From patchwork Sat Dec 19 03:39:19 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Nicolas S. Dade" X-Patchwork-Id: 559138 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) by ozlabs.org (Postfix) with ESMTP id 88B3B1402A9 for ; Sat, 19 Dec 2015 14:39:41 +1100 (AEDT) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b=VFJq5/8S; dkim-atps=neutral Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 29F123400B; Sat, 19 Dec 2015 03:39:40 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 2v4Q-3ix7CLu; Sat, 19 Dec 2015 03:39:37 +0000 (UTC) Received: from ash.osuosl.org (ash.osuosl.org [140.211.166.34]) by silver.osuosl.org (Postfix) with ESMTP id 7B22D33F5D; Sat, 19 Dec 2015 03:39:37 +0000 (UTC) X-Original-To: uclibc@lists.busybox.net Delivered-To: uclibc@osuosl.org Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by ash.osuosl.org (Postfix) with ESMTP id 5C2DD1CF42D for ; Sat, 19 Dec 2015 03:39:36 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id D43899277F for ; Sat, 19 Dec 2015 03:39:35 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id rLI+3C7TFSEE for ; Sat, 19 Dec 2015 03:39:34 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail-pf0-f181.google.com (mail-pf0-f181.google.com [209.85.192.181]) by whitealder.osuosl.org (Postfix) with ESMTPS id 979D792795 for ; Sat, 19 Dec 2015 03:39:34 +0000 (UTC) Received: by mail-pf0-f181.google.com with SMTP id v86so58284658pfa.2 for ; Fri, 18 Dec 2015 19:39:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=from:to:cc:subject:date:message-id; bh=ANI3Aveeg3x1VvstG4vSb56+Ga3XV6MlCbQGaYIx9ss=; b=VFJq5/8SCVIjvM5DPYSBF5vLnGjsk2pMZ06xW9rXZcNeqqCcTYDzhVoDjGa2Ixf990 hTegLiFLKub/r+8Z3FzX3W7MfnGY/CP5NHGmyBFT4W4ndq7amDjjN0mFWzqhPfsFxODg RaWv5p9SIhSE08MTWUQMcYlsOYd1Sr/qE91WhGyEkzZkSEtQnIQ3He7ITWMogInlflwP fP247Y9ITULR7VAjhh0JVfiQNlqy/e2/ji3RxJMg8UHVHw0IyVnuWcPqxBWyf6LJQPXM rdad+3yt6X2gqBQnZVF3SjFM8QBQtlbyISxvRdlSG5ElJt/7sf1GAGR2yCOZ94JqiphY JDiA== X-Received: by 10.98.89.21 with SMTP id n21mr10443613pfb.70.1450496374399; Fri, 18 Dec 2015 19:39:34 -0800 (PST) Received: from mist-004.mistsys.com (104-10-248-87.lightspeed.sntcca.sbcglobal.net. [104.10.248.87]) by smtp.gmail.com with ESMTPSA id g68sm20584235pfg.9.2015.12.18.19.39.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Fri, 18 Dec 2015 19:39:33 -0800 (PST) From: "Nicolas S. Dade" To: uclibc@uclibc.org Subject: [PATCH] pselect: Use linux pselect syscall when available Date: Fri, 18 Dec 2015 19:39:19 -0800 Message-Id: <1450496359-12069-1-git-send-email-nic.dade@gmail.com> X-Mailer: git-send-email 1.9.1 Cc: "Nicolas S. Dade" X-BeenThere: uclibc@uclibc.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: "Discussion and development of uClibc \(the embedded C library\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: uclibc-bounces@uclibc.org Sender: "uClibc" This supercedes the previous pselect patch from 16 Dec 2015. Linux has a pselect syscall since 2.6.something. Using it rather than emulating it with sigprocmask+select+sigprocmask is smaller code, and works properly. (The emulation has race conditions when unblocked signals arrive before or after the select) The tv.nsec >= 1E9 handling comes from uclibc's linux select() implementation, which itself uses pselect() internally if the pselect syscall exists. I though it would be good to do the same here. Note that although the libc pselect() API has 6 arguments, the linux kernel syscall as 7 arguments. There is an extra, somewhat vestigial, sizeof the signal mask argument. Signed-off-by: Nicolas S. Dade --- libc/sysdeps/linux/common/pselect.c | 52 +++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/libc/sysdeps/linux/common/pselect.c b/libc/sysdeps/linux/common/pselect.c index bf19ce3..3f1dd28 100644 --- a/libc/sysdeps/linux/common/pselect.c +++ b/libc/sysdeps/linux/common/pselect.c @@ -30,6 +30,57 @@ static int __NC(pselect)(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask) { +#ifdef __NR_pselect6 +#define NSEC_PER_SEC 1000000000L + struct timespec _ts, *ts = 0; + if (timeout) { + /* The Linux kernel can in some situations update the timeout value. + * We do not want that so use a local variable. + */ + _ts = *timeout; + + /* GNU extension: allow for timespec values where the sub-sec + * field is equal to or more than 1 second. The kernel will + * reject this on us, so take care of the time shift ourself. + * Some applications (like readline and linphone) do this. + * See 'clarification on select() type calls and invalid timeouts' + * on the POSIX general list for more information. + */ + if (_ts.tv_nsec >= NSEC_PER_SEC) { + _ts.tv_sec += _ts.tv_nsec / NSEC_PER_SEC; + _ts.tv_nsec %= NSEC_PER_SEC; + } + + ts = &_ts; + } + + /* The pselect6 syscall API is strange. It wants a 7th arg to be + * the sizeof(*sigmask). However syscalls with > 6 arguments aren't + * supported on linux. So arguments 6 and 7 are stuffed in a struct + * and a pointer to that struct is passed as the 6th argument to + * the syscall. + * Glibc stuffs arguments 6 and 7 in a ulong[2]. Linux reads + * them as if there were a struct { sigset_t*; size_t } in + * userspace. There woudl be trouble if userspace and the kernel are + * compiled differently enough that size_t isn't the same as ulong, + * but not enough to trigger the compat layer in linux. I can't + * think of such a case, so I'm using linux's struct. + * Furthermore Glibc sets the sigsetsize to _NSIG/8. However linux + * checks for sizeof(sigset_t), which internally is a ulong array. + * This means that if _NSIG isn't a multiple of BITS_PER_LONG then + * linux will refuse glibc's value. So I prefer sizeof(sigset_t) for + * the value of sigsetsize. + */ + struct { + const sigset_t *sigmask; + size_t sigsetsize; + } args67 = { + sigmask, + sizeof(sigset_t), + }; + + return INLINE_SYSCALL(pselect6, 6, nfds, readfds, writefds, exceptfds, ts, &args67); +#else struct timeval tval; int retval; sigset_t savemask; @@ -57,6 +108,7 @@ static int __NC(pselect)(int nfds, fd_set *readfds, fd_set *writefds, sigprocmask (SIG_SETMASK, &savemask, NULL); return retval; +#endif } CANCELLABLE_SYSCALL(int, pselect, (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask),