From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1791) id 96E643858D3C; Wed, 1 Feb 2023 12:20:23 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 96E643858D3C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1675254023; bh=yfXxCzFFffsxI2sMPByXmcv6qtvEK2i/G/psmn03XOU=; h=From:To:Subject:Date:From; b=WiYuME/cP5KU6SVtbxTvsO0GUXWxkXEcPWwpWk9xYiZZ1jRInN3hq1GPtfJUhPBZP W4JvMvsIOlO6wrAHCoKTG0sEZ64nuKJ2MYDVFmkdRXcj9ImO8wrv6wWxR4FS36QIqW Ebq/NTIWdtolkZrFwya9M+HUvNGi6VKULQ73JN2M= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Adhemerval Zanella To: glibc-cvs@sourceware.org Subject: [glibc] Linux: optimize clone3 internal usage X-Act-Checkin: glibc X-Git-Author: Adhemerval Zanella Netto X-Git-Refname: refs/heads/master X-Git-Oldrev: 1e442efd57f231bf76030d7a30f2095d1261db20 X-Git-Newrev: 98f9435f336cbee5d57a1a16373331ca1bc648db Message-Id: <20230201122023.96E643858D3C@sourceware.org> Date: Wed, 1 Feb 2023 12:20:22 +0000 (GMT) List-Id: https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=98f9435f336cbee5d57a1a16373331ca1bc648db commit 98f9435f336cbee5d57a1a16373331ca1bc648db Author: Adhemerval Zanella Netto Date: Thu Jan 12 10:58:53 2023 -0300 Linux: optimize clone3 internal usage Add an optimization to avoid calling clone3 when glibc detects that there is no kernel support. It also adds __ASSUME_CLONE3, which allows skipping this optimization and issuing the clone3 syscall directly. It does not handle the the small window between 5.3 and 5.5 for posix_spawn (CLONE_CLEAR_SIGHAND was added in 5.5). Checked on x86_64-linux-gnu. Reviewed-by: Carlos O'Donell Diff: --- include/clone_internal.h | 5 +++++ sysdeps/unix/sysv/linux/clone-internal.c | 24 +++++++++++++++++++++++- sysdeps/unix/sysv/linux/kernel-features.h | 9 +++++++++ 3 files changed, 37 insertions(+), 1 deletion(-) diff --git a/include/clone_internal.h b/include/clone_internal.h index 3b6cd85f02..dd380f119e 100644 --- a/include/clone_internal.h +++ b/include/clone_internal.h @@ -24,6 +24,11 @@ extern int __clone3 (struct clone_args *__cl_args, size_t __size, fall back to clone or clone2. */ extern int __clone_internal (struct clone_args *__cl_args, int (*__func) (void *__arg), void *__arg); +/* clone3 wrapper with a sticky check to avoid re-issuing the syscall if + it fails with ENOSYS. */ +extern int __clone3_internal (struct clone_args *cl_args, + int (*func) (void *args), void *arg) + attribute_hidden; /* The fallback code which calls clone/clone2 based on clone3 arguments. */ extern int __clone_internal_fallback (struct clone_args *__cl_args, int (*__func) (void *__arg), diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c index e125c9125e..790739cfce 100644 --- a/sysdeps/unix/sysv/linux/clone-internal.c +++ b/sysdeps/unix/sysv/linux/clone-internal.c @@ -76,6 +76,28 @@ __clone_internal_fallback (struct clone_args *cl_args, return ret; } +int +__clone3_internal (struct clone_args *cl_args, int (*func) (void *args), + void *arg) +{ +#ifdef HAVE_CLONE3_WRAPPER +# if __ASSUME_CLONE3 + return __clone3 (cl_args, sizeof (*cl_args), func, arg); +# else + static int clone3_supported = 1; + if (atomic_load_relaxed (&clone3_supported) == 1) + { + int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg); + if (ret != -1 || errno != ENOSYS) + return ret; + + atomic_store_relaxed (&clone3_supported, 0); + } +# endif +#endif + __set_errno (ENOSYS); + return -1; +} int __clone_internal (struct clone_args *cl_args, @@ -83,7 +105,7 @@ __clone_internal (struct clone_args *cl_args, { #ifdef HAVE_CLONE3_WRAPPER int saved_errno = errno; - int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg); + int ret = __clone3_internal (cl_args, func, arg); if (ret != -1 || errno != ENOSYS) return ret; diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h index a23d0079a1..4b5c4afbc1 100644 --- a/sysdeps/unix/sysv/linux/kernel-features.h +++ b/sysdeps/unix/sysv/linux/kernel-features.h @@ -241,4 +241,13 @@ # define __ASSUME_FUTEX_LOCK_PI2 0 #endif +/* The clone3 system call was introduced across on most architectures in + Linux 5.3. Not all ports implements it, so it should be used along + HAVE_CLONE3_WRAPPER define. */ +#if __LINUX_KERNEL_VERSION >= 0x050300 +# define __ASSUME_CLONE3 1 +#else +# define __ASSUME_CLONE3 0 +#endif + #endif /* kernel-features.h */