| Message ID | 20191114220056.16183-1-adhemerval.zanella@linaro.org |
|---|---|
| State | Accepted |
| Commit | 8781c1301d55db0a95398eb24c11b99205706bae |
| Headers | show |
| Series | [v2] misc: Set generic pselect as ENOSYS | expand |
I will commit this patch with Lukasz Majewski remark if no one opposes. On 14/11/2019 19:00, Adhemerval Zanella wrote: > Changes from previous version: > > - Added some include cleanups. > > - Add the __ASSUME_PSELECT usage on microblaze version. > > -- > > The generic pselect implementation has the very specific race condition > that motived the creation of the pselect syscall (no atomicity in > signal mask set/reset). Using it as generic implementation is > counterproductive Also currently only microblaze uses it as fallback > when used on kernel prior 3.15. > > This patch moves the generic implementation to a microblaze specific > one, sets the generic internal as a ENOSYS, and cleanups the Linux > generic implementation. > > The microblaze implementation mimics the previous Linux generic one, > where it either uses pselect6 directly if __ASSUME_PSELECT or a > first try pselect6 then the fallback otherwise. > > Checked on x86_64-linux-gnu and microblaze-linux-gnu. > --- > misc/pselect.c | 46 +----------- > sysdeps/unix/sysv/linux/microblaze/pselect.c | 73 ++++++++++++++++++++ > sysdeps/unix/sysv/linux/pselect.c | 37 ++-------- > 3 files changed, 80 insertions(+), 76 deletions(-) > create mode 100644 sysdeps/unix/sysv/linux/microblaze/pselect.c > > diff --git a/misc/pselect.c b/misc/pselect.c > index 76ded850a5..b53d9cdcc1 100644 > --- a/misc/pselect.c > +++ b/misc/pselect.c > @@ -17,12 +17,7 @@ > <https://www.gnu.org/licenses/>. */ > > #include <errno.h> > -#include <signal.h> > -#include <stddef.h> /* For NULL. */ > -#include <sys/time.h> > #include <sys/select.h> > -#include <sysdep-cancel.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 > @@ -34,43 +29,8 @@ int > __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, > const struct timespec *timeout, const sigset_t *sigmask) > { > - struct timeval tval; > - int retval; > - sigset_t savemask; > - > - /* Change nanosecond number to microseconds. This might mean losing > - precision and therefore the `pselect` should be available. But > - for now it is hardly found. */ > - if (timeout != NULL) > - { > - /* Catch bugs which would be hidden by the TIMESPEC_TO_TIMEVAL > - computations. The division by 1000 truncates values. */ > - if (__glibc_unlikely (timeout->tv_nsec < 0)) > - { > - __set_errno (EINVAL); > - return -1; > - } > - > - TIMESPEC_TO_TIMEVAL (&tval, timeout); > - } > - > - /* The setting and restoring of the signal mask and the select call > - should be an atomic operation. This can't be done without kernel > - help. */ > - if (sigmask != NULL) > - __sigprocmask (SIG_SETMASK, sigmask, &savemask); > - > - /* Note the pselect() is a cancellation point. But since we call > - select() which itself is a cancellation point we do not have > - to do anything here. */ > - retval = __select (nfds, readfds, writefds, exceptfds, > - timeout != NULL ? &tval : NULL); > - > - if (sigmask != NULL) > - __sigprocmask (SIG_SETMASK, &savemask, NULL); > - > - return retval; > + __set_errno (ENOSYS); > + return -1; > } > -#ifndef __pselect > weak_alias (__pselect, pselect) > -#endif > +stub_warning (pselect) > diff --git a/sysdeps/unix/sysv/linux/microblaze/pselect.c b/sysdeps/unix/sysv/linux/microblaze/pselect.c > new file mode 100644 > index 0000000000..561ff99fb4 > --- /dev/null > +++ b/sysdeps/unix/sysv/linux/microblaze/pselect.c > @@ -0,0 +1,73 @@ > +/* Synchronous I/O multiplexing. Linux/microblaze version. > + Copyright (C) 2019 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 <errno.h> > +#include <signal.h> > +#include <time.h> > +#include <sys/poll.h> > +#include <sysdep-cancel.h> > + > +#ifndef __ASSUME_PSELECT > +# define __pselect __pselect_syscall > +#endif > + > +/* If pselect is supported, just use the Linux generic implementation. */ > +#include <sysdeps/unix/sysv/linux/pselect.c> > + > +#ifndef __ASSUME_PSELECT > +# undef __pselect > +int > +__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, > + const struct timespec *timeout, const sigset_t *sigmask) > +{ > + int ret = __pselect_syscall (nfds, readfds, writefds, exceptfds, timeout, > + sigmask); > + if (ret < 0 && errno != ENOSYS) > + return ret; > + > + /* The fallback uses 'select' which shows the race condition regarding > + signal mask set/restore, requires two additional syscalls, and has > + a worse timeout precision (microseconds instead of nanoseconds). */ > + > + struct timeval tval, *ptval = NULL; > + if (timeout != NULL) > + { > + if (! valid_nanoseconds (timeout->tv_nsec)) > + { > + __set_errno (EINVAL); > + return -1; > + } > + > + TIMESPEC_TO_TIMEVAL (&tval, timeout); > + ptval = &tval; > + } > + > + sigset_t savemask; > + if (sigmask != NULL) > + __sigprocmask (SIG_SETMASK, sigmask, &savemask); > + > + /* select itself is a cancellation entrypoint. */ > + ret = __select (nfds, readfds, writefds, exceptfds, ptval); > + > + if (sigmask != NULL) > + __sigprocmask (SIG_SETMASK, &savemask, NULL); > + > + return ret; > +} > +weak_alias (__pselect, pselect) > +#endif > diff --git a/sysdeps/unix/sysv/linux/pselect.c b/sysdeps/unix/sysv/linux/pselect.c > index acda3e0cdd..7a3dc8c4ed 100644 > --- a/sysdeps/unix/sysv/linux/pselect.c > +++ b/sysdeps/unix/sysv/linux/pselect.c > @@ -16,23 +16,9 @@ > License along with the GNU C Library; if not, see > <https://www.gnu.org/licenses/>. */ > > -#include <errno.h> > -#include <signal.h> > -#include <time.h> > -#include <sys/poll.h> > -#include <kernel-features.h> > +#include <sys/select.h> > #include <sysdep-cancel.h> > > - > -#ifdef __NR_pselect6 > -# ifndef __ASSUME_PSELECT > -static int __generic_pselect (int nfds, fd_set *readfds, fd_set *writefds, > - fd_set *exceptfds, > - const struct timespec *timeout, > - const sigset_t *sigmask); > -# endif > - > - > int > __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, > const struct timespec *timeout, const sigset_t *sigmask) > @@ -59,24 +45,9 @@ __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, > data.ss = (__syscall_ulong_t) (uintptr_t) sigmask; > data.ss_len = _NSIG / 8; > > - int result = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, > - timeout, &data); > - > -# ifndef __ASSUME_PSELECT > - if (result == -1 && errno == ENOSYS) > - result = __generic_pselect (nfds, readfds, writefds, exceptfds, timeout, > - sigmask); > -# endif > - > - return result; > + return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, > + timeout, &data); > } > +#ifndef __pselect > weak_alias (__pselect, pselect) > - > -# ifndef __ASSUME_PSELECT > -# define __pselect static __generic_pselect > -# endif > -#endif > - > -#ifndef __ASSUME_PSELECT > -# include <misc/pselect.c> > #endif >
diff --git a/misc/pselect.c b/misc/pselect.c index 76ded850a5..b53d9cdcc1 100644 --- a/misc/pselect.c +++ b/misc/pselect.c @@ -17,12 +17,7 @@ <https://www.gnu.org/licenses/>. */ #include <errno.h> -#include <signal.h> -#include <stddef.h> /* For NULL. */ -#include <sys/time.h> #include <sys/select.h> -#include <sysdep-cancel.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 @@ -34,43 +29,8 @@ int __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask) { - struct timeval tval; - int retval; - sigset_t savemask; - - /* Change nanosecond number to microseconds. This might mean losing - precision and therefore the `pselect` should be available. But - for now it is hardly found. */ - if (timeout != NULL) - { - /* Catch bugs which would be hidden by the TIMESPEC_TO_TIMEVAL - computations. The division by 1000 truncates values. */ - if (__glibc_unlikely (timeout->tv_nsec < 0)) - { - __set_errno (EINVAL); - return -1; - } - - TIMESPEC_TO_TIMEVAL (&tval, timeout); - } - - /* The setting and restoring of the signal mask and the select call - should be an atomic operation. This can't be done without kernel - help. */ - if (sigmask != NULL) - __sigprocmask (SIG_SETMASK, sigmask, &savemask); - - /* Note the pselect() is a cancellation point. But since we call - select() which itself is a cancellation point we do not have - to do anything here. */ - retval = __select (nfds, readfds, writefds, exceptfds, - timeout != NULL ? &tval : NULL); - - if (sigmask != NULL) - __sigprocmask (SIG_SETMASK, &savemask, NULL); - - return retval; + __set_errno (ENOSYS); + return -1; } -#ifndef __pselect weak_alias (__pselect, pselect) -#endif +stub_warning (pselect) diff --git a/sysdeps/unix/sysv/linux/microblaze/pselect.c b/sysdeps/unix/sysv/linux/microblaze/pselect.c new file mode 100644 index 0000000000..561ff99fb4 --- /dev/null +++ b/sysdeps/unix/sysv/linux/microblaze/pselect.c @@ -0,0 +1,73 @@ +/* Synchronous I/O multiplexing. Linux/microblaze version. + Copyright (C) 2019 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 <errno.h> +#include <signal.h> +#include <time.h> +#include <sys/poll.h> +#include <sysdep-cancel.h> + +#ifndef __ASSUME_PSELECT +# define __pselect __pselect_syscall +#endif + +/* If pselect is supported, just use the Linux generic implementation. */ +#include <sysdeps/unix/sysv/linux/pselect.c> + +#ifndef __ASSUME_PSELECT +# undef __pselect +int +__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, + const struct timespec *timeout, const sigset_t *sigmask) +{ + int ret = __pselect_syscall (nfds, readfds, writefds, exceptfds, timeout, + sigmask); + if (ret < 0 && errno != ENOSYS) + return ret; + + /* The fallback uses 'select' which shows the race condition regarding + signal mask set/restore, requires two additional syscalls, and has + a worse timeout precision (microseconds instead of nanoseconds). */ + + struct timeval tval, *ptval = NULL; + if (timeout != NULL) + { + if (! valid_nanoseconds (timeout->tv_nsec)) + { + __set_errno (EINVAL); + return -1; + } + + TIMESPEC_TO_TIMEVAL (&tval, timeout); + ptval = &tval; + } + + sigset_t savemask; + if (sigmask != NULL) + __sigprocmask (SIG_SETMASK, sigmask, &savemask); + + /* select itself is a cancellation entrypoint. */ + ret = __select (nfds, readfds, writefds, exceptfds, ptval); + + if (sigmask != NULL) + __sigprocmask (SIG_SETMASK, &savemask, NULL); + + return ret; +} +weak_alias (__pselect, pselect) +#endif diff --git a/sysdeps/unix/sysv/linux/pselect.c b/sysdeps/unix/sysv/linux/pselect.c index acda3e0cdd..7a3dc8c4ed 100644 --- a/sysdeps/unix/sysv/linux/pselect.c +++ b/sysdeps/unix/sysv/linux/pselect.c @@ -16,23 +16,9 @@ License along with the GNU C Library; if not, see <https://www.gnu.org/licenses/>. */ -#include <errno.h> -#include <signal.h> -#include <time.h> -#include <sys/poll.h> -#include <kernel-features.h> +#include <sys/select.h> #include <sysdep-cancel.h> - -#ifdef __NR_pselect6 -# ifndef __ASSUME_PSELECT -static int __generic_pselect (int nfds, fd_set *readfds, fd_set *writefds, - fd_set *exceptfds, - const struct timespec *timeout, - const sigset_t *sigmask); -# endif - - int __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask) @@ -59,24 +45,9 @@ __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, data.ss = (__syscall_ulong_t) (uintptr_t) sigmask; data.ss_len = _NSIG / 8; - int result = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, - timeout, &data); - -# ifndef __ASSUME_PSELECT - if (result == -1 && errno == ENOSYS) - result = __generic_pselect (nfds, readfds, writefds, exceptfds, timeout, - sigmask); -# endif - - return result; + return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, + timeout, &data); } +#ifndef __pselect weak_alias (__pselect, pselect) - -# ifndef __ASSUME_PSELECT -# define __pselect static __generic_pselect -# endif -#endif - -#ifndef __ASSUME_PSELECT -# include <misc/pselect.c> #endif