From: Carlos O'Donell via Libc-alpha <libc-alpha@sourceware.org>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>,
libc-alpha@sourceware.org, Szabolcs Nagy <szabolcs.nagy@arm.com>,
"H . J . Lu" <hjl.tools@gmail.com>
Cc: Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH v2 04/11] linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn
Date: Wed, 11 Jan 2023 16:44:21 -0500 [thread overview]
Message-ID: <12e296b4-c72d-1198-f7fc-fac70614b46d@redhat.com> (raw)
In-Reply-To: <20221104190112.2566409-5-adhemerval.zanella@linaro.org>
On 11/4/22 15:01, Adhemerval Zanella via Libc-alpha wrote:
> The clone3 flag resets all signal handlers of the child not set to
> SIG_IGN to SIG_DFL. It allows to skip most of the sigaction calls
> to setup child signal handling, where previously a posix_spawn
> has to issue 2 times NSIG sigaction calls (one to obtain the current
> disposition and another to set either SIG_DFL or SIG_IGN).
>
> The expection is POSIX_SPAWN_SETSIGDEF the child still setup the
> signal for the case the disposition is SIG_IGN.
>
> It also need to handle the fallback where clone3 is not available,
> to set the fallback in child. This is done by splitting of
> __clone_internal_fallback from __clone_internal.
>
See original v2 review. Please post v4.
> Checked on x86_64-linux-gnu.
> ---
> include/clone_internal.h | 5 +
> posix/Makefile | 3 +-
> posix/tst-spawn7.c | 179 +++++++++++++++++++++++
> sysdeps/unix/sysv/linux/Makefile | 3 +-
> sysdeps/unix/sysv/linux/clone-internal.c | 37 +++--
> sysdeps/unix/sysv/linux/clone3.h | 7 +
> sysdeps/unix/sysv/linux/spawni.c | 31 ++--
> 7 files changed, 238 insertions(+), 27 deletions(-)
> create mode 100644 posix/tst-spawn7.c
>
> diff --git a/include/clone_internal.h b/include/clone_internal.h
> index 5a48c7caa5..81292b3eb1 100644
> --- a/include/clone_internal.h
> +++ b/include/clone_internal.h
> @@ -26,6 +26,11 @@ 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);
> +/* 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),
> + void *__arg)
> + attribute_hidden;
>
> #ifndef _ISOMAC
> libc_hidden_proto (__clone3)
> diff --git a/posix/Makefile b/posix/Makefile
> index 4d60449426..6e61ce50f2 100644
> --- a/posix/Makefile
> +++ b/posix/Makefile
> @@ -109,7 +109,7 @@ tests := test-errno tstgetopt testfnm runtests runptests \
> tst-glob-tilde test-ssize-max tst-spawn4 bug-regex37 \
> bug-regex38 tst-regcomp-truncated tst-spawn-chdir \
> tst-wordexp-nocmd tst-execveat tst-spawn5 \
> - tst-sched_getaffinity tst-spawn6
> + tst-sched_getaffinity tst-spawn6 tst-spawn7
>
> # Test for the glob symbol version that was replaced in glibc 2.27.
> ifeq ($(have-GLIBC_2.26)$(build-shared),yesyes)
> @@ -291,6 +291,7 @@ tst-spawn-ARGS = -- $(host-test-program-cmd)
> tst-spawn-static-ARGS = $(tst-spawn-ARGS)
> tst-spawn5-ARGS = -- $(host-test-program-cmd)
> tst-spawn6-ARGS = -- $(host-test-program-cmd)
> +tst-spawn7-ARGS = -- $(host-test-program-cmd)
> tst-dir-ARGS = `pwd` `cd $(common-objdir)/$(subdir); pwd` `cd $(common-objdir); pwd` $(objpfx)tst-dir
> tst-chmod-ARGS = $(objdir)
> tst-vfork3-ARGS = --test-dir=$(objpfx)
> diff --git a/posix/tst-spawn7.c b/posix/tst-spawn7.c
> new file mode 100644
> index 0000000000..7cb7347c58
> --- /dev/null
> +++ b/posix/tst-spawn7.c
> @@ -0,0 +1,179 @@
> +/* Tests for posix_spawn signal handling.
> + Copyright (C) 2022 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
> + <http://www.gnu.org/licenses/>. */
> +
> +#include <assert.h>
> +#include <getopt.h>
> +#include <spawn.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <support/check.h>
> +#include <support/xsignal.h>
> +#include <support/xunistd.h>
> +#include <unistd.h>
> +
> +/* Nonzero if the program gets called via `exec'. */
> +#define CMDLINE_OPTIONS \
> + { "restart", no_argument, &restart, 1 },
> +static int restart;
> +
> +/* Hold the four initial argument used to respawn the process, plus the extra
> + '--direct', '--restart', the check type ('SIG_IGN' or 'SIG_DFL'), and a
> + final NULL. */
> +static char *spargs[8];
> +static int check_type_argc;
> +
> +/* Called on process re-execution. */
> +_Noreturn static void
> +handle_restart (int argc, char *argv[])
> +{
> + assert (argc == 1);
> +
> + if (strcmp (argv[0], "SIG_DFL") == 0)
> + {
> + for (int i = 1; i < NSIG; i++)
> + {
> + struct sigaction sa;
> + int r = sigaction (i, NULL, &sa);
> + /* Skip internal signals (such as SIGCANCEL). */
> + if (r == -1)
> + continue;
> + TEST_VERIFY_EXIT (sa.sa_handler == SIG_DFL);
> + }
> + exit (EXIT_SUCCESS);
> + }
> + else if (strcmp (argv[0], "SIG_IGN") == 0)
> + {
> + for (int i = 1; i < NSIG; i++)
> + {
> + struct sigaction sa;
> + int r = sigaction (i, NULL, &sa);
> + /* Skip internal signals (such as SIGCANCEL). */
> + if (r == -1)
> + continue;
> + if (i == SIGUSR1 || i == SIGUSR2)
> + TEST_VERIFY_EXIT (sa.sa_handler == SIG_IGN);
> + else
> + TEST_VERIFY_EXIT (sa.sa_handler == SIG_DFL);
> + }
> + exit (EXIT_SUCCESS);
> + }
> +
> + exit (EXIT_FAILURE);
> +}
> +
> +static void
> +spawn_signal_test (const char *type, const posix_spawnattr_t *attr)
> +{
> + spargs[check_type_argc] = (char*) type;
> +
> + pid_t pid;
> + int status;
> +
> + TEST_COMPARE (posix_spawn (&pid, spargs[0], NULL, attr, spargs, environ), 0);
> + TEST_COMPARE (xwaitpid (pid, &status, 0), pid);
> + TEST_VERIFY (WIFEXITED (status));
> + TEST_VERIFY (!WIFSIGNALED (status));
> + TEST_COMPARE (WEXITSTATUS (status), 0);
> +}
> +
> +static void
> +dummy_sa_handler (int)
> +{
> +}
> +
> +static void
> +do_test_signals (void)
> +{
> + {
> + /* Check if all signals handler are set to SIG_DFL on spawned process. */
> + spawn_signal_test ("SIG_DFL", NULL);
> + }
> +
> + {
> + /* Same as before, but set SIGUSR1 and SIGUSR2 to a handler different than
> + SIG_IGN or SIG_DFL. */
> + struct sigaction sa = { 0 };
> + sa.sa_handler = dummy_sa_handler;
> + xsigaction (SIGUSR1, &sa, NULL);
> + xsigaction (SIGUSR2, &sa, NULL);
> + spawn_signal_test ("SIG_DFL", NULL);
> + }
> +
> + {
> + /* Check if SIG_IGN is keep as is. */
> + struct sigaction sa = { 0 };
> + sa.sa_handler = SIG_IGN;
> + xsigaction (SIGUSR1, &sa, NULL);
> + xsigaction (SIGUSR2, &sa, NULL);
> + spawn_signal_test ("SIG_IGN", NULL);
> + }
> +
> + {
> + /* Check if SIG_IGN handlers are set to SIG_DFL. */
> + posix_spawnattr_t attr;
> + posix_spawnattr_init (&attr);
> + sigset_t mask;
> + sigemptyset (&mask);
> + sigaddset (&mask, SIGUSR1);
> + sigaddset (&mask, SIGUSR2);
> + posix_spawnattr_setsigdefault (&attr, &mask);
> + posix_spawnattr_setflags (&attr, POSIX_SPAWN_SETSIGDEF);
> + spawn_signal_test ("SIG_DFL", &attr);
> + posix_spawnattr_destroy (&attr);
> + }
> +}
> +
> +static int
> +do_test (int argc, char *argv[])
> +{
> + /* We must have either:
> +
> + - one or four parameters if called initially:
> + + argv[1]: path for ld.so optional
> + + argv[2]: "--library-path" optional
> + + argv[3]: the library path optional
> + + argv[4]: the application name
> +
> + - six parameters left if called through re-execution:
> + + argv[1]: the application name
> + + argv[2]: check SIG_IGN/SIG_DFL.
> +
> + * When built with --enable-hardcoded-path-in-tests or issued without
> + using the loader directly. */
> +
> + if (restart)
> + handle_restart (argc - 1, &argv[1]);
> +
> + TEST_VERIFY_EXIT (argc == 2 || argc == 5);
> +
> + int i;
> + for (i = 0; i < argc - 1; i++)
> + spargs[i] = argv[i + 1];
> + spargs[i++] = (char *) "--direct";
> + spargs[i++] = (char *) "--restart";
> + check_type_argc = i++;
> + spargs[i] = NULL;
> +
> +
> + do_test_signals ();
> +
> + return 0;
> +}
> +
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index 60e4cb1521..c183ccd4ab 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -175,8 +175,7 @@ tests-clone-internal = \
> tst-align-clone-internal \
> tst-clone2-internal \
> tst-clone3-internal \
> - tst-getpid1-internal \
> - tst-misalign-clone-internal
> + tst-getpid1-internal
> tests-internal += $(tests-clone-internal)
> tests-static += $(tests-clone-internal)
>
> diff --git a/sysdeps/unix/sysv/linux/clone-internal.c b/sysdeps/unix/sysv/linux/clone-internal.c
> index a71effcbd3..7bc991e033 100644
> --- a/sysdeps/unix/sysv/linux/clone-internal.c
> +++ b/sysdeps/unix/sysv/linux/clone-internal.c
> @@ -44,27 +44,15 @@ _Static_assert (sizeof (struct clone_args) == CLONE_ARGS_SIZE_VER2,
> "sizeof (struct clone_args) != CLONE_ARGS_SIZE_VER2");
>
> int
> -__clone_internal (struct clone_args *cl_args,
> - int (*func) (void *arg), void *arg)
> +__clone_internal_fallback (struct clone_args *cl_args,
> + int (*func) (void *arg), void *arg)
> {
> - int ret;
> -#ifdef HAVE_CLONE3_WRAPPER
> - /* Try clone3 first. */
> - int saved_errno = errno;
> - ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
> - if (ret != -1 || errno != ENOSYS)
> - return ret;
> -
> - /* NB: Restore errno since errno may be checked against non-zero
> - return value. */
> - __set_errno (saved_errno);
> -#endif
> -
> /* Map clone3 arguments to clone arguments. NB: No need to check
> invalid clone3 specific bits in flags nor exit_signal since this
> is an internal function. */
> int flags = cl_args->flags | cl_args->exit_signal;
> void *stack = cast_to_pointer (cl_args->stack);
> + int ret;
>
> #ifdef __ia64__
> ret = __clone2 (func, stack, cl_args->stack_size,
> @@ -88,4 +76,23 @@ __clone_internal (struct clone_args *cl_args,
> return ret;
> }
>
> +
> +int
> +__clone_internal (struct clone_args *cl_args,
> + int (*func) (void *arg), void *arg)
> +{
> +#ifdef HAVE_CLONE3_WRAPPER
> + int saved_errno = errno;
> + int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
> + if (ret != -1 || errno != ENOSYS)
> + return ret;
> +
> + /* NB: Restore errno since errno may be checked against non-zero
> + return value. */
> + __set_errno (saved_errno);
> +#endif
> +
> + return __clone_internal_fallback (cl_args, func, arg);
> +}
> +
> libc_hidden_def (__clone_internal)
> diff --git a/sysdeps/unix/sysv/linux/clone3.h b/sysdeps/unix/sysv/linux/clone3.h
> index 7c7e2cdcb0..7dd42ec2d2 100644
> --- a/sysdeps/unix/sysv/linux/clone3.h
> +++ b/sysdeps/unix/sysv/linux/clone3.h
> @@ -23,6 +23,13 @@
> #include <stddef.h>
> #include <bits/types.h>
>
> +
> +/* Flags for the clone3 syscall. */
> +#define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and
> + reset to SIG_DFL. */
> +#define CLONE_INTO_CGROUP 0x200000000ULL /* Clone into a specific cgroup given
> + the right permissions. */
> +
> /* The unsigned 64-bit and 8-byte aligned integer type. */
> typedef __U64_TYPE __aligned_uint64_t __attribute__ ((__aligned__ (8)));
>
> diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
> index 65ee03c804..ebc3c3e521 100644
> --- a/sysdeps/unix/sysv/linux/spawni.c
> +++ b/sysdeps/unix/sysv/linux/spawni.c
> @@ -66,6 +66,7 @@ struct posix_spawn_args
> ptrdiff_t argc;
> char *const *envp;
> int xflags;
> + bool use_clone3;
> int err;
> };
>
> @@ -104,12 +105,11 @@ __spawni_child (void *arguments)
> const posix_spawnattr_t *restrict attr = args->attr;
> const posix_spawn_file_actions_t *file_actions = args->fa;
>
> - /* The child must ensure that no signal handler are enabled because it shared
> - memory with parent, so the signal disposition must be either SIG_DFL or
> - SIG_IGN. It does by iterating over all signals and although it could
> - possibly be more optimized (by tracking which signal potentially have a
> - signal handler), it might requires system specific solutions (since the
> - sigset_t data type can be very different on different architectures). */
> + /* The child must ensure that no signal handler is enabled because it
> + shares memory with parent, so all signal dispositions must be either
> + SIG_DFL or SIG_IGN. If clone3/CLONE_CLEAR_SIGHAND is used, there is
> + only need to set the defined signals POSIX_SPAWN_SETSIGDEF to SIG_DFL;
> + otherwise, the code iterates over all signals. */
> struct sigaction sa;
> memset (&sa, '\0', sizeof (sa));
>
> @@ -122,7 +122,7 @@ __spawni_child (void *arguments)
> {
> sa.sa_handler = SIG_DFL;
> }
> - else if (__sigismember (&hset, sig))
> + else if (!args->use_clone3 && __sigismember (&hset, sig))
> {
> if (is_internal_signal (sig))
> sa.sa_handler = SIG_IGN;
> @@ -382,12 +382,25 @@ __spawnix (pid_t * pid, const char *file,
> for instance). */
> struct clone_args clone_args =
> {
> - .flags = CLONE_VM | CLONE_VFORK,
> + /* Unsupported flags like CLONE_CLEAR_SIGHAND will be cleared up by
> + __clone_internal_fallback. */
> + .flags = CLONE_CLEAR_SIGHAND | CLONE_VM | CLONE_VFORK,
> .exit_signal = SIGCHLD,
> .stack = (uintptr_t) stack,
> .stack_size = stack_size,
> };
> - new_pid = __clone_internal (&clone_args, __spawni_child, &args);
> +#ifdef HAVE_CLONE3_WRAPPER
> + args.use_clone3 = true;
> + new_pid = __clone3 (&clone_args, sizeof (clone_args), __spawni_child,
> + &args);
> + /* clone3 was added on 5.3 and CLONE_CLEAR_SIGHAND on 5.5. */
> + if (new_pid == -1 && (errno == ENOSYS || errno == EINVAL))
> +#endif
> + {
> + args.use_clone3 = false;
> + new_pid = __clone_internal_fallback (&clone_args, __spawni_child,
> + &args);
> + }
>
> /* It needs to collect the case where the auxiliary process was created
> but failed to execute the file (due either any preparation step or
--
Cheers,
Carlos.
next prev parent reply other threads:[~2023-01-11 21:44 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-04 19:01 [PATCH v2 00/11] Optimize posix_spawn signal setup with clone3 Adhemerval Zanella via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 01/11] linux: Do not reset signal handler in posix_spawn if it is already SIG_DFL Adhemerval Zanella via Libc-alpha
2023-01-11 21:27 ` Carlos O'Donell via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 02/11] linux: Extend internal clone3 documentation Adhemerval Zanella via Libc-alpha
2022-11-07 16:40 ` Szabolcs Nagy via Libc-alpha
2023-01-11 21:35 ` Carlos O'Donell via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 03/11] Linux: Do not align the stack for __clone3 Adhemerval Zanella via Libc-alpha
2023-01-11 21:43 ` Carlos O'Donell via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 04/11] linux: Add clone3 CLONE_CLEAR_SIGHAND optimization to posix_spawn Adhemerval Zanella via Libc-alpha
2023-01-11 21:44 ` Carlos O'Donell via Libc-alpha [this message]
2022-11-04 19:01 ` [PATCH v2 05/11] powerpc64: Add the clone3 wrapper Adhemerval Zanella via Libc-alpha
2022-11-28 16:38 ` Paul E Murphy via Libc-alpha
2022-11-29 20:43 ` Adhemerval Zanella Netto via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 06/11] aarch64: " Adhemerval Zanella via Libc-alpha
2022-11-07 16:14 ` Szabolcs Nagy via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 07/11] s390x: " Adhemerval Zanella via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 08/11] riscv: " Adhemerval Zanella via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 09/11] arm: " Adhemerval Zanella via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 10/11] mips: " Adhemerval Zanella via Libc-alpha
2022-11-04 19:01 ` [PATCH v2 11/11] Linux: optimize clone3 internal usage Adhemerval Zanella via Libc-alpha
2023-01-11 21:45 ` Carlos O'Donell via Libc-alpha
2023-01-11 21:24 ` [PATCH v2 00/11] Optimize posix_spawn signal setup with clone3 Carlos O'Donell via Libc-alpha
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