NSIG_BYTES);
> -
> if (ret == 0 || errno != ENOSYS)
> return ret;
> -
> - mark_time64_unsupported ();
> + __set_errno (EOVERFLOW);
> + return -1;
> }
>
> -#ifndef __ASSUME_TIME64_SYSCALLS
> struct timespec ts32;
> - if (timeout)
> - {
> - if (! in_time_t_range (timeout->tv_sec))
> - {
> - __set_errno (EOVERFLOW);
> - return -1;
> - }
> -
> - ts32 = valid_timespec64_to_timespec (*timeout);
> - }
> + if (timeout != NULL)
> + ts32 = valid_timespec64_to_timespec (*timeout);
>
> - ret = SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL,
> sigmask,
> - __NSIG_BYTES);
> + return SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL,
> sigmask,
> + __NSIG_BYTES);
> #endif
> -
> - return ret;
> }
>
> #if __TIMESIZE != 64
> diff --git a/sysdeps/unix/sysv/linux/tst-ppoll.c
> b/sysdeps/unix/sysv/linux/tst-ppoll.c index 9fe6ad07ce..e21e2fcc72
> 100644 --- a/sysdeps/unix/sysv/linux/tst-ppoll.c
> +++ b/sysdeps/unix/sysv/linux/tst-ppoll.c
> @@ -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;
> }
>
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
@@ -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
@@ -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 +35,34 @@ __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
+ bool is32bit = timeout != NULL
+ ? in_time_t_range (timeout->tv_sec) : true;
+ int ret;
+ if (!is32bit)
+ {
ret = SYSCALL_CANCEL (ppoll_time64, fds, nfds, timeout, sigmask,
__NSIG_BYTES);
-
if (ret == 0 || errno != ENOSYS)
return ret;
-
- mark_time64_unsupported ();
+ __set_errno (EOVERFLOW);
+ return -1;
}
-#ifndef __ASSUME_TIME64_SYSCALLS
struct timespec ts32;
- if (timeout)
- {
- if (! in_time_t_range (timeout->tv_sec))
- {
- __set_errno (EOVERFLOW);
- return -1;
- }
-
- ts32 = valid_timespec64_to_timespec (*timeout);
- }
+ if (timeout != NULL)
+ ts32 = valid_timespec64_to_timespec (*timeout);
- ret = SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
- __NSIG_BYTES);
+ return SYSCALL_CANCEL (ppoll, fds, nfds, timeout ? &ts32 : NULL, sigmask,
+ __NSIG_BYTES);
#endif
-
- return ret;
}
#if __TIMESIZE != 64
@@ -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;
}