From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: libc-alpha@sourceware.org,
Christian Brauner <christian.brauner@ubuntu.com>
Subject: [PATCH 7/7] Linux: optimize clone3 internal usage
Date: Wed, 28 Sep 2022 17:46:34 -0300 [thread overview]
Message-ID: <20220928204634.3036650-8-adhemerval.zanella@linaro.org> (raw)
In-Reply-To: <20220928204634.3036650-1-adhemerval.zanella@linaro.org>
Now that clone3 is used on more architectures, add an optimization
to avoid calling when glibc detects that it is no supported by the
kernel. It also adds __ASSUME_CLONE3, which allows skip this
optimization and issue 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.
---
include/clone_internal.h | 5 +++++
sysdeps/unix/sysv/linux/clone-internal.c | 25 ++++++++++++++++++++++-
sysdeps/unix/sysv/linux/kernel-features.h | 8 ++++++++
3 files changed, 37 insertions(+), 1 deletion(-)
diff --git a/include/clone_internal.h b/include/clone_internal.h
index 320640e64b..71c52211c7 100644
--- a/include/clone_internal.h
+++ b/include/clone_internal.h
@@ -7,6 +7,11 @@ extern __typeof (clone3) __clone3;
-1 with ENOSYS, fall back to clone or clone2. */
extern int __clone_internal (struct clone_args *__cl_args,
int (*__func) (void *__arg), void *__arg);
+/* clone3 wrapper that avoid issuing the syscall once clone3 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 d9eb254ffb..7e20d02025 100644
--- a/sysdeps/unix/sysv/linux/clone-internal.c
+++ b/sysdeps/unix/sysv/linux/clone-internal.c
@@ -76,6 +76,29 @@ __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,
@@ -84,7 +107,7 @@ __clone_internal (struct clone_args *cl_args,
#ifdef HAVE_CLONE3_WRAPPER
/* Try clone3 first. */
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 74adc3956b..496c7f34cb 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -236,4 +236,12 @@
# define __ASSUME_FUTEX_LOCK_PI2 0
#endif
+/* The clone3 system call was introduced across all architectures
+ in Linux 5.3. */
+#if __LINUX_KERNEL_VERSION >= 0x050300
+# define __ASSUME_CLONE3 1
+#else
+# define __ASSUME_CLONE3 0
+#endif
+
#endif /* kernel-features.h */
--
2.34.1
prev parent reply other threads:[~2022-09-28 20:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 20:46 [PATCH 0/7] Optimize posix_spawn signal setup with clone3 Adhemerval Zanella
2022-09-28 20:46 ` [PATCH 1/7] linux: Do set signal handler if it is already SIG_DFL Adhemerval Zanella
2022-09-28 20:46 ` [PATCH 2/7] linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn Adhemerval Zanella
2022-09-28 20:46 ` [PATCH 3/7] powerpc64le: Add the clone3 wrapper Adhemerval Zanella
2022-09-28 20:46 ` [PATCH 4/7] aarch64: " Adhemerval Zanella
2022-09-28 20:46 ` [PATCH 5/7] s390x: " Adhemerval Zanella
2022-09-28 20:46 ` [PATCH 6/7] riscv: " Adhemerval Zanella
2022-09-28 20:46 ` Adhemerval Zanella [this message]
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