From patchwork Thu Nov 14 22:00:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Adhemerval Zanella X-Patchwork-Id: 35895 Received: (qmail 34467 invoked by alias); 14 Nov 2019 22:01:05 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 34454 invoked by uid 89); 14 Nov 2019 22:01:05 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-21.7 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_PASS autolearn=ham version=3.3.1 spammy= X-HELO: mail-qk1-f194.google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:subject:date:message-id:in-reply-to:references; bh=cFbfv53I4uNjuuSzDZWx6UHmVH9SHVzFDWcAGUTWzfw=; b=Ke3tRGtotJ4XCpiNUTE0e0/Ke2qn7OqX/l0lSeYb1BJAVh53B8hWy7B80tYbqS0wUq Jkxnq5INjRH75go5ggLyYiloLLXo4u+etMXcS5JvdmJYq47yiqeD+2KBbF5VfpfnfSzt WlJ46KKMDzq3PsdOY9y71XVwMRdyK2BtOYNOB80FYG21P2LjG0QMD/6RPJUXsPqYPis8 A4KbL+Zxm5R5i6DZ2pBDj1oFAkJH2FdyQuIIovpa1+0Wwqn/5gMehRjUruqg5BXxDGsn 79ugSOuXhWFJwFrFqqQnELqdzO4YLzje64ML7Xrba3/CqkeNJRNbEuuV/vaOVkZlSKqF zkWw== Return-Path: From: Adhemerval Zanella To: libc-alpha@sourceware.org Subject: [PATCH v2] misc: Set generic pselect as ENOSYS Date: Thu, 14 Nov 2019 19:00:56 -0300 Message-Id: <20191114220056.16183-1-adhemerval.zanella@linaro.org> In-Reply-To: References: 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 @@ . */ #include -#include -#include /* For NULL. */ -#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 @@ -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 + . */ + +#include +#include +#include +#include +#include + +#ifndef __ASSUME_PSELECT +# define __pselect __pselect_syscall +#endif + +/* If pselect is supported, just use the Linux generic implementation. */ +#include + +#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 . */ -#include -#include -#include -#include -#include +#include #include - -#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 #endif