From 4c3df0eba5e8fe98f0de917ade9b2ebba6951c5f Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Tue, 15 Jun 2021 21:00:50 -0300 Subject: [PATCH] linux: Only use 64-bit syscall if required for select 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. Reviewed-by: Lukasz Majewski --- include/sys/select.h | 5 +++ misc/Makefile | 2 ++ misc/tst-select.c | 39 +++++++++++++--------- sysdeps/unix/sysv/linux/select.c | 72 +++++++++++++++++++++------------------- 4 files changed, 68 insertions(+), 50 deletions(-) diff --git a/include/sys/select.h b/include/sys/select.h index ec073de..a8961af 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 fa40bf0..66586bc 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 52aa266..134eed9 100644 --- a/misc/tst-select.c +++ b/misc/tst-select.c @@ -17,6 +17,7 @@ . */ #include +#include #include #include #include @@ -32,12 +33,6 @@ struct child_args }; static void -alarm_handler (int signum) -{ - /* Do nothing. */ -} - -static void do_test_child (void *clousure) { struct child_args *args = (struct child_args *) 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/select.c b/sysdeps/unix/sysv/linux/select.c index dc16a81..da25b4b 100644 --- a/sysdeps/unix/sysv/linux/select.c +++ b/sysdeps/unix/sysv/linux/select.c @@ -21,7 +21,6 @@ #include #include #include -#include /* 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 +64,56 @@ __select64 (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, #ifndef __NR_pselect6_time64 # define __NR_pselect6_time64 __NR_pselect6 #endif - int r; - if (supports_time64 ()) - { - r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds, exceptfds, + +#ifdef __ASSUME_TIME64_SYSCALLS + int 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) + if (timeout != NULL) + TIMESPEC_TO_TIMEVAL (timeout, pts64); + return r; +#else + bool need_time64 = timeout != NULL && !in_time_t_range (timeout->tv_sec); + if (need_time64) + { + int 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 +# ifdef __ASSUME_PSELECT 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; + ts32.tv_sec = pts64->tv_sec; + ts32.tv_nsec = pts64->tv_nsec; 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 + + int r = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, pts32, + NULL); if (timeout != NULL) - *timeout = valid_timespec_to_timeval64 (ts32); -#endif + TIMESPEC_TO_TIMEVAL (timeout, pts32); + return r; +# else + struct timeval tv32, *ptv32 = NULL; + if (pts64 != NULL) + { + tv32 = valid_timespec64_to_timeval (*pts64); + 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 } #if __TIMESIZE != 64 -- 2.7.4